[Small cell carcinoma of the ovary of hypercalcaemic type: a clinicopathological analysis of sixteen cases].

Objective: To investigate the clinicopathological, molecular pathological features, and family genetic pedigree of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT). Methods: A total of 16 cases of SCCOHT diagnosed in Obstetrics and Gynecology Hospital of Fudan University from January 2013 to January 2023 were collected. The clinicopathologic features, SMARCA4/2/B1 protein expression, outcomes and SMARCA4 gene detection were reported. A follow-up study was also carried out. Results: The average age at diagnosis was 28.7 years (range 17-38 years). The preoperative calcium level was evaluated in 3 of 6 patients. The tumor was unilateral in all 16 cases, ranged from 8 to 26 cm (average 15.8 cm) in the greatest dimension. Extraovarian spread was present in 7 cases. In 10 cases, the tumors were initially misinterpreted as other ovarian neoplasms. BRG1 and BRM expression by immunohistochemistry were all lost in detected cases, while INI1 exhibited retained nuclear expression. All BRM-negative SCCOHTs also lacked BRG1 protein,but retained INI1 expression. SCCOHTs were only focally positive for EMA, CKpan, Calretinin, SALL4, and diffusely positive for WT1. Two of nine cases exhibited mutation-type p53 immunoreactivity. Ki-67 index was 58% on an average. ER, PR, FOXL2, α-inhibin, chromogranin A and LCA were negative in all the cases. SMARCA4 sequencing was available in 8 cases of SCCOHT, which revealed a germline SMARCA4 mutation in one patient, and others carried somatic mutation. Furthermore, two daughters, mother and an aunt of a patient with germline mutation were reported to be SMARCA4 mutation carriers. Follow-up was available for 15 patients, and the 6-month, 1-year and 2-year survival rate was 65.8%, 45.1%, and 22.6%, respectively. For patients in FIGO stages Ⅱ+Ⅲ, 6-month, 1-year survival rate was 53.6% and 35.7% respectively, compared to 80% (6-month) and 60% (1-year) in patients of staged I (P=0.358). Conclusions: With dismal prognosis of SCCOHT, accurate diagnosis is necessary. The typical age distribution, a panel of various staining results, especially concomitant loss of BRG1 and BRM may be of diagnostic aid and can be used to distinguish SCCOHT from its histological mimics. After the diagnosis of SCCOHT, genetic testing and genetic counseling are recommended.