A 30-year-old woman presents with a 7 cm unilateral ovarian mass on ultrasound. Histopathology reveals mature thyroid tissue comprising more than 50% of the tumor, with no other germ cell elements. Which is the most likely diagnosis?
- A Mature cystic teratoma (dermoid cyst)
- B Monodermal teratoma with carcinoid
- C Struma ovarii ✓
- D Immature teratoma
Correct answer: C. Struma ovarii
Explanation
Struma ovarii is a monodermal teratoma composed predominantly of mature thyroid tissue. When thyroid tissue constitutes over 50% of a dermoid, it is classified as struma ovarii. Though dermoid cysts contain ectodermal elements, a dominant thyroid component makes struma ovarii the specific diagnosis. Carcinoid is another monodermal variant but contains neuroendocrine tissue.
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.