From Mechanisms to Treatment: A Comprehensive View of Lymphatic Metastasis in Cancer

Abstract

The lymphatic system, a complex and dynamic network comprising lymphatic vessels, lymph nodes (LNs), and associated lymphoid tissues, plays a pivotal role in regulating interstitial fluid balance and providing immune surveillance across the body. In cancer, however, the lymphatic system often transforms into a pathway for malignant cell dissemination, leading to lymphatic metastasis—a significant step in tumor progression associated with worse patient prognoses. Mechanistically, tumor cells exploit lymphangiogenic pathways to facilitate their entry and spread within the lymphatic network. Key mechanisms in this process include the upregulation of vascular endothelial growth factors C and D (VEGF-C/D), which promote lymphatic endothelial proliferation, vessel dilation, and increased permeability. This review seeks to provide an in-depth examination of the biological mechanisms underpinning lymphatic metastasis, explore its impact on cancer progression, and highlight current and emerging strategies aimed at managing metastatic disease.

1. Introduction

The lymphatic system, a complex and dynamic network comprising lymphatic vessels, lymph nodes (LNs), and associated lymphoid tissues, plays a pivotal role in regulating interstitial fluid balance and providing immune surveillance across the body [1]. This intricate system serves as a conduit for transporting lymph—a fluid rich in immune cells, cytokines, and signaling molecules—essential for the activation and modulation of immune responses [2]. The primary function of this system centers around maintaining tissue fluid homeostasis, immune cell trafficking, and the filtration of pathogens and antigens through lymph nodes, which in turn initiates and amplifies immune responses [2].

In cancer, however, the lymphatic system often transforms into a pathway for malignant cell dissemination, leading to lymphatic metastasis—a significant step in tumor progression associated with worse patient prognoses [3,4]. Lymphatic metastasis refers to the spread of malignant cells from a primary tumor through lymphatic channels, resulting in colonization of regional lymph nodes and often facilitating further spread to distant organs via lymphatic and bloodborne routes [5] This process marks a critical stage of disease advancement and is implicated in worse outcomes in cancers like breast cancer, melanoma, and gastrointestinal malignancies, where lymph node involvement heavily influences clinical staging, treatment planning, and prognosis [2].

Mechanistically, tumor cells exploit lymphangiogenic pathways to facilitate their entry and spread within the lymphatic network. Key mechanisms in this process include the upregulation of vascular endothelial growth factors C and D (VEGF-C/D), which promote lymphatic endothelial proliferation, vessel dilation, and increased permeability [6,7]. Such lymphangiogenic signaling creates an environment conducive to tumor cell invasion, migration, and colonization of lymph nodes [3,8]. The activation of these pathways not only facilitates local lymphatic spread but also primes tumor cells for further systemic dissemination, underscoring the significance of lymphatic involvement in cancer metastasis [9].

The clinical implications of lymphatic metastasis are profound, with lymph node positivity serving as a critical prognostic marker in cancer staging and treatment planning [10]. The presence of metastatic lymph nodes often correlates with increased risks of distant metastasis and diminished survival, making accurate assessment of lymphatic spread vital for therapeutic decision making [2]. Consequently, advances in diagnostic imaging, sentinel lymph node biopsy, and lymphatic-targeted therapies have emerged as key strategies to identify, stage, and inhibit metastatic progression [4].

This review seeks to provide an in-depth examination of the biological mechanisms underpinning lymphatic metastasis, explore its impact on cancer progression, and highlight current and emerging strategies aimed at managing metastatic disease. By delving into the molecular pathways, diagnostic innovations, and therapeutic interventions targeting lymphatic dissemination, we aim to contribute to the growing body of research and inspire further exploration of this critical aspect of oncology.

2. Mechanisms of Lymphatic Metastasis

2.1. Role of Lymphangiogenesis

Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing ones, is a key process implicated in both physiological functions and pathological conditions, including cancer metastasis. The lymphatic system maintains fluid homeostasis and immune responses but also provides a route for tumor cell dissemination. This process is significant, as it enables cancer cells to invade and spread to lymph nodes and beyond, contributing to disease progression and poor prognosis across multiple cancer types [11].

The link between lymphangiogenesis and lymphatic metastasis is primarily driven by the overexpression of VEGF-C and VEGF-D. These growth factors bind to their receptor VEGFR-3, expressed on lymphatic endothelial cells (LECs), to promote lymphatic vessel sprouting, expansion, and remodeling, creating a favorable environment for tumor cell entry and dissemination (Figure 1) [12]. This results in the formation of peritumoral lymphatic vessels, which are often dilated and more prone to facilitating tumor cell intravasation and transport to lymph nodes [5]. Tumors overexpressing VEGF-C have been shown to exhibit increased lymphatic vessel density and a higher rate of lymph node metastasis through VEGFR-3 signaling, which regulates lymphatic vessel growth, migration, and permeability, creating conditions conducive to tumor spread pathways [13]. VEGF-D plays a complementary role by enhancing lymphangiogenesis through distinct regulatory mechanisms that facilitate metastatic spread [14].

VEGF-C and VEGF-D not only interact with VEGFR-3; they can also form complexes with neuropilin-2, enhancing lymphangiogenic signaling in LECs. Neuropilin-2 co-internalization along with VEGFR-3 suggests an integrated regulatory role where lymphatic vessel signaling pathways are modulated by multiple interactions, promoting precise and efficient lymphatic growth and development [15]. Downstream signaling pathways, such as PI3K/Akt and MAPK, further regulate LEC proliferation, migration, and survival, which extends to pathologies like cancer metastasis (Figure 2) [16]. VEGF-C-induced activation of lymphatic endothelial cells is essential for processes that facilitate tumor dissemination through the lymphatic system [13].

Overall, VEGF-C and VEGF-D signaling pathways are central to the interplay between lymphangiogenesis and lymphatic metastasis. Tumor-secreted VEGF-C and VEGF-D promote lymphatic vessel sprouting and dilation, creating conditions conducive for tumor cell intravasation and subsequent spread to lymph nodes. This lymphatic expansion enhances the metastatic potential of tumors by providing a more accessible route for dissemination, highlighting their potential as therapeutic targets for inhibiting cancer spread (

Table 1. Summary of key mechanisms of lymphatic metastasis and their respective pathways.

Mechanisms of Lymphatic Metastasis
Section	Key Mechanisms/Processes	Molecules/Pathways Involved	Role/Impact
2.1 Role of Lymphangiogenesis	Formation of new lymphatic vessels	VEGF-C, VEGF-D, VEGFR-3, Neuropilin-2	-Promotes lymphatic vessel sprouting, expansion, and remodeling. -Creates favorable conditions for tumor cell intravasation. -VEGF-C/D overexpression increases lymphatic vessel density and metastatic spread.
	Downstream signaling pathways	PI3K/Akt, MAPK	-Regulate lymphatic endothelial cell (LEC) proliferation, migration, and survival. -Support tumor dissemination through lymphatics.
2.2 Tumor Cell Migration and Intravasation Into Lymphatics	Tumor invasion into lymphatics through ECM remodeling and signaling	Chemokines (CCL21-CCR7), MMPs (MMP14, MMP16), adhesion molecules (VCAM-1), CXCL1-integrin β1	-Chemokine gradients (e.g., CCL21-CCR7) guide tumor cells to lymphatic vessels. -MMPs degrade ECM barriers, facilitating migration. -VCAM-1 and integrin signaling enhance permeability and adhesion to lymphatic vessels.
	Synergistic VEGF-C and chemokine signaling	VEGF-C-induced CCL21 secretion, CCR7	-VEGF-C and CCL21 synergize to promote lymphatic vessel dilation and CCR7-dependent tumor invasion. -Enhances metastatic spread to lymph nodes.
2.3 Tumor Cell Survival and Colonization in Lymph Nodes	Immune evasion strategies	Tregs, TGF-β, PD-L1/PD-1 pathway	-Tregs suppress cytotoxic T cells, creating an immunosuppressive microenvironment. -TGF-β inhibits NK and cytotoxic T cell functions. -PD-L1 overexpression blocks T cell activation.
	Adaptation to lymph node microenvironment	Tumor-associated macrophages (TAMs), CAFs, hypoxia, ECM remodeling	-TAMs (M2 phenotype) and CAFs remodel ECM and secrete chemokines, recruiting immunosuppressive cells. -Hypoxia induces genetic changes that enhance survival and resistance to treatment. -Creates a robust niche for tumor persistence.

).

2.2. Tumor Cell Migration and Intravasation into Lymphatics

Continuing from the critical role of lymphangiogenesis in promoting lymphatic metastasis, tumor cell migration and intravasation into lymphatics mark the next steps in metastatic spread. Tumor cells leverage complex interactions within the lymphatic microenvironment to enter lymphatic vessels, a process that is facilitated by chemokines, growth factors, adhesion molecules, and matrix-modifying enzymes (Table 1).

Flow dynamics within lymphatic vessels play a crucial role in modulating tumor cell behavior. Research has demonstrated that both luminal and transmural fluid flow can increase the rate of tumor cell invasion and intravasation by altering the adhesive properties of the lymphatic endothelium. These biomechanical cues act as critical regulators of tumor–lymphatic interactions, enhancing the ability of tumor cells to penetrate the lymphatic barrier [17].

Chemokines, such as CCL21, secreted by lymphatic endothelial cells (LECs), provide directional cues that attract tumor cells expressing the corresponding receptor, CCR7. This chemokine–receptor interaction creates a chemotactic gradient, guiding tumor cells toward lymphatic vessels and facilitating their intravasation. This mechanism is particularly significant in cancers like melanoma, where CCR7-driven migration enhances metastatic spread to lymph nodes [18].

Matrix metalloproteinases (MMPs), particularly MMP14 and MMP16, further enhance tumor cell migration by degrading extracellular matrix (ECM) components (Figure 1). This proteolytic activity not only clears physical barriers to invasion but also modulates cell adhesion dynamics, thereby promoting tumor cell entry into lymphatic vessels. MMP activity underscores the importance of ECM remodeling in facilitating tumor cell dissemination [19,20].

Adhesion molecules expressed by lymphatic endothelial cells also play a pivotal role in the intravasation process. Molecules like VCAM-1, upregulated in tumor-associated lymphatic vessels, weaken the junctional integrity of LECs, thereby increasing lymphatic permeability. This facilitates tumor cell entry into lymphatic vessels, providing a more accessible route for their dissemination [21,22,23].

Additionally, tumor–lymphatic interactions are modulated by chemokine signaling pathways, such as the CXCL1-integrin β1 axis. CXCL1, secreted by tumor-associated LECs, activates integrin signaling pathways in cancer cells, enhancing their migration, invasion, and adhesion to lymphatic vessels. This interaction highlights the complex signaling crosstalk that facilitates lymphatic invasion and promotes metastatic progression (Wang et al., 2017) [24].

The synergistic effects of VEGF-C signaling and CCR7-mediated chemoinvasion further illustrate the multi-faceted strategies employed by tumor cells to invade the lymphatic system. VEGF-C not only promotes lymphangiogenesis but also upregulates lymphatic secretion of CCL21, driving CCR7-dependent tumor cell migration and invasion. This dual role underscores the importance of targeting both chemokine and growth factor pathways in the management of lymphatic metastasis [25].

2.3. Tumor Cell Survival and Colonization in Lymph Nodes

Tumor cell survival and colonization in lymph nodes are critical steps in cancer metastasis driven by complex immune evasion strategies and microenvironmental adaptations. To persist within lymph nodes, tumor cells must escape immune surveillance. One major mechanism involves the recruitment and modulation of regulatory T cells (Tregs) within the tumor microenvironment. Tregs suppress the activity of cytotoxic T cells and other immune effectors, providing essential survival signals to the tumor and creating a protective niche. This suppression not only blunts the host immune response but actively supports tumor persistence and proliferation [26]. Furthermore, tumors frequently secrete immunosuppressive cytokines, such as TGF-β, which inhibit the function of natural killer (NK) cells and cytotoxic T lymphocytes. This TGF-β-mediated immune suppression can be reversed therapeutically to restore NK cell activity, highlighting potential strategies for disrupting immune evasion (Table 1) [27,28].

Tumor cells also exploit immune checkpoint pathways to evade detection. By overexpressing immune checkpoint proteins, such as programmed death-ligand 1 (PD-L1), tumor cells can inhibit T cell activation by binding to programmed cell death protein-1 (PD-1) receptors on immune cells. This interaction effectively blunts immune responses, allowing the tumor to thrive [29,30].

In addition to immune evasion, tumor cells adapt to the supportive microenvironment of the lymph nodes to ensure their survival. The tumor microenvironment (TME) within lymph nodes is a complex network of immune cells, fibroblasts, and structural elements that work together to support tumor growth [31]. Tumor-associated macrophages (TAMs), often polarized towards an immunosuppressive M2 phenotype, promote tumor survival by secreting anti-inflammatory cytokines and remodeling the extracellular matrix (ECM) to create a favorable environment for cancer cells [31,32]. These interactions enable tumor cells to evade immune attack, proliferate, and establish themselves within lymph nodes (Table 1).

Hypoxia within the lymph node microenvironment further drives tumor adaptation by inducing genetic and epigenetic changes that enhance resistance to treatment and promote survival. Cancer-associated fibroblasts (CAFs) and other stromal cells play a critical role in reorganizing the ECM and secreting chemokines that recruit additional immunosuppressive cells, such as Tregs, which bolster immune evasion mechanisms. This interplay between structural and immune components creates a robust niche that fosters tumor colonization and persistence [33,34].

Beyond immune evasion, metabolic adaptations in the lymphatic environment further enhance tumor cell survival and prepare them for subsequent systemic dissemination [35]. Recent studies have shown that the lymphatic system provides a relatively protective biochemical milieu compared to the bloodstream, with higher concentrations of glutathione and oleic acid and lower levels of free iron [35]. These conditions help tumor cells develop resistance to ferroptosis, a form of iron-dependent programmed cell death driven by oxidative stress [35]. Because the bloodstream represents a more oxidative environment, the metabolic conditioning within the lymphatic system enhances tumor cell survival and metastatic competence during later hematogenous spread [35]. Exposure to the lymphatic microenvironment therefore not only facilitates regional dissemination but also equips tumor cells for successful systemic metastasis [35,36].

2.4. Tumor Types and the Role of Lymphatic Metastasis

Solid and hematologic tumors represent two major categories of cancer, each exhibiting distinct patterns of lymphatic involvement [37]. In solid tumors, such as breast cancer, melanoma, colorectal cancer, and non-small cell lung cancer (NSCLC), lymphatic metastasis plays a critical role in disease progression and prognosis [4]. Tumor cells in these cancers often exploit lymphangiogenic pathways to enter lymphatic vessels, colonize regional lymph nodes, and disseminate to distant organs [38]. Lymph node involvement serves as a key prognostic factor and guides treatment decisions, including the use of lymphadenectomy, sentinel lymph node biopsy, and systemic therapies [39].

In contrast, hematologic malignancies, such as lymphoma and leukemia, inherently involve lymphoid tissues and systemic circulation. While the lymphatic structures are central to disease development in these cancers, the concept of lymphatic metastasis differs from solid tumors, as spread through lymphatic channels is a natural component of disease dissemination rather than a secondary process [40]. Nonetheless, disruption of normal lymphatic architecture and function remains a hallmark of advanced disease in hematologic cancers [41].

A summary of representative solid and hematologic tumors and the role of lymphatic metastasis in their progression is provided in

Table 2. Tumor types and the role of lymphatic metastasis.

Tumor Type	Category	Role of Lymphatic Metastasis
Breast Cancer	Solid	Strong predictor of prognosis; lymph node status critical for staging and therapeutic decisions.
Melanoma	Solid	Early lymphatic spread to sentinel nodes; SLN biopsy is standard for staging and management.
Colorectal Cancer	Solid	Lymph node involvement defines stage III disease; lymphatic invasion predicts worse survival.
Non-Small Cell Lung Cancer (NSCLC)	Solid	Lymphatic spread associated with relapse risk; mediastinal node metastasis guides resection and adjuvant therapy.
Gastric Cancer	Solid	Lymphatic dissemination to perigastric and para-aortic nodes affects surgical planning and prognosis.
Cervical Cancer	Solid	Lymphatic invasion correlates with recurrence risk; guides need for radiotherapy and chemotherapy.
Lymphoma	Hematologic	Primary malignancy of lymphatic tissues; dissemination is systemic but disrupts lymphatic architecture.
Leukemia	Hematologic	Involves blood and lymphatic system; lymphadenopathy common but “metastasis” concept differs from solid tumors.

.

3. Clinical Implications of Lymphatic Metastasis

3.1. Prognostic Value of Lymphatic Involvement in Cancer

Lymphatic involvement, as mentioned earlier, has a significant role in cancer metastasis to different locations throughout the body. The presence of cancer in the lymph nodes is a telltale sign and one of the most common sites of metastasis. Moreover, the presence of cancer cells in the lymphatic vessels, or lymphatic invasion, can also be used for prognostic purposes.

The number of lymph nodes positive for cancer greatly influences mean survival. The TNM classification system helps classify a malignancy and consists of the following factors: size and spread, spread to nearby lymph nodes, and metastasis to other parts of the body. This system separates cancer cases into stages to evaluate the severity of the disease and survival probability [42]. This has been implemented in breast cancer, where N1 represents one to three axillary lymph nodes, N2 represents metastasis in four to nine lymph nodes, and N3 represents metastasis in ten or more lymph nodes [43]. Likewise, for colorectal cancer, N1 indicates the involvement of one to three nodes, N2 indicates four to six nodes, and N3 indicates seven or more regional nodes [42]. This practice is also common in prostate cancer and crucial after prostatectomy to allow for histopathology and staging [44]. This tumor staging system, while slightly modified for different types of cancer, still highlights lymph node metastasis as a crucial component with a significant prognostic role in cancer.

Similar to identifying the number of lymph nodes, the implementation of a lymph node ratio has been utilized to control for the number of lymph nodes removed. Diagnosis and treatment can involve the removal of regional lymph nodes to check for and reduce cancer spread [45]. The lymph node ratio represents the ratio of metastatic lymph nodes to examined lymph nodes. This has been found to be more effective than simply counting the number of lymph nodes in breast cancer, colorectal cancer, gastric cancer, pancreatic cancer, and many others [46,47]. For example, in stage III colorectal cancer, a high lymph node ratio had a pooled hazard ratio of 2.36 for overall survival and 3.71 for disease-free survival [48]. Furthermore, the presence of lymph node metastasis was a significant (p < 0.008) prognostic factor in oral and laryngeal squamous cell carcinomas [49].

Lymphatic vessel invasion (LVI) has also been used to help determine the survival of patients with specific cancers. In a study of 1408 patients with breast cancer, the presence of LVI was shown to have an odds ratio of 1.92 for causing death compared to those without LVI. The incidence of LVI was also highly correlated with the number of lymph node metastases and tumor size, two validated prognostic factors [50]. Even when isolated and used in both univariate and multivariate analyses, LVI was significantly shown to be an independent predictor of overall and disease-free survival [51]. Analyses have also shown LVI to have a higher hazard ratio than the presence of one to two positive lymph nodes. Assessment of LVI is now endorsed as a prognostic factor for breast cancer by the World Health Organization, the European Commission, the American Joint Committee on Cancer, and more sources [52]. For prostate cancer, LVI was similarly found to be linked to prostate-specific antigen recurrence. LVI is identified 10.2% of the time on average and is correlated with outcomes, signifying the need for routine screenings of LVI in prostatectomy specimens [52]. LVI status was unrelated to clinical outcomes in patients with metastasis (N1) but implicated in poor outcomes in patients with no metastasis (N0) [44]. LVI has also been shown to be a significant indicator of poor prognosis in colorectal cancer patients, with an overall survival hazard ratio of 2.25 (p < 0.0001) and a disease-free survival hazard ratio of 2.34 (p < 0.0001) [30]. A higher prevalence of LVI in patients with oral cancer was found in patients with advanced-stage cancer with metastases and has a significant negative impact on patient survival; it may be an indication for preventative neck dissection with adjuvant therapy [53,54]. Non-small cell lung cancer is also correlated with lymphatic vessel invasion, with LVI in 32.1% of patients who were 1.73 times more likely to relapse and showed a pooled hazard ratio of 1.59 compared to patients without LVI [55]. Finally, melanoma patients who presented with LVI had greater lymph node involvement (p = 0), a higher Clark level (p = 0), greater ulcerations (p = 0), and more metastasis (p = 0.008). Lymph node metastasis and lymphatic invasion are both promising prognostic markers for cancer metastasis and signify poorer outcomes in various cancer types. Targeted therapy, such as the use of anti-lymphangiogenic for photodynamic ablation, has shown promising results in preventing lymphatic invasion.

3.2. Diagnostic Approaches

Lymphoscintigraphy is an imaging tool used to assess lymphatic function and map out sentinel lymph nodes (SLN), which are the first lymph nodes where cancer can metastasize from the primary tumor. Lymphoscintigraphy uses a radioactive tracer and gamma cameras to visualize the gamma rays released by the tracer [56]. The sentinel lymph node would have a higher count of radioactive tracers in this scenario, enabling its identification using the gamma cameras [57]. The most common tracer used in lymphoscintigraphy is a technetium-99m-labeled lymphatic-specific tracer. Tracers of smaller size have been shown to have rapid uptake, sparking the use of new, smaller tracers for greater dissemination. The tracer is often injected into the interdigital space of the hands or feet, where it can then help localize SLNs using gamma cameras. Classical lymphoscintigraphy provides planar images of low resolution, which cannot provide accurate anatomical details. However, it still has significant uses for both qualitative and quantitative analyses. Qualitative analysis can analyze the symmetry of tracer intake into lymph nodes and identify dermal backflow. Quantitative analysis can calculate the tracer’s disappearance rate, tracer uptake kinetics, or the quantitative asymmetry index [58,59]. Lymphoscintigraphy can also be used in conjunction with SPECT/CT imaging to provide morphological information [60]. Lymphoscintigraphy is widely utilized, prompting new innovative techniques. The current advances in this field include the use of Indocyanine Green, photoacoustic detection, or superparamagnetic iron oxide [61,62,63].

Sentinel lymph node (SLN) biopsy, guided by lymphoscintigraphy, allows for the targeted removal of sentinel lymph nodes, reducing the need for extensive lymphadenectomy [45]. It is commonly used to stage breast cancer and melanoma [64]. The procedure begins with imaging of the SLN using radiotracers, such as a Tc99m-labeled sulfur colloid or Tc99m tilmanocept. The SLN is then localized with imaging and marked for surgery. Blue dye (Methylene blue, Isosulfan blue, Evans blue, or Patent blue) is then injected at the SLN, allowing for visualization of blue lymph nodes [45,65]. The nodes of interest are then excised. The biopsy procedure usually requires a small incision at the lymph node basin, followed by an excision. The extracted SLN can undergo sectioning, staining, and reverse transcriptase polymerase chain reaction (RT-PCR). Immunohistochemistry staining allows for the identification of tumors using specific proteins, such as MART-1 in melanoma. RT-PCR allows for the identification of clinical markers based on genes that are overexpressed [64]. While the lymph node often presents with tumor cells, SLN biopsy often has a false negative rate where the patient is node positive but the SLN biopsy report is negative. The false negative rate for melanoma is 10.8% [66]. The false negative rates for breast cancer were 7.0% overall, with a lower false negative rate when the radioactive tracer was combined with dye [67]. For prostate cancer, false negative rates had a median of 4.6% [68]. SLN biopsy allows for the diagnosis and staging of multiple cancers and is a very useful method to characterize and treat cancer. Furthermore, recent advancements in diagnostic techniques have significantly improved the precision of detecting lymphatic metastasis, with nanotechnology playing a pivotal role. Nanoparticles enhance imaging modalities, such as MRI, CT, and PET, by selectively targeting metastatic lymph nodes through specific biomarkers, thereby increasing sensitivity and reducing the need for invasive procedures like extensive lymphadenectomy [69].

3.3. Biomarkers for Lymphatic Spread

A variety of molecular and genetic markers characterize lymphatic spread and help identify cancer metastasis. Lymphangiogenesis markers include MMPs, VEGF, fibroblast growth factor (FGF), and platelet-derived growth factors (PDGF) (

Table 3. Predominant biomarkers involved in lymphangiogenesis and their roles in lymphatic metastasis.

Biomarkers for Lymphangiogenesis
Name	Function	Role in Metastasis
Matrix metalloproteinases	Endopeptidases	Promote angiogenesis Degrade extracellular matrix
Vascular endothelial growth factor	Signal protein	Stimulates the formation of blood vessels
Fibroblast growth factor	Signal protein	Cell proliferation Stimulates growth of new blood vessels
Platelet-derived growth factor	Signal protein	Mitogen Activates endothelial cells during angiogenesis
Lymphatic vessel endothelial hyaluronan receptor 1	Protein	Binds to hyaluronic acid Found on the surface of lymphatic endothelial cells
Podoplanin	Transmembrane glycoprotein	Associated with tumor mobility and metastasis
PROX1	Transmembrane protein	Transforms blood vessels into lymphatic vessels

). MMPs, specifically MMP9, are collagenases implicated in breast cancer metastasis due to their role in extracellular matrix degradation [70,71]. VEGF plays a key role in the regulation of lymphangiogenesis. FGF and PDGF also promote the growth and stability of lymphatic vessels. Many signaling pathways and interleukins have also been found to be associated with this pathway. The angiopoietin 2 (Ang2)/Tie/PI3K signaling pathway is essential for VEGFR-3 expression on cell surfaces [72,73,74,75]. IL-6 activates the JAK-STAT3-VEGF-C pathway, mediating VEGF-C production and, thus, lymphangiogenesis [76,77,78,79]. IL-7 has also been shown to promote lymphatic vessel development by upregulating VEGF-D [80,81,82].

Lymphatic endothelial markers have also been used to detect lymphatic spread, including the lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) gene, podoplanin, and Prospero homeobox 1 (PROX1). LYVE-1 binds with hyaluronic acid on the luminal surface of lymphatic vessels. More importantly, it is not found in blood vessels, allowing for the distinction of lymphatic vessels. Podoplanin is a transmembrane glycoprotein expressed by lymphatic endothelial cells but not vascular endothelial cells. It is also commonly utilized as a specific marker and associated with tumor spreading, inflammation, and metastasis [83]. PROX1 is a key regulator of lymphangiogenesis and also a transmembrane protein expressed on lymphatic endothelial cells. PROX1 is suggested to cause the transformation of vascular endothelium to lymphatic vessels [21]. In addition to these biomarkers, gene expression profile tests can also be performed to analyze chemotaxis, metastasis, adhesion factors, proliferation, and more. This helps identify patients who are at high risk for having a positive SLN [84]. Biomarkers for cancer can help characterize the cancer and develop a prognosis and personalized treatment response for the patient.

4. Therapeutic Strategies Targeting Lymphatic Metastasis

4.1. Surgical Approaches

Surgical strategies are fundamental in the management of lymphatic metastasis, with lymphadenectomy and sentinel lymph node dissection (SLND) being pivotal techniques employed for diagnosis, staging, and treatment. Lymphadenectomy involves the removal of lymph nodes to assess and prevent further metastatic spread of cancer. Traditionally, complete lymph node dissection has been utilized for various cancers, such as melanoma and breast cancer, to mitigate the risk of cancer progression by excising affected and potentially affected nodes. However, extensive lymphadenectomy can lead to significant complications, including lymphedema, pain, and impaired mobility, thus warranting a more selective approach [85].

SLND has emerged as a less invasive and more targeted surgical option. This procedure focuses on identifying and removing the first lymph node(s), or the sentinel nodes, to which cancer cells are most likely to spread from the primary tumor. By examining the sentinel node for metastatic cells, surgeons can determine the extent of cancer spread without resorting to complete lymphadenectomy in all cases. This approach reduces morbidity while providing crucial staging information, particularly in cancers like breast cancer and melanoma. The use of SLND has been shown to decrease unnecessary extensive node removal in patients without sentinel node involvement, thereby reducing surgical complications while maintaining accurate diagnostic capabilities [86].

While surgical approaches remain critical in the management of lymphatic metastasis, the decision to proceed with lymphadenectomy or SLND depends on factors like tumor type, stage, and individual patient characteristics, emphasizing the importance of personalized treatment strategies to balance therapeutic benefit and quality of life.

4.2. Pharmacological Inhibition of Lymphangiogenesis

Targeting lymphangiogenesis pharmacologically has emerged as a promising strategy to impede cancer progression, with multiple classes of inhibitors demonstrating efficacy in this area. One major avenue of pharmacological intervention focuses on the inhibition of VEGF signaling [87,88]. Therapeutic agents, such as bevacizumab, an anti-VEGF-A monoclonal antibody, indirectly inhibit lymphangiogenesis and have shown potential to suppress tumor-associated lymphatic expansion by disrupting VEGF pathways [89]. Other inhibitors targeting VEGF-C and VEGF-D are being explored more directly and have demonstrated efficacy in preclinical models by limiting the lymphatic spread of tumors [90,91].

Beyond VEGF-targeted therapies, tyrosine kinase inhibitors (TKIs) offer another effective approach to inhibiting lymphangiogenesis. These inhibitors, including sorafenib, sunitinib, and pazopanib, interfere with receptor tyrosine kinases, such as VEGFR-3, thereby blocking key signaling cascades essential for lymphatic vessel development and tumor cell migration [90,92,93]. By targeting multiple pathways involved in both angiogenesis and lymphangiogenesis, TKIs have demonstrated efficacy in reducing cancer dissemination through the lymphatic system, although challenges, such as resistance development and off-target toxicities, persist [94].

Furthermore, the HGF/c-Met pathway plays a critical role in lymphatic remodeling and tumor metastasis, as HGF and its receptor c-Met drive tumor cell migration and lymphangiogenesis. Therapeutic inhibitors targeting this pathway, such as monoclonal antibodies and small-molecule inhibitors, have shown preclinical success in reducing lymphatic metastases by disrupting HGF-c-Met signaling, thereby impairing new lymphatic vessel formation and tumor invasion. Similarly, MMPs facilitate extracellular matrix remodeling, which is essential for lymphatic vessel development and metastatic spread. MMP inhibitors have demonstrated efficacy in preclinical studies, reducing tumor progression and stabilizing the lymphatic microenvironment when combined with VEGF inhibitors. However, challenges, such as off-target effects and drug toxicity, highlight the need for more selective and safer therapeutic agents [87].

Other promising pharmacological agents include inhibitors targeting PDGF and fibroblast FGF, both of which have been implicated in lymphangiogenesis and tumor progression. Agents like nintedanib, which target multiple receptor tyrosine kinases, including PDGF and FGF receptors, offer broader inhibition of signaling pathways relevant to lymphatic metastasis [95]. Moreover, compounds targeting lymphangiogenic-specific markers, such as podoplanin and angiopoietin-2, are under investigation and may provide more selective therapeutic options [8].

Despite these advances, the clinical application of pharmacological inhibitors faces hurdles, including the emergence of drug resistance, off-target effects, and adverse toxicity profiles. Future research aims to optimize the use of these agents through combination therapies, improved patient stratification, and the development of next-generation inhibitors with enhanced specificity and reduced side effects. Continued exploration of novel targets within the lymphangiogenic signaling network holds the promise of more effective interventions against lymphatic metastases.

4.3. Immunotherapy and Targeted Therapies

Immunotherapy and targeted therapies have become crucial strategies in the management of lymphatic metastasis by enhancing the immune system’s ability to detect and destroy tumor cells and by inhibiting key molecular pathways that drive cancer progression. For instance, PD-1/PD-L1 inhibitors block the interaction between PD-1 on T cells and PD-L1 on tumor cells, leading to enhanced antitumor immunity and improved targeting of metastatic cells within lymph nodes [96]. Despite their success, response variability among patients remains a challenge, underscoring the need for predictive biomarkers and combination strategies to enhance efficacy [97].

In addition to immune checkpoint blockade, targeted therapies that focus on tumor-associated antigens (TAAs) and components of the tumor microenvironment (TME) have proven effective in limiting lymphatic metastasis. Monoclonal antibodies, such as trastuzumab for HER2-positive breast cancer and EGFR inhibitors for lung cancer, directly inhibit signaling pathways critical to tumor cell survival and proliferation, thereby reducing the likelihood of lymphatic spread [98]. Modulating the TME is another key focus, as it plays a significant role in promoting immune suppression and tumor survival. For instance, therapies targeting tumor-associated macrophages (TAMs) aim to transform the TME from an immunosuppressive to an immune-activated state, enhancing the body’s ability to eliminate cancer cells within lymphatic tissues [99].

Combining immunotherapy with other targeted approaches, such as anti-angiogenic agents, has also demonstrated promise in improving patient outcomes. By normalizing lymphatic vessel structure and reducing tumor-associated lymphangiogenesis, these therapies facilitate greater immune cell infiltration and restore immune function [100]. Such combination therapies seek to address resistance mechanisms and variability in patient response, aiming to provide a more robust antitumor effect and improve the overall management of lymphatic metastasis.

While these therapeutic strategies have shown great potential, challenges remain, including the emergence of resistance, patient heterogeneity, and immune-related adverse effects. Continued advancements in optimizing therapy combinations, identifying reliable biomarkers, and personalizing treatment approaches are vital to enhancing outcomes for patients with lymphatic metastasis.

4.4. Emerging Therapies and Clinical Trials

The ongoing pursuit of novel therapies for lymphatic metastasis is marked by a focus on innovative approaches that extend beyond traditional treatments, targeting unique aspects of tumor biology, immune modulation, and lymphatic-specific pathways. Recent clinical trials and emerging therapies aim to address limitations in current treatments by enhancing efficacy, overcoming resistance, and minimizing adverse effects.

Nanoparticles can deliver VEGFR-3 inhibitors and immune checkpoint inhibitors directly to lymphatic tissues, reducing systemic toxicity while improving drug efficacy. These “theranostic” platforms simultaneously offer diagnostic imaging and therapeutic capabilities, enabling real-time monitoring of treatment responses. Additionally, combining nanomedicine with immune checkpoint inhibitors or lymphangiogenesis-targeted therapies, such as VEGFR-3 inhibitors, has shown promise in clinical trials by enhancing immune cell infiltration and reducing tumor spread within the lymphatic microenvironment [101,102,103].

A key area of interest is the development of next-generation immune checkpoint inhibitors targeting pathways beyond PD-1 and PD-L1. Inhibitors of lymphocyte activation gene-3 (LAG-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT), and T cell immunoglobulin and mucin-domain containing-3 (TIM-3) are undergoing clinical evaluation, with early data suggesting the potential to enhance antitumor immunity when used alone or in combination with established checkpoint inhibitors [104,105]. By targeting alternative checkpoint pathways, these therapies seek to overcome resistance mechanisms observed in the PD-1/PD-L1 blockade, broadening the pool of patients who may benefit from immunotherapy [106,107,108,109,110,111,112,113].

Adoptive cell therapies (ACT), including chimeric antigen receptor (CAR) T-cell therapy, represent another promising avenue for lymphatic metastasis management. While primarily explored in hematologic malignancies, CAR-T cells engineered to target tumor-associated antigens are being adapted for solid tumors with lymphatic involvement. Preclinical and early-phase clinical trials are exploring the efficacy and safety of CAR-T cells directed at antigens like HER2, mesothelin, and EGFR in solid tumors, with an emphasis on optimizing their trafficking, persistence, and activity within the lymphatic microenvironment [114]. Combining CAR-T therapy with strategies to modulate the tumor microenvironment (TME), such as reducing immunosuppressive cytokines or targeting regulatory immune cells, holds the potential to enhance therapeutic outcomes.

Therapies targeting the lymphatic vasculature and lymphangiogenesis are also being investigated to disrupt the metastatic cascade. Novel agents targeting VEGFR-3 and other lymphangiogenic factors, including ANGPT2 and PROX1, aim to prevent tumor cells from entering and spreading through lymphatic vessels [88,115]. These therapies may be particularly valuable when used in combination with immune checkpoint inhibitors or traditional therapies to achieve a synergistic effect on metastasis suppression.

Epigenetic therapies targeting histone modifications and DNA methylation are also emerging as potential strategies for altering tumor cell behavior within lymphatic tissues. Modifying the expression of genes involved in immune evasion, metastasis, and lymphatic adaptation may enhance the effectiveness of existing therapies and reduce tumor resilience in the lymphatic microenvironment [116]. Clinical trials are underway to evaluate the combination of epigenetic modulators with immunotherapies and targeted therapies, aiming to overcome resistance and enhance antitumor activity.

Finally, therapeutic cancer vaccines and oncolytic viruses represent another area of intense investigation. Cancer vaccines designed to induce an immune response against tumor-associated antigens have shown promise in priming the immune system to recognize and eliminate metastatic cells within lymph nodes. Oncolytic viruses, engineered to selectively infect and lyse cancer cells, can trigger immune responses and release tumor antigens, enhancing immune system activation and potentially improving the efficacy of immunotherapies [117]. Early-phase trials exploring combinations of these modalities with checkpoint inhibitors and targeted therapies are ongoing, with the goal of amplifying antitumor immunity and reducing metastatic spread (

Table 4. Current clinical trials on drugs and solutions for the treatment of lymphatic metastasis. Source: adapted from ClinicalTrials.gov [118].

Clinical Trial	ID	Types of Cancer	Treatment Type	Status	Phase
“Radiotherapy With or Without Concurrent Chemotherapy for Limited Lymphatic Metastasis of Esophageal Cancer—3JECROG P-02”	NCT03308552	Esophageal	Radiation therapy, Paclitaxel, platinum-based drugs	Unknown	3
“Radiotherapy With or Without Concurrent Chemotherapy for Extensive Lymphatic Metastasis of Esophageal Cancer—3JECROG P-03”	NCT03328234	Esophageal	Radiation therapy, Paclitaxel, platinum-based drugs, involved field irradiation	Unknown	3
“Study of Neo-adjuvant Use of Vemurafenib Plus Cobimetinib for BRAF Mutant Melanoma with Palpable Lymph Node Metastases”	NCT02036086	Melanoma	Vemurafenib, Cobimetinib	Unknown	2
“RP1 in Primary Melanoma to Reduce the Risk of Sentinel Lymph Node Metastasis”	NCT06216938	Melanoma	Vusolimogene oderparepvec (RP1)	Recruiting	1
“Interferon Alfa-2b in Treating Patients with Melanoma and Early Lymph Node Metastasis”	NCT00004196	Melanoma	Recombinant interferon alfa	Completed	3
“Clinical Trial Comparing Carnoy’s and GEWF Solutions”	NCT02704988	Colorectal	Carnou procedure, GEWF procedure	Completed	N/A
“Targeted Resection of Axillary Metastatic Lymph Nodes After Breast Cancer Neoadjuvant Chemotherapy”	NCT04744506	Breast	Carbon Nanoparticle Suspension Injection	Recruiting	N/A
“Trial of Xeloda and Oxaliplatin (XELOX) as Neo-adjuvant Chemotherapy Followed by Surgery in Advanced Gastric Cancer Patients with Para-aortic Lymph Node Metastasis”	NCT02071043	Gastric	Capecitabine, Oxaliplatin	Completed	2
“Relation Between Tumor-draining Lymph Nodes Metastasis Pattern and Non-small Cell Lung Cancer Neoadjuvant Immunotherapy Effectiveness”	NCT06292052	Lung	Immunotherapy	Completed	N/A
“Chemo-radio-immunotherapy With Nivolumab and Ipilimumab Treatment in Locally Advanced Cervical Cancer Patients (CERAD-IMMUNE)”	NCT05504642	Cervical	Nivolumab/Ipilimumab	Withdrawn	2
“Antiandrogen Therapy with or Without Axitinib Before Surgery in Treating Patients With Previously Untreated Prostate Cancer With Known or Suspected Lymph Node Metastasis”	NCT01409200	Prostate	Antiandrogen Therapy, Axitinib	Active	2
“Safety and Efficacy of Sintilimab in Combination with Chemoradiothrapy Followed by D2 Surgical Resection in Patients With Advanced Gastric Cancer With Retroperitoneal Lymph Node Metastasis”	NCT05002686	Gastric	Sintilimab, Albumin–Paclitaxel, Capecitabine, Oxaliplatin	Unknown	2/3
“Oral Iohexol in the Management of Chylous Ascites After After Retroperitoneal or Extended Lymphadenectomy”	NCT06820320	Abdominal or pelvic tumors	Oral Iohexol	Not yet recruiting	2
“A Prospective, Multicenter Randomized Controlled Study of the Application of Preoperative FOLFOXIRI Chemotherapy Combined with Lateral Lymph Node Dissection in Low- and Medium-lying Rectal Cancer With Lateral Lymph Node Metastasis”	NCT06048146	Rectal	FOLFOXIRI (Irinotecan, Oxaliplatin), lymph node dissection	Enrolling by invitation	N/A

N/A: Not Applicable or Available.

).

5. Challenges and Future Directions in Research

One of the main challenges to cancer therapy is drug resistance, limiting the options for cancer treatment. Many patients present with resistance to immune checkpoint inhibitors due to intrinsic resistance or secondary to disease progression [119]. In addition, ATP-binding cassette transporters allow tumor cells to efflux toxic agents into the extracellular space. This is seen in breast-cancer-resistant protein ABCG2, for example. Aldehyde dehydrogenase has also been implicated in providing tumor resistance by providing resistance against alkylating agents [120].

Drug toxicity is also a serious complication of and challenge to cancer therapy. Therapy requires the use of multiple drugs to treat the malignancy, but, as a result, it can cause harmful effects. Doxorubicin and 5-Fluorouracil have been recognized to cause cardiotoxicity, which is further exacerbated by radiation therapy [121,122,123,124,125,126]. These symptoms include arrhythmias, angina, and even myocardial infarction. Bleomycin, tyrosine kinase inhibitors, and immune checkpoint inhibitors have all been found to cause pulmonary toxicity, causing interstitial pneumonitis, which can transform into pulmonary fibrosis [127,128,129,130,131]. Renal toxicity and kidney injury are also a very common side effect of chemotherapy treatment [132,133]. Cisplatin has been found to cause tubular damage, interstitial inflammation, vascular injury, hypomagnesemia, thrombotic microangiopathy, and acute kidney injury [134,135,136]. These effects can be reduced with hydration or diuresis [137]. Gastrointestinal toxicity is caused by a large number of drugs and can impart a range of symptoms, such as diarrhea, mucositis, nausea and vomiting, and xerostomia [138,139,140]. Doxorubicin, cyclophosphamide, 5-fluorouracil, and aromatase inhibitors have also been correlated with cognitive dysfunction [141,142].

CAR-T therapies also showcase both limitations and toxicities. While specific antigen binding domains are created, cancer cells often employ antigen escape, which changes the way they display antigens, making CAR-T therapy less effective. Relapsed and refractory patients generally exhibit this resistance mechanism. Tumors can either downregulate the antigen on its surface or remove the expression altogether, posing a difficult challenge to therapy. CAR-T therapy has been shown to be effective for leukemias and lymphomas, but it is ineffective at infiltrating solid tumors. Solid tumors utilize physical barriers, such as the stroma, and create an immunosuppressive environment, making CAR-T therapy difficult [143]. CAR-T therapies can cause large cytokine production due to T cell activation, resulting in a cytokine release storm. This is found in patients with acute lymphoblastic leukemia, where 23–46% experienced symptoms of high cytokine production [144]. These can include fatigue, diarrhea, headaches, arthralgia, myalgia, and potentially severe symptoms causing organ system failure. A detrimental complication includes immune effector cell-associated neurotoxicity syndrome, disrupting the blood–brain barrier [143].

Combination therapies have proven to be a means to reduce drug resistance. Multiple new combination therapies are being investigated to ensure a more enhanced response. Studies have analyzed the combination of PD-1 inhibitors (pembrolizumab) and Indoleamine-2,3-dioxygenase (IDO) inhibitors (epacadostat), which was well-tolerated but did not show much clinical benefit over PD-1 inhibitor monotherapy [145]. These drugs have also been used as a vaccine in combination with anti-PD-1 drugs [146]. Another combination therapy being explored is the anti-lymphocyte activation gene-3 (anti–LAG–3) with nivolumab, a PD-1 inhibitor. It is safe and efficacious in patients with melanoma [104]. Nivolumab has also been used in combination with Bempegaldesleukin, an IL-2 prodrug. The combination drug showed a decreased objective response of progression-free survival and an increased number of adverse events [147]. Another new therapeutic approach is restrictive combinations of drugs that take advantage of slight differences between tumors and normal cells to affect tumor cells preferentially [148]. While new combination therapies show great potential, more work needs to be done to find one that ensures high efficacy.

Personalized medicine takes each patient’s specific tumor environment into account and tailors the therapy to each individual, eliciting an improved response. Personalized therapeutic cancer vaccines provide resistance to individual tumor neoantigens. This is achieved by RNA sequencing tumor tissue and identifying relevant mutations as the target antigen for the vaccine. This allows for a tumor-specific response and elucidates a robust T-cell response [149]. Similarly, 3D culture and patient-derived xenograft models have been created to reproduce tumor characteristics, predict drug response, and implement personalized medicine [150]. These models help stimulate the heterogeneity of the tumor environment and the variety of cancer cells present. This has been used for modeling brain cancer, skin cancers, colorectal cancers, cervical cancers, lung cancers, and more [151]. These highly promising approaches emphasize the need for greater research on personalized medicine.

6. Limitations

This review is not without limitations. While it is a good introduction to the role of the lymphatic system on tumor metastasis, it remains a narrative review. We did not develop a methodological search strategy or have inclusion or exclusion criteria for the resources used in this review. Because this review serves as an overview of lymphatic metastasis, it is unable to capture the full details of the mechanism of lymphangiogenesis, diagnostic approaches, or treatments.

7. Conclusions

The lymphatic system plays a crucial role in the spread of malignant cells from the primary tumor. Tumor migration into the lymphatic system is primarily facilitated through lymphangiogenesis, characterized by the expression of MMPs, VEGF, FGF, and PDGF. Additionally, adhesion molecules and cytokines assist with the migration of the tumor cell, including CCR7, CCL21, MMPs, and VCAM-1 [70,71]. Furthermore, expression of Treg and immune checkpoint inhibitors enable tumor survival [98,103,107]. Thus, lymphatic metastasis and lymphatic invasion have proved to be significant prognostic factors determining survival and tumor progression. This is often measured using the lymph node ratio and by identifying lymphatic vessel invasion [46,48,50,55]. Lymphatic metastasis can be detected through lymphoscintigraphy and sentinel lymph node biopsy, an alternative and more targeted approach to traditional lymphadenectomy [56,58,68,86]. Management of lymphatic metastasis consists of immunotherapy using PD-1 inhibitors, monoclonal antibodies, and modulation of the tumor microenvironment [73,109,146]. These therapies have been widely successful, but challenges, such as drug resistance, adverse effects, and patient heterogeneity, still remain [128,134,141]. Emerging therapies, such as cancer vaccines, epigenetics, and CAR-T cells, represent promising solutions and emphasize the need for personalized and longitudinal medicine [27,116,117,143,149]. In conclusion, identifying new long-term therapeutic options with fewer adverse effects and reduced occurrences of resistance is crucial for patient care and disease-free survival.