Small Cell Carcinoma of the Ovary: Clinicopathologic and Immunohistochemical Analysis of 7 New Cases of a Rare Malignancy

Background Small cell carcinoma of ovary (SCCO) is extremely rare. Two types of SCCO are recognized, the pulmonary type (SCCOPT) and the hypercalcemic type (SCCOHT). Establishing an accurate diagnosis is challenging, owing to its rarity and paucity of data describing the distinctive histopathologic and immunohistochemical (IHC) features. Methods This was a retrospective study conducted over a period of 4 years. All cases reported as SCCO on histopathology were retrieved. All the available clinical, histopathological, and IHC features were studied in detail. Results A total of 7 cases of SCCO were diagnosed during the study period. There were 4 cases of SCCOPT and 3 cases of SCCOHT and with mean age of 57.25 and 22 years, respectively. All the cases presented as stage IV disease. Among the SCCOPT cases, 3 showed bilateral involvement with 1 showing concurrent uterine endometrioid adenocarcinoma. Microscopy revealed small hyperchromatic cells with brisk mitosis and multifocal necrosis. On IHC, these were consistently positive for chromogranin, CD56, and synaptophysin. All the SCCOHT cases showed unilateral involvement. Microscopically, in addition to small hyperchromatic cells, larger “rhabdoid” tumor cells were also seen. On IHC, chromogranin was negative, with positivity for vimentin and epithelial membrane antigen. The expression of SMARCA4/BRG1 was lost while SMARCB1/INI1 was retained in all cases. All of these patients developed recurrence and died due to disease progression despite treatment. Conclusions SCCO is an extremely infrequent ovarian malignancy with poor prognosis. Knowledge about its characteristic features is important for accurate tissue diagnosis and appropriate management.