Mismatch repair deficiency is implicated in carcinoma arising from ovarian teratoma

Successful treatment of advanced squamous cell carcinoma arising from mature cystic teratoma of the ovary with homologous recombination deficiency: A case report

INTRODUCTION AND IMPORTANCE

Squamous cell carcinoma (SCC) arising from mature cystic teratoma of the ovary (MCT-SCC) has a poor prognosis at advanced stages. Although the relationship between homologous recombination deficiency (HRD) and platinum-based chemotherapy sensitivity or poly (ADP ribose) polymerase (PARP) inhibitor efficacy in epithelial ovarian cancer has been demonstrated in clinical trials, the significance of HRD status in MCT-SCC has not previously been described.

CASE PRESENTATION

A 73-year-old woman underwent emergency laparotomy due to ovarian tumor rupture. The ovarian tumor was strongly adherent to the surrounding pelvic organs and could not be completely resected. The postoperative diagnosis was stage IIIB MCT-SCC (pT3bNXM0) of the left ovary. After surgery, we conducted the myChoice CDx. The genomic instability (GI) score of 87 was remarkably high, and there was no BRCA1/2 pathogenic mutation. After six courses of combination therapy with paclitaxel and carboplatin, the residual tumors had shrunk by 73 %. We performed interval debulking surgery (IDS), and the residual tumors were completely resected. Subsequently, the patient underwent two courses of the combination of paclitaxel, carboplatin, and bevacizumab, followed by maintenance therapy with olaparib and bevacizumab. Twelve months after IDS, no recurrence has been observed.

CLINICAL DISCUSSION

The present case suggests that there are some HRD cases among MCT-SCC patients and that IDS and maintenance therapy with PARP inhibitors may be effective in such cases, as in epithelial ovarian cancer.

CONCLUSION

Although the frequency of HRD-positive status in MCT-SCC remains unknown, HRD testing may provide appropriate treatment options for advanced MCT-SCC.

Sebaceous Carcinoma Arising in Ovarian Teratoma: First Report Associated With Germline Mismatch Repair Gene Mutation

Sebaceous carcinoma is an uncommon primary cutaneous neoplasm which may be associated with mismatch repair (MMR) abnormalities and sometimes with Muir-Torré syndrome. These neoplasms rarely arise in the ovary within a teratoma/ dermoid cyst. We report a sebaceous carcinoma arising in an ovarian teratoma in a 49-yr old (the 14th case reported in the literature) which exhibited loss of expression of MMR proteins MSH2 and MSH6. A germline mutation c.1102C>T was present in exon 7 of the MSH2 gene, the first report of a germline mutation associated with this tumor type. In reporting this case, we review prior reports of primary ovarian sebaceous carcinoma. We recommend that all sebaceous carcinomas of the ovary undergo immunohistochemistry for MMR proteins for investigation of possible Lynch syndrome.

High homogeneity of MMR deficiency in ovarian cancer

OBJECTIVE

Mismatch repair (MMR) deficiency and Bethesda panel microsatellite instability (MSI) are increasingly analyzed to identify tumors that might benefit from immune checkpoint inhibitors, but tumor heterogeneity is a potential obstacle for such analyses. In ovarian cancer, data on intratumoral heterogeneity of MMR deficiency/MSI are lacking.

METHODS

N = 582 ovarian cancers were screened for MMR deficiency by immunohistochemistry (IHC) on a tissue microarray. 10 cases suspect for MMR deficiency were identified among 478 interpretable cancers and repeated IHC on large sections combined with polymerase chain reaction (PCR)-based MSI analysis validated MMR deficiency/MSI in 9 of these tumors.

RESULTS

MMR deficiency/MSI was predominantly seen in endmetrioid cancers (8 of 35, 23%) and also in 1 of 358 serous carcinomas (0.3%), but was absent in 34 mucinous carcinomas, 23 clear cell carcinomas, 17 malignant mixed Mullerian tumors (carcinosarcomas), and 11 mixed carcinomas. MMR deficiency involed protein loss of PMS2/MLH1 in 6 cases and of MSH2 and/or MSH6 in 3 cases. 7 MMR deficient cancers were MSI-high (all endometrioid), one was MSI-low (endometrioid) and one cancer with unequivocal MMR protein loss exhibited microsatellite stability (serous). MLH1 promotor methylation was observed in 4 of 5 endometrioid cancers with MLH1 protein loss. Immunostaining of all available cancer-containing tissue blocks (n = 114) of tumors with confirmed MMR deficiency/MSI revealed uniform MMR status throughout the entire tumor mass.

CONCLUSIONS

Our data show that MSI is present in a substantial proportion of endometrioid ovarian cancers but can also occur in other tumor subtypes. MMR deficiency/MSI typically involves the entire tumor mass, suggesting that MMR inactivation occurs early in tumorigenesis in a subset of ovarian cancers.