Ovarian small cell carcinoma. Histogenetic considerations based on immunohistochemical and other findings.

Small cell carcinoma of the ovary is a rare, poorly understood aggressive tumor of young women, associated with paraendocrine hypercalcemia in two-thirds of the cases. Immunohistochemical staining of 15 small cell carcinomas, one-third of which were associated with hypercalcemia, 15 adult granulosa cell tumors, 15 juvenile granulosa cell tumors, and 5 Sertoli cell tumors, was performed with the use of antibodies against cytokeratins (AE-1/AE-3, CAM 5.2, 902), epithelial tumor-associated antigens (B72.3, epithelial membrane antigen [EMA]), vimentin, S-100, neuron-specific enolase (NSE), lysozyme, parathyroid hormone, and chromogranin-A in an attempt to define histogenetically this tumor type. One-third of the small cell carcinomas were positive for EMA, whereas all of them were negative for B72.3 and S-100. In contrast, one-third of the granulosa cell tumors were positive for S-100 and all of them were negative for EMA and B72.3. One of five Sertoli cell tumors were positive for EMA and two were positive for B72.3, but all were negative for S-100. Differences existed in the frequency, intensity, and/or pattern of staining for cytokeratin, vimentin, lysozyme, and NSE among the various tumor types. A single small cell carcinoma from a patient with hypercalcemia stained focally for parathyroid hormone, whereas all 30 granulosa cell tumors and 4 of 5 Sertoli cell tumors were nonreactive. Chromogranin-A staining was noted in four of five small cell carcinomas, none of ten granulosa cell tumors, and two of five Sertoli cell tumors. These immunohistochemical findings, as well as previous light and electron microscopic data, do not clearly indicate any specific cell as the cell of origin of the ovarian small cell carcinoma.