Well-Differentiated Papillary Mesothelioma With Two Synchronous Serous Gynaecologic Carcinomas in a 62-Year-Old Woman: Lessons Learned for the Gynaecologic Surgeon.

BACKGROUND: Well-differentiated papillary mesothelioma (WDPM) is a rare tumor of unknown malignant potential. It is typically diagnosed incidentally during benign gynaecologic surgery. We report the first published case of WDPM in a woman with synchronous serous carcinomas of the gynaecologic tract and highlight lessons learned for general gynaecologists and gynaecologic oncologists alike. CASE: A 62-year-old woman was referred for assessment and management of a pelvic mass. Intraoperatively, metastatic high-grade carcinoma was identified and the patient underwent a successful debulking procedure that identified 3 synchronous tumors: ovarian high-grade serous carcinoma, endometrial serous carcinoma, and 2 foci of pelvic WDPM. CONCLUSION: This case of WDPM with 2 synchronous serous gynaecologic tumors is a novel addition to the reported literature and offers many learning points about the disease. Gynaecologic surgeons should be familiar with WDPM, as it is predominantly found in reproductive-aged women undergoing benign gynaecologic surgery, may be linked with endometriosis, and has an unclear malignant potential. Multidisciplinary care is essential for accurate diagnosis. Further research is needed to clarify the optimal management and surveillance of WDPM.

Interobserver Agreement for Mismatch Repair Protein Immunohistochemistry in Endometrial and Nonserous, Nonmucinous Ovarian Carcinomas.

Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is an established test to identify Lynch syndrome (LS) in patients with colorectal cancer and is being increasingly used to identify LS in women with endometrial and/or nonserous ovarian cancer (OC). We assessed interobserver agreement in the interpretation of MMR-IHC on endometrial and ovarian carcinomas. The study consisted of 73 consecutive endometrial cancers (n=48) and nonserous, nonmucinous epithelial OCs (n=25). Six pathologists from 2 cancer centers, one with and the other without, previous experience in interpreting MMR-IHC, evaluated MLH1, MSH2, MSH6, and PMS2 stains. Before the study, an experienced pathologist led a review of 9 teaching cases. A decision tool was developed as a guide in MMR-IHC interpretation. Staining was interpreted as intact, deficient, or equivocal for each protein. Interobserver agreement for the patient MMR status was categorized as "almost perfect" with κ=0.919 (95% CI, 0.863-0.976). All observers were in agreement in 66 (92%) tumors. Four of the less experienced pathologists had at least 1 discrepant interpretation. There were 6 discordant cases: 3 MMR-deficient cases and 2 MMR-intact cases by majority opinion were called equivocal by at least 1 observer, and 1 MMR-deficient case by majority opinion was interpreted as MMR intact by 1 pathologist. Only the latter case (1/73 patients, 1.4%) had an unequivocal disagreement that could affect patient management. Issues associated with discordant interpretation included heterogeneous staining, intratumoral lymphocytes, regional reduced internal control tissue staining, and scattered absent/weak staining adjacent to tumor cells with strong nuclear staining.