A 35-year-old woman presents with a pelvic mass, abdominal distension, and symptoms of hyperthyroidism (palpitations, weight loss, tremors). Serum free T4 is elevated and TSH is suppressed. Pelvic ultrasound reveals a 10 cm predominantly solid left ovarian mass. Which ovarian tumor is MOST likely responsible?

• A Struma ovarii ✓
• B Mature cystic teratoma (dermoid cyst) with squamous cell carcinoma transformation
• C Cystadenofibroma
• D Sertoli-Leydig cell tumor

Explanation

Struma oovi is a monodermal teratoma composed predominantly of mature thyroid tissue. It is the most common cause of ectopic thyroid tissue causing hyperthyroidism in the ovary. Grossly it appears as a solid, tan-brown, lobulated mass. Mature teratomas rarely cause hyperthyroidism. Sertoli-Leydig tumors produce androgens, not thyroid hormones.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.