Ovarian sex cord tumors with annular tubules: an ultrastructural study.

The ultrastructural features of two "sex cord tumors with annular tubules" are presented. The findings are compared with the reported fine structure of ovarian and testicular stromal cells and the cells of gonadal stromal neoplasms. The predominant cell in the "sex cord tumor with annular tubules" has some of the ultrastructural features found in gonadal stromal cells of either ovarian or testicular type; however, no Charcot-Bottcher crystals, lamellar bodies, crystalloids of Reinke, abundant smooth endoplasmic reticulum or complex plasma membrane interdigitations are observed in the tumor cells to suggest wither Sertoli or Leydig cell origin. The striking similarity between the predominant cell type and granulosa cells, as well as the presence of fibrillary material of the type seen in Call-Exner bodies, suggests a granulosa cell origin for these neoplasms. However, the presence of a sparsely distributed second cell type which closely resembles the dark cells in normal nonluteinized ovarian stroma indicates these tumors may arise from the nonspecialized ovarian stroma.