Peritoneal and mediastinal highly differentiated follicular carcinoma of ovarian origin.

A 70-year-old female patient presented to her primary care doctor with persistent elevated alkaline phosphatase of suspected metastatic etiology. Computed tomography demonstrated epicardial and peritoneal nodules. Biopsy of one of the peritoneal nodules revealed thyroid tissue and extraovarian struma ovarii was considered. The patient had a history of remote total abdominal hysterectomy and bilateral salpingo-oophorectomy 31 years prior for endometriosis with no available pathology from that surgery. The patient recalls being told that she had a left ovarian cyst. A thyroid ultrasound was performed that demonstrated multiple nodules without concerning features; however, due to high clinical suspicion, a total thyroidectomy was performed. Upon full histological evaluation a 0.5 cm papillary microcarcinoma was found. Given the rarity of metastatic papillary cancer to the peritoneum and the small size and grade of the tumor, a diagnosis of highly differentiated follicular carcinoma of ovarian origin was favored. The patient was subsequently treated with radioiodine therapy.