The Neoplastic Side of the Abdominal Wall: A Comprehensive Pictorial Essay of Benign and Malignant Neoplasms

Abdominal wall neoplasms are usually benign and, in the majority of these cases, no further work-up or treatment is indicated. The percentage of malignant abdominal neoplasms, however, is not negligible. Radiologists play a pivotal role in identifying imaging features that should favor malignancy, including larger lesion size, edema, neurovascular involvement, and peripheral or inhomogeneous dynamic enhancement, thus indicating to the clinician the need for further work-up. Histopathology is the reference standard for the characterization of abdominal wall neoplasms. In patients undergoing surgery, radiological assessment is needed to guide the surgeon by providing a comprehensive anatomic guide of the tumor extension. We present a pictorial review of benign and malignant abdominal wall neoplasms that can be encountered on radiological examinations, with a main focus on CT and MRI features that help in narrowing the differential diagnosis.


Introduction
Abdominal wall neoplasms may be encountered incidentally on imaging or may present as palpable masses, leading the patient to the radiologist. Malignancies could be identified in about 40% of cases, based on a study by Bashir et al. [1]. However, this percentage is likely overestimated, as this study was based on a population of 365 patients referred to a sarcoma clinic; therefore, the percentage in the overall population is very likely to be much lower. Hence, in most cases, abdominal wall neoplasms have a benign nature and do not require further work-up or treatment.
Radiologists play a pivotal role in recognizing imaging features that deserve close attention. Imaging features that should favor malignancy in soft-tissue tumors of the abdominal wall include larger lesion size, edema, neurovascular involvement, and peripheral or inhomogeneous dynamic enhancement [2,3].
Ultrasonography (US) is the first-line imaging technique for abdominal wall masses, and it is indicated in patients with palpable masses in the abdominal wall. US plays a main role both for diagnosis and as a guide for interventional procedures and biopsies. In many cases, however, abdominal wall neoplasms are identified incidentally on computed tomography (CT) and magnetic resonance (MR) [1].
CT provides information on tumor extension and involvement of deeper abdominal wall structures, but it is burdened by ionizing radiation exposure. Contrast-enhanced MR is a second-line imaging technique that allows a better understanding of the composition and nature of a mass [2,3]. Histopathology, however, still remains the reference standard for final diagnosis.
Based on the European Society of Musculoskeletal Radiology (ESSR) guidelines on soft tissue tumors, masses above 5 cm should always undergo biopsy after imaging [3].
Malignant lesions usually show a larger volume, heterogeneous structure (mainly on MR), and heterogeneous and early contrast enhancement [5]. Around 80% of all abdominal wall malignant primary tumors fall into seven categories: myxofibrosarcoma, liposarcomas, leiomyosarcomas, malignant nerve sheath tumors, synovial cell sarcoma, fibrosarcoma, and sarcoma not otherwise specified (NOS) [4].
This pictorial review aims to provide an overview of the broad spectrum of all these benign and malignant neoplasms, with tips for the differential diagnosis. For each condition, key imaging aspects will be highlighted, in order to provide a complete visual diagnostic guide for the radiologist. Table 1 summarizes the main imaging features of benign neoplasms of the abdominal wall.

Lipoma
Lipoma is the most frequent benign soft tissue tumor, with a prevalence ranging from 16% to 50% [1,5,6]. Simple lipomas are homogeneous fatty masses with minimal-to-no enhancement ( Figure 1) [6][7][8][9]. Their imaging appearance will mirror that of fat and appear as homogeneous and isoechoic or hyperechoic on US; strongly hypodense on CT; and with the same MR signal intensity of subcutaneous and intrabdominal fatty tissues. Of note, Dual Echo sequences will not show signal dropout since lipomas contain extracellular fat.

Lipoma
Lipoma is the most frequent benign soft tissue tumor, with a prevalence ranging fro 16% to 50% [1,5,6]. Simple lipomas are homogeneous fatty masses with minimal-toenhancement ( Figure 1) [6][7][8][9]. Their imaging appearance will mirror that of fat and appe as homogeneous and isoechoic or hyperechoic on US; strongly hypodense on CT; a with the same MR signal intensity of subcutaneous and intrabdominal fatty tissues. note, Dual Echo sequences will not show signal dropout since lipomas contain extracel lar fat. When inflammation, necrosis, or infarction occur, a heterogeneous appearance with calcifications, thin septa (<2 mm), or bands of muscle fibers can be appreciated [7, In these cases, differentiation with liposarcoma cannot be made at imaging, and biopsy surgical resection is recommended [6], especially in bigger lesions. When solid comp nents are present, liposarcoma should always be ruled out [6,9].
Lipomas are commonly painless, have no malignant potential, and do not requ follow-up. However, subcutaneous lipomas could be surgically removed for symptoma relief, pathologic confirmation, cosmetic reasons, or if there is an increase in size [9,10]. these cases, pre-operative CT can be performed to depict their extent. Complete surgi excision including the capsule is advocated to avoid local recurrence. In painful subcu neous lipomas, either isolated or syndromic (e.g., Dercum's Disease), management cludes options such as liposuction or lidocaine applications [10].
On imaging, desmoid tumors resemble the surrounding muscles [11][12][13]. H poechoic, poorly circumscribed, with internal vascular flow on US ( Figure 2) [7,13], th are commonly briskly hyperattenuating and homogeneous on contrast-enhanced C with either circumscribed or ill-defined margins and without washout [13]. When inflammation, necrosis, or infarction occur, a heterogeneous appearance [9] with calcifications, thin septa (<2 mm), or bands of muscle fibers can be appreciated [7,8]. In these cases, differentiation with liposarcoma cannot be made at imaging, and biopsy or surgical resection is recommended [6], especially in bigger lesions. When solid components are present, liposarcoma should always be ruled out [6,9].
Lipomas are commonly painless, have no malignant potential, and do not require follow-up. However, subcutaneous lipomas could be surgically removed for symptomatic relief, pathologic confirmation, cosmetic reasons, or if there is an increase in size [9,10]. In these cases, pre-operative CT can be performed to depict their extent. Complete surgical excision including the capsule is advocated to avoid local recurrence. In painful subcutaneous lipomas, either isolated or syndromic (e.g., Dercum's Disease), management includes options such as liposuction or lidocaine applications [10].
On imaging, desmoid tumors resemble the surrounding muscles [11][12][13]. Hypoechoic, poorly circumscribed, with internal vascular flow on US ( Figure 2) [7,13], they are commonly briskly hyperattenuating and homogeneous on contrast-enhanced CT, with either circumscribed or ill-defined margins and without washout [13]. B-mode US scan shows a rounded, poorly circumscribed mass in the context of the abdominal muscles (*), heterogeneously hypoechoic, but similar to muscles that underwent biopsy (right picture).
Larger tumors may appear heterogeneous, as a result of bleeding or necrosis, and may contain calcifications [11][12][13]. On MR, desmoid tumors have low-to-intermediate T1weighted (T1-w) signal and high T2-weighted (T2-w) foci, which during subsequent follow-ups become isointense to the surrounding muscles ( Figure 3) [3,4,12]. Imaging appearance overlaps with other abdominal wall masses, so tissue sampling is required when desmoids are suspected [1]. The first sign of a desmoid tumor may be a firm, painless lump. When they develop in flexible, elastic tissues or deep spaces, the tumor can often push normal tissue out of its way as it grows, causing vague symptoms. In the past years, direct complete surgery was the standard primary treatment modality; however, in recent years a paradigm shift towards a conservative management has been introduced in order to prevent local recurrences, as they are usually more aggressive than the original tumor [14]. Moreover, recent studies showed no difference in event-free survival and long-term disease control between patients undergoing surgery and those managed with a conservative approach among patients presenting with favorable locations, such as the abdominal wall [14,15].

Hemangioma
Abdominal wall hemangiomas are rare mesenchymal tumors (<1%), mainly occurring in children [16,17]. US will demonstrate iso-or hypoechoic lesions, similar to surrounding muscles, with ill-defined borders, in the context of abdominal wall muscles [16;18], presenting feeding vessels with arterial parenchymal waveforms on color Doppler, usually with high resistive index ( Figure 4) [16][17][18]. B-mode US scan shows a rounded, poorly circumscribed mass in the context of the abdominal muscles (*), heterogeneously hypoechoic, but similar to muscles that underwent biopsy (right picture).
Larger tumors may appear heterogeneous, as a result of bleeding or necrosis, and may contain calcifications [11][12][13]. On MR, desmoid tumors have low-to-intermediate T1-weighted (T1-w) signal and high T2-weighted (T2-w) foci, which during subsequent follow-ups become isointense to the surrounding muscles ( Figure 3) [3,4,12]. Imaging appearance overlaps with other abdominal wall masses, so tissue sampling is required when desmoids are suspected [1].  B-mode US scan shows a rounded, poorly circumscribed mass in the context of the abdominal muscles (*), heterogeneously hypoechoic, but similar to muscles that underwent biopsy (right picture).
Larger tumors may appear heterogeneous, as a result of bleeding or necrosis, and may contain calcifications [11][12][13]. On MR, desmoid tumors have low-to-intermediate T1weighted (T1-w) signal and high T2-weighted (T2-w) foci, which during subsequent follow-ups become isointense to the surrounding muscles ( Figure 3) [3,4,12]. Imaging appearance overlaps with other abdominal wall masses, so tissue sampling is required when desmoids are suspected [1]. The first sign of a desmoid tumor may be a firm, painless lump. When they develop in flexible, elastic tissues or deep spaces, the tumor can often push normal tissue out of its way as it grows, causing vague symptoms. In the past years, direct complete surgery was the standard primary treatment modality; however, in recent years a paradigm shift towards a conservative management has been introduced in order to prevent local recurrences, as they are usually more aggressive than the original tumor [14]. Moreover, recent studies showed no difference in event-free survival and long-term disease control between patients undergoing surgery and those managed with a conservative approach among patients presenting with favorable locations, such as the abdominal wall [14,15].

Hemangioma
Abdominal wall hemangiomas are rare mesenchymal tumors (<1%), mainly occurring in children [16,17]. US will demonstrate iso-or hypoechoic lesions, similar to surrounding muscles, with ill-defined borders, in the context of abdominal wall muscles [16;18], presenting feeding vessels with arterial parenchymal waveforms on color Doppler, usually with high resistive index ( Figure 4) [16][17][18]. The first sign of a desmoid tumor may be a firm, painless lump. When they develop in flexible, elastic tissues or deep spaces, the tumor can often push normal tissue out of its way as it grows, causing vague symptoms. In the past years, direct complete surgery was the standard primary treatment modality; however, in recent years a paradigm shift towards a conservative management has been introduced in order to prevent local recurrences, as they are usually more aggressive than the original tumor [14]. Moreover, recent studies showed no difference in event-free survival and long-term disease control between patients undergoing surgery and those managed with a conservative approach among patients presenting with favorable locations, such as the abdominal wall [14,15].
On MR, abdominal wall hemangiomas are isointense or only slightly hyperintense on T1-w images, and hyperintense on T2-w ones [3,8,17], with low-signal spots corresponding to phleboliths, that will create the so-called "blooming artifact" on Dual Echo sequences [16]. Two clues for the diagnosis are the presence of a fat-rim in intramuscular hemangiomas (i.e., an outer loss of signal in all fat-suppressed sequences) [4] and the presence of fluid-fluid levels within the lesion, for more than two thirds of its diameter [4,19], related to slow-moving flows within the hemangioma [19].
Although true hemangiomas have no malignant potential, all management strategies should include regular follow-ups.
Conservative management is the first line of treatment for nearly all isolated intramuscular hemangiomas. When the degree of pain or functional impairment warrants more intervention, nonoperative measures may decrease symptoms, and, if On CT, hemangiomas appear as lesions without clearly infiltrating characteristics, usually with phleboliths, which are punctuate calcifications, suggestive for the diagnosis [8]. In post-contrast sequences, hemangiomas show early homogeneous enhancement or progressive centripetal enhancement [18].
On MR, abdominal wall hemangiomas are isointense or only slightly hyperintense on T1-w images, and hyperintense on T2-w ones [3,8,17], with low-signal spots corresponding to phleboliths, that will create the so-called "blooming artifact" on Dual Echo sequences [16]. Two clues for the diagnosis are the presence of a fat-rim in intramuscular hemangiomas (i.e., an outer loss of signal in all fat-suppressed sequences) [4] and the presence of fluidfluid levels within the lesion, for more than two thirds of its diameter [4,19], related to slow-moving flows within the hemangioma [19].
Although true hemangiomas have no malignant potential, all management strategies should include regular follow-ups.
Conservative management is the first line of treatment for nearly all isolated intramuscular hemangiomas. When the degree of pain or functional impairment warrants more intervention, nonoperative measures may decrease symptoms, and, if nonresponsive, options include conservative management, topical or systemic corticosteroids, embolization, sclerotherapy, and surgical excision [20].

Nerve Sheath Tumors
Benign nerve sheath tumors (NSTs) are mainly comprised of neurinomas and schwannomas and are typically located along the course of major peripheral nerves [1,7,8,13]. If multiple lesions are seen, neurofibromatosis type I (NF1) should always be ruled out, [1,3,8,13] as it is associated with a higher risk of malignant degeneration of NSTs and therefore requires periodical follow-up [3]. On US, NSTs appear as smooth well-defined lobulated masses ( Figure 5), homogenously hypoechoic on US, without intralesional vascularization, hypoattenuating on CT, with minimal-to-no enhancement.

Nerve Sheath Tumors
Benign nerve sheath tumors (NSTs) are mainly comprised of neurinomas and schwannomas and are typically located along the course of major peripheral nerves [1,7,8,13]. If multiple lesions are seen, neurofibromatosis type I (NF1) should always be ruled out, [1,3,8,13] as it is associated with a higher risk of malignant degeneration of NSTs and therefore requires periodical follow-up [3]. On US, NSTs appear as smooth well-defined lobulated masses ( Figure 5), homogenously hypoechoic on US, without intralesional vascularization, hypoattenuating on CT, with minimal-to-no enhancement. Neurofibromas and schwannomas contain a solid and a myxoid part and will show low signal on T1-w images, with heterogeneous appearance on T2-w images. A "target sign" could also be appreciated on T2-w sequences [1][2][3][4]8], consisting of a peripheral high intensity area, with central low signal, reflecting myxoid degeneration [1,13]. After gadolinium, a "reverse target sign" will appear, given that the enhancement is only central. [21] Another diagnostic tip is the presence of the "split fat sign", a rim of fat around the tumor [8]. If malignant degeneration occurs, inhomogeneous enhancement and rapid growth will appear, together with ill-defined margins, infiltration, and destructive changes in adjacent bone structures ( Figure 6). NSTs of the abdominal wall are usually asymptomatic or just slightly symptomatic and can be managed through follow-up, but are exclusively treated by excision. Prognosis is good with low recurrence rates [22]. Neurofibromas and schwannomas contain a solid and a myxoid part and will show low signal on T1-w images, with heterogeneous appearance on T2-w images. A "target sign" could also be appreciated on T2-w sequences [1][2][3][4]8], consisting of a peripheral high intensity area, with central low signal, reflecting myxoid degeneration [1,13]. After gadolinium, a "reverse target sign" will appear, given that the enhancement is only central [21]. Another diagnostic tip is the presence of the "split fat sign", a rim of fat around the tumor [8]. If malignant degeneration occurs, inhomogeneous enhancement and rapid growth will appear, together with ill-defined margins, infiltration, and destructive changes in adjacent bone structures ( Figure 6). NSTs of the abdominal wall are usually asymptomatic or just slightly symptomatic and can be managed through follow-up, but are exclusively treated by excision. Prognosis is good with low recurrence rates [22].

Sarcomas
Sarcomas are rare mesenchymal tumors, often large, with poorly defined margins, which can arise in the subcutaneous tissue or in the musculature of the abdominal wall [2,3,23]. The most common types are liposarcomas and leiomyosarcomas [3].
Sarcomas of the abdominal wall are usually non-vascularized solid masses, with necrotic or fluid areas [23], giving the lesion a heterogeneous aspect, mostly hypoechoic on US, with anechoic parts corresponding to fluid degeneration. CT will better characterize extension, staging, and the anatomic origin and will demonstrate hyperattenuating, softdensity structures, with early heterogeneous enhancement ( Figure 7)

Sarcomas
Sarcomas are rare mesenchymal tumors, often large, with poorly defined margins, which can arise in the subcutaneous tissue or in the musculature of the abdominal wall [2,3,23]. The most common types are liposarcomas and leiomyosarcomas [3].

Subcutaneous Lymphoma
Lymphoma may involve the subcutaneous tissue, muscles, and skin of the abdominal wall, as a primary process, by contiguous extension or by hematogenous and lymphatic spread [11][12][13]. The diagnosis is primarily based on diffuse or systemic lymphatic involvement and hepatosplenomegaly [33]. Findings include large masses, nodal or confluent nodal structures, small nodules (<1 cm), disseminated myositis, or panniculitis [13]. On US, subcutaneous lymphoma presents as a well-defined, hypoechoic lesion without increased vascularity [34]. On cross-sectional imaging, confluent masses with homogeneous or heterogeneous enhancement can be appreciated ( Figure 11) [13]. On MRI, abdominal wall lymphomas show high T2 signal, rarely low-to-intermediate [34], homogenous signal, lack of central necrosis in large lesions [34], lymphangitis, and the "wrapped-around" sign of lymphoma around bony structures [34].

Subcutaneous Lymphoma
Lymphoma may involve the subcutaneous tissue, muscles, and skin of the abdominal wall, as a primary process, by contiguous extension or by hematogenous and lymphatic spread [11][12][13]. The diagnosis is primarily based on diffuse or systemic lymphatic involvement and hepatosplenomegaly [33]. Findings include large masses, nodal or confluent nodal structures, small nodules (<1 cm), disseminated myositis, or panniculitis [13]. On US, subcutaneous lymphoma presents as a well-defined, hypoechoic lesion without increased vascularity [34]. On cross-sectional imaging, confluent masses with homogeneous or heterogeneous enhancement can be appreciated ( Figure 11) [13].

Subcutaneous Lymphoma
Lymphoma may involve the subcutaneous tissue, muscles, and skin of the abdominal wall, as a primary process, by contiguous extension or by hematogenous and lymphatic spread [11][12][13]. The diagnosis is primarily based on diffuse or systemic lymphatic involvement and hepatosplenomegaly [33]. Findings include large masses, nodal or confluent nodal structures, small nodules (<1 cm), disseminated myositis, or panniculitis [13]. On US, subcutaneous lymphoma presents as a well-defined, hypoechoic lesion without increased vascularity [34]. On cross-sectional imaging, confluent masses with homogeneous or heterogeneous enhancement can be appreciated ( Figure 11) [13]. On MRI, abdominal wall lymphomas show high T2 signal, rarely low-to-intermediate [34], homogenous signal, lack of central necrosis in large lesions [34], lymphangitis, and the "wrapped-around" sign of lymphoma around bony structures [34]. On MRI, abdominal wall lymphomas show high T2 signal, rarely low-to-intermediate [34], homogenous signal, lack of central necrosis in large lesions [34], lymphangitis, and the "wrapped-around" sign of lymphoma around bony structures [34].

Metastasis
Around 5-10% of all oncologic patients may develop abdominal wall metastases (AWMs) [11]. Secondary AWMs derive from hematogenous or lymphatic spread, direct invasion, or needle-tract seeding [1,13]. When the abdominal wall is the sole potential site of metastasis seen on imaging, biopsy is still recommended (Figure 12) [1].

Metastasis
Around 5-10% of all oncologic patients may develop abdominal wall metastases (AWMs) [11]. Secondary AWMs derive from hematogenous or lymphatic spread, direct invasion, or needle-tract seeding [1,13]. When the abdominal wall is the sole potential site of metastasis seen on imaging, biopsy is still recommended (Figure 12) [1]. Imaging findings are nonspecific [1][2][3] but include single or multiple soft-tissue nodules that resemble the primary lesion in both appearance and contrast behavior [1]. On CT and MR, heterogeneous or peripheral enhancement will usually be seen [13,35], an appearance called "pseudo-target sign" [4].
AWMs can also be a consequence of laparoscopy, needle biopsies, and radiofrequency ablation [37] in multiple cancers, including hepatobiliary malignancies, neuroendocrine tumors, peritoneal carcinomatosis, and gastric cancer, reaching a prevalence of 16-47% in gynecologic malignancies [35]. Imaging findings are nonspecific [1][2][3] but include single or multiple soft-tissue nodules that resemble the primary lesion in both appearance and contrast behavior [1]. On CT and MR, heterogeneous or peripheral enhancement will usually be seen [13,35], an appearance called "pseudo-target sign" [4].
Breast cancer is one of the most common causes of abdominal wall and subcutaneous metastasis, with an incidence between 5 and 24% ( Figure 13) [36].

Metastasis
Around 5-10% of all oncologic patients may develop abdominal wall metastases (AWMs) [11]. Secondary AWMs derive from hematogenous or lymphatic spread, direct invasion, or needle-tract seeding [1,13]. When the abdominal wall is the sole potential site of metastasis seen on imaging, biopsy is still recommended (Figure 12) [1]. Imaging findings are nonspecific [1][2][3] but include single or multiple soft-tissue nodules that resemble the primary lesion in both appearance and contrast behavior [1]. On CT and MR, heterogeneous or peripheral enhancement will usually be seen [13,35], an appearance called "pseudo-target sign" [4].
AWMs can also be a consequence of laparoscopy, needle biopsies, and radiofrequency ablation [37] in multiple cancers, including hepatobiliary malignancies, neuroendocrine tumors, peritoneal carcinomatosis, and gastric cancer, reaching a prevalence of 16-47% in gynecologic malignancies [35]. Melanoma metastasis are also common, and have a tendency to bleed [11,[35][36][37][38][39][40]. They are hypervascular in 10-17% of cases, with high T1 signal on MR, due to the presence of melanin. Other primary tumors that may lead to AWMs include lung cancer [39], gynecological malignancies, and colorectal cancer ( Figure 14) [40,41]. A particular AWM appearance is "Sister Mary Joseph's Nodule" (SMJN), a metastatic deposit located in the umbilicus. SMJN can be the first complaint of an unknown cancer and it is indicative of an aggressive disease [42][43][44][45][46]. The most common primary sites of SMJN are, in order of frequency, pancreato-biliary, gastrointestinal, colorectal, ovarian, and endometrial adenocarcinomas, [35,38,[43][44][45][46] even though one fourth of cases will derive from undifferentiated cancers ( Figure 15) [46]. SMJN can be the first known sign of a malignancy, as the appearance of the navel will alert the patient to seek medical attention. Figure 15. A 50-year-old woman with an umbilical mass. Axial, portal venous phase CT scan shows a collection of masses with heterogeneous, peripheral enhancement metastases along the navel (arrow). It was then demonstrated that the primary site of the tumor was an undifferentiated pancreatic carcinoma.

Conclusions
The spectrum of abdominal wall neoplasms is wide, ranging from benign tumors that can be conservatively managed to malignant ones, which require treatment. AWMs can also be a consequence of laparoscopy, needle biopsies, and radiofrequency ablation [37] in multiple cancers, including hepatobiliary malignancies, neuroendocrine tumors, peritoneal carcinomatosis, and gastric cancer, reaching a prevalence of 16-47% in gynecologic malignancies [35].
A particular AWM appearance is "Sister Mary Joseph's Nodule" (SMJN), a metastatic deposit located in the umbilicus. SMJN can be the first complaint of an unknown cancer and it is indicative of an aggressive disease [42][43][44][45][46]. The most common primary sites of SMJN are, in order of frequency, pancreato-biliary, gastrointestinal, colorectal, ovarian, and endometrial adenocarcinomas, [35,38,[43][44][45][46] even though one fourth of cases will derive from undifferentiated cancers ( Figure 15) [46]. SMJN can be the first known sign of a malignancy, as the appearance of the navel will alert the patient to seek medical attention. A particular AWM appearance is "Sister Mary Joseph's Nodule" (SMJN), a metastatic deposit located in the umbilicus. SMJN can be the first complaint of an unknown cancer and it is indicative of an aggressive disease [42][43][44][45][46]. The most common primary sites of SMJN are, in order of frequency, pancreato-biliary, gastrointestinal, colorectal, ovarian, and endometrial adenocarcinomas, [35,38,[43][44][45][46] even though one fourth of cases will derive from undifferentiated cancers ( Figure 15) [46]. SMJN can be the first known sign of a malignancy, as the appearance of the navel will alert the patient to seek medical attention. Figure 15. A 50-year-old woman with an umbilical mass. Axial, portal venous phase CT scan shows a collection of masses with heterogeneous, peripheral enhancement metastases along the navel (arrow). It was then demonstrated that the primary site of the tumor was an undifferentiated pancreatic carcinoma.

Conclusions
The spectrum of abdominal wall neoplasms is wide, ranging from benign tumors that can be conservatively managed to malignant ones, which require treatment. Figure 15. A 50-year-old woman with an umbilical mass. Axial, portal venous phase CT scan shows a collection of masses with heterogeneous, peripheral enhancement metastases along the navel (arrow). It was then demonstrated that the primary site of the tumor was an undifferentiated pancreatic carcinoma.

Conclusions
The spectrum of abdominal wall neoplasms is wide, ranging from benign tumors that can be conservatively managed to malignant ones, which require treatment.
The role of the radiologist is fundamental in curtailing the differential diagnosis and correctly interpreting these processes, especially in the case of incidental findings.
Some imaging clues may help to narrow the differential diagnosis, indicating the need for further diagnostic work-up in case of larger lesion size, edema, neurovascular involvement, or peripheral or inhomogeneous dynamic enhancement. Some benign tumors may have atypical features or may lead to complications, and this may lead to diagnostic challenges at imaging and indicate the need for a biopsy to rule out malignancy.