Malignant struma ovarii.

BACKGROUND: A 25-year-old woman presented to her gynecologist with pelvic pain. Pelvic ultrasonography showed a 9 cm left ovarian mass. The patient underwent left oophorectomy, omental biopsy, and lymph node sampling. The ovarian mass proved to be a struma ovarii with numerous microscopic foci of papillary thyroid carcinoma. The patient had no symptoms of hyperthyroidism, and her thyroid function and serum thyroglobulin levels were normal. INVESTIGATIONS: Investigations included a pelvic ultrasound scan, histological examination of the ovarian mass and omental nodules, and lymph node sampling. DIAGNOSIS: Malignant struma ovarii. MANAGEMENT: The patient was referred to an endocrinology clinic for further investigations. Serum levels of TSH, thyroglobulin and thyroglobulin antibodies were measured. In addition, the patient underwent thyroid ultrasonography, which showed a 1 cm nodule that proved benign on biopsy. She was treated with thyroxine to reduce TSH secretion. Follow-up pelvic ultrasonography 1 year later showed no evidence of recurrent disease, and her serum thyroglobulin levels remained normal.