Struma ovarii, as a monodermal variant of ovarian teratoma, constitutes about less than 3% of ovarian teratomas. It is difficult to be macroscopically recognized. Multiple appearances under microscope serve as another reason to mislead the accurate pathologic evaluation. Here, we report an unusual case of struma ovarii occurred in a 77 years old woman, which is currently known as the oldest age for this disease. The frozen section morphologically showed sex cord like elements and was suspicious for a sex-cord stromal tumor, probably a Sertoli cell tumor. Final pathological diagnosis was confirmed as struma ovarii based on the typical morphologic thyroid follicles and immunohistochemical staining results.
Keywords: Struma ovarii; ovary; sertoli cell tumor.