Genetic Profiling of Sebaceous Carcinoma Arising from an Ovarian Mature Teratoma: A Case Report

Ovarian mature teratomas (OMTs) originate from post-meiotic germ cells. Malignant transformation occurs in approximately 1–2% of OMTs; however, sebaceous carcinoma arising from OMTs is rare. This is the first report of a detailed genomic analysis of sebaceous carcinoma arising from an OMT. A 36-year-old woman underwent evaluation for abdominal tumors and subsequent hysterectomy and salpingo-oophorectomy. Pathologically, a diagnosis of stage IA sebaceous carcinoma arising from an OMT was established. Eight months post-surgery, the patient was alive without recurrence. Immunohistochemically, the tumor was negative for mismatch repair proteins. A nonsense mutation in TP53 (p.R306*) and a deletion in PIK3R1 were identified. Single nucleotide polymorphisms across all chromosomes displayed a high degree of homozygosity, suggestive of uniparental disomy. Herein, the OMT resulting from the endoreduplication of oocytes underwent a malignant transformation to sebaceous carcinoma via TP53 as an early event and PIK3R1 as a late event.


Case Presentation
A 36-year-old woman (gravida 1, para 1) was referred to our hospital for an evaluation of abdominal tumors.Subsequently, she became pregnant.At the age of 27, she simultaneously underwent a right oophorectomy for an OMT and a cesarean section.She had no other relevant medical or family history.Her primary complaint was persistent abdominal swelling for 1 month.Systemic enhanced computed tomography and T2-weighted images from pelvic enhanced magnetic resonance imaging showed a 167 × 112 × 110 mm mass occupying the pelvic cavity, with suspected omental disseminations (Figure 1A).The preoperative diagnosis was stage IIIC left ovarian immature teratoma (cT3c cN0 M0).An intraoperative pathological diagnosis of sebaceous carcinoma was performed using frozen sections.The patient underwent total abdominal hysterectomy, left salpingo-oophorectomy, right salpingectomy, subtotal omentectomy, pelvic lymphadenectomy, and para-aortic lymphadenectomy.Complete resection was achieved.Macroscopically, the right ovarian tumor appeared as a well-circumscribed, yellowish-white mass with hair and partial necrosis (Figure 1B).Microscopically, the tumor exhibited sheets or lobules separated by a fibrovascular stroma of basophilic and atypical cells with central comedo-type necrosis (Figure 1C,D).

Case Presentation
A 36-year-old woman (gravida 1, para 1) was referred to our hospital for an evaluation of abdominal tumors.Subsequently, she became pregnant.At the age of 27, she simultaneously underwent a right oophorectomy for an OMT and a cesarean section.She had no other relevant medical or family history.Her primary complaint was persistent abdominal swelling for 1 month.Systemic enhanced computed tomography and T2weighted images from pelvic enhanced magnetic resonance imaging showed a 167 × 112 × 110 mm mass occupying the pelvic cavity, with suspected omental disseminations (Figure 1A).The preoperative diagnosis was stage IIIC left ovarian immature teratoma (cT3c cN0 M0).An intraoperative pathological diagnosis of sebaceous carcinoma was performed using frozen sections.The patient underwent total abdominal hysterectomy, left salpingo-oophorectomy, right salpingectomy, subtotal omentectomy, pelvic lymphadenectomy, and para-aortic lymphadenectomy.Complete resection was achieved.Macroscopically, the right ovarian tumor appeared as a well-circumscribed, yellowish-white mass with hair and partial necrosis (Figure 1B).Microscopically, the tumor exhibited sheets or lobules separated by a fibrovascular stroma of basophilic and atypical cells with central comedo-type necrosis (Figure 1C,D).The tumor exhibited an epidermis, hair follicles, and sebaceous glands.No dissemination to the greater omentum or lymph node metastases was observed.Immunohistochemical staining revealed tumor cells positive for androgen receptors (Figure 2A), GATAbinding protein 3, adipophilin (Figure 2B), and mismatch repair proteins MLH1 (Figure 2C), MSH2 (Figure 2D), MSH6 (Figure 2E), and PMS2 (Figure 2F).The tumor exhibited an epidermis, hair follicles, and sebaceous glands.No dissemination to the greater omentum or lymph node metastases was observed.Immunohistochemi-cal staining revealed tumor cells positive for androgen receptors (Figure 2A), GATA-binding protein 3, adipophilin (Figure 2B), and mismatch repair proteins MLH1 (Figure 2C), MSH2 (Figure 2D), MSH6 (Figure 2E), and PMS2 (Figure 2F).Accordingly, a diagnosis of stage IA (pT1a, pN0, M0) sebaceous carcinoma arising from an OMT was established.No post-operative adjuvant therapy was administered.The patient was alive without recurrence 8 months post-operation.
Genomic DNA was obtained from a sample classified as a sebaceous carcinoma but not an OMT-which was considered a separate precursor lesion-because of limited sample volume.Cancer gene profiling was performed using the PleSSision system as previously described [21].The average sequencing depth was 619.4× for sebaceous carcinoma.Histologically, the average tumor cellularity was 60%.In an analysis using a cancer gene panel of 160 genes in a sebaceous carcinoma sample, several actionable gene alterations were observed (Table S1).Nonsense mutation in TP53 (p.R306*) and deletions in PIK3R1, Accordingly, a diagnosis of stage IA (pT1a, pN0, M0) sebaceous carcinoma arising from an OMT was established.No post-operative adjuvant therapy was administered.The patient was alive without recurrence 8 months post-operation.
Genomic DNA was obtained from a sample classified as a sebaceous carcinoma but not an OMT-which was considered a separate precursor lesion-because of limited sample volume.Cancer gene profiling was performed using the PleSSision system as previously described [21].The average sequencing depth was 619.4× for sebaceous carcinoma.His-tologically, the average tumor cellularity was 60%.In an analysis using a cancer gene panel of 160 genes in a sebaceous carcinoma sample, several actionable gene alterations were observed (Table S1).Nonsense mutation in TP53 (p.R306*) and deletions in PIK3R1, ATRX, and APC were identified.In summary, a DNA quality check using the Agilent 2000 TapeStation (Agilent Technologies, Santa Clara, CA, USA), targeted amplicon exome sequencing using the Illumina MiSeq sequencing platform (Illumina, San Diego, CA, USA), and sequencing data analysis using the GenomeJack bioinformatics pipeline (version 1.0,Mitsubishi Space Software, Tokyo, Japan) were performed.The copy number loss/amplification cutoff was set to 1.1/3.6,which is statistically > 2σ.Single nucleotide polymorphisms across all chromosomes displayed a high degree of homozygosity, with allelic frequencies near 100% in nearly all of the genes examined (Figure 3 and Table S2).This pervasive pattern was evident across the entire genome.The tumor was characterized as microsatellite stable, and the tumor mutation burden was measured at 5.5 single nucleotide variants per megabase.nt.J. Mol.Sci.2024, 25, x FOR PEER REVIEW 4 of 8 loss/amplification cutoff was set to 1.1/3.6,which is statistically > 2σ.Single nucleotide polymorphisms across all chromosomes displayed a high degree of homozygosity, with allelic frequencies near 100% in nearly all of the genes examined (Figure 3 and Table S2) This pervasive pattern was evident across the entire genome.The tumor was characterized as microsatellite stable, and the tumor mutation burden was measured at 5.5 single nucle otide variants per megabase.

Discussion
To the best of our knowledge, this is the first report of a detailed genomic analysis o sebaceous carcinoma arising from an OMT.The 14 previously reported cases are summa rized in Table 1 [8-20].In the four reports that investigated mismatch repair abnormality protein/gene abnormality was identified in all four cases [8, 9,11,14].However, since this case did not exhibit mismatch repair/gene abnormality and microsatellite instability, al

Discussion
To the best of our knowledge, this is the first report of a detailed genomic analysis of sebaceous carcinoma arising from an OMT.The 14 previously reported cases are summa-rized in .In the four reports that investigated mismatch repair abnormality, protein/gene abnormality was identified in all four cases [8, 9,11,14].However, since this case did not exhibit mismatch repair/gene abnormality and microsatellite instability, alternate pathogeneses had to be considered.Nonsense mutation of TP53 (p.R306*) and a deletion in PIK3R1 were detected in the targeted next-generation sequencing.Cooke et al. [22] reported that the most frequently altered genes were TP53 (80%), PIK3CA (52%), and CDKN2A (44%), and that TP53 mutation is an early event in squamous cell carcinoma arising from OMTs.Strikingly, 40% of the TP53 mutations were biallelic, which may be associated with improved outcomes [22].KRAS amplification and a deletion of PTEN and RB1 were detected in malignant melanoma arising from OMT [21].No previous studies have reported cases of OMT or sebaceous carcinoma with PIK3R1 mutations.Rubinstein et al. [23] reported the safety and efficacy of the dual PI3K/mTOR inhibitor in patients with advanced endometrial cancer and activating mutations in the PI3K pathway, including PIK3R1.Single nucleotide polymorphisms across all chromosomes displayed a high degree of homozygosity, except PIK3R1A.PIK3R1 mutations had a relatively low VAF because they were present in some, but not all, tumors.This PIK3R1 mutation is considered a late event that occurs in a subclone after the malignant transformation of an OMT.The observed extensive homozygosity and the uniform allelic frequencies close to 100% suggest the presence of UPD across all chromosomes.Such widespread UPD is unusual and highlights a significant alteration from the expected heterozygous genetic landscape typical of diploid cells.The implications of this finding are profound, as UPD can lead to disruptions in gene expression, loss of heterozygosity, and potential impacts on tumor suppressor genes and oncogenes.This genetic uniformity may contribute to the oncogenic process by altering the cellular landscape, potentially leading to an enhanced tumorigenic capacity.The mechanisms driving such extensive UPD and its role in the progression of the tumor warrant further investigation to understand its contribution to cancer biology and therapy.
OMTs are classified into five types (I-V) based on their cytogenetic features [24].Type I OMTs result from errors in meiosis I, type II OMTs result from meiosis II failure, type III OMTs occur via endoreduplication of a haploid ovum, type IV arises from oogonia, and type V OMTs are considered to originate from the fusion of two normal haploid ovaries [1,2,24].Notably, the sebaceous carcinoma lacked heterozygous pleomorphism in the whole genome, suggesting that the sebaceous carcinoma arose from a type III OMT via endoreduplication of a haploid ovum [1,2].Using short tandem repeat polymorphism analysis of centromeric and distal markers, Usui et al. reported that all OMTs were of post-meiotic origin rather than of pre-meiotic origin.Finally, the developmental process of this tumor is explained as follows.Type III OMTs resulted from the endoreduplication of oocytes after meioses I and II.As an early event, a TP53 mutation occurred, leading to the development of sebaceous gland carcinoma.Subsequently, a subclone acquired a PIK3R1 mutation as a late event.However, the present study is a case report, and future case studies are required to confirm the reproducibility of our findings.In conclusion, an OMT resulting from the endoreduplication of oocytes underwent malignant transformation to sebaceous carcinoma via TP53 as an early event and PIK3R1 as a late event in the present case.These mutations may also be useful for prognosis prediction and targeted therapy.Genetic analysis is important to elucidate the pathogenesis of this rare tumor, and further case collection is required.

Figure 1 .
Figure 1.(A) MRI image findings: A 167 × 112 × 110 mm mass extending from the midline of the pelvis to the left with dissemination into the large omentum.(B) Macroscopic findings: solid proliferation mainly composed of fat components.(C,D) Histological findings (H&E staining): (C, x10) proliferation of tumor cells with differentiation potential into sebaceous glands cells on the background of hairs, (D, x40) proliferation of basophilic and mildly atypical cells with mitotic figure on the background of fibrosis and necrosis.

Figure 1 .
Figure 1.(A) MRI image findings: A 167 × 112 × 110 mm mass extending from the midline of the pelvis to the left with dissemination into the large omentum.(B) Macroscopic findings: solid proliferation mainly composed of fat components.(C,D) Histological findings (H&E staining): (C, ×10) proliferation of tumor cells with differentiation potential into sebaceous glands cells on the background of hairs, (D, ×40) proliferation of basophilic and mildly atypical cells with mitotic figure on the background of fibrosis and necrosis.