Malignant Struma Ovarii With Papillary Thyroid-Type Cancer

What happened, in summary

A 46-year-old woman had persistent dull pelvic pain and underwent removal of her left ovary and fallopian tube for an adnexal mass. Pathology established malignant struma ovarii, a rare ovarian tumor made up of thyroid-type tissue. Two months later, she underwent more extensive surgery, including hysterectomy, removal of the right ovary and tube, omentectomy, pelvic lymph node surgery, and treatment of other involved abdominal and pelvic tissues.

Pathology showed papillary thyroid-type cancer involving multiple pelvic and abdominal sites. Testing of the tumor found a KRAS mutation. Because a small thyroid nodule was also seen, she later underwent total thyroidectomy to determine whether the thyroid itself was the primary source. The thyroid showed nodular goiter rather than thyroid cancer, supporting an ovarian origin.

She then received radioactive iodine treatment and continued TSH-suppressive therapy with ongoing monitoring. Whole-body radioactive iodine scans showed no evidence of remaining local or distant disease. At 12 months from the initial diagnosis, she was well and symptom-free. Her course involved extensive pelvic and abdominal spread followed by treatment and disease-free follow-up imaging.