Disseminated struma ovarii containing focal anaplastic carcinoma in peritoneal implants: a case report

Malignant changes in struma ovarii have been defined using histopathologic criteria for carcinomas of the cervical thyroid gland. We report a case of struma ovarii with extensive extraovarian spread containing a small focus of anaplastic carcinoma (AC) in peritoneal implants. AC arising in benign-looking struma ovarii with peritoneal implants has not been reported. Multiple pelvic masses were identified on abdominopelvic computed tomography in a 38-yr-old woman. An exploratory laparotomy revealed multiple, variable-sized masses on the omentum, and colonic and uterine serosa. A microscopic but grossly unidentifiable lesion in the right ovary had a histologic appearance that mimicked hyperplastic follicular epithelium of nodular thyroid goiter. Multiple peritoneal implants showed histology similar to the ovarian lesions except a focal area of AC in the omental mass. Anaplastic cells demonstrated characteristic immunoreactivity for p53, cyclin D1, and a high Ki-67 index of about 30%, with loss of expression of thyroid transcription factor-1 and thyroglobulin, whereas the remaining goitrous background showed opposite expression patterns in all aspects. Furthermore, the areas of AC showed p53 mutation by molecular analysis. The AC harboring p53 mutation within extraovarian spread suggests that disseminated struma ovarii mimicking nodular goiter has potential for histologic progression through similar pathogenetic mechanism with cervical thyroid carcinoma despite the innocuous appearance.