A 58-year-old postmenopausal woman with a long-standing ovarian cyst presents with rapid abdominal enlargement and ascites. The cyst is excised and shows a mature cystic teratoma with a firm white nodule projecting into the lumen. Microscopy of the nodule shows islands of atypical squamous cells invading the wall. What is the most common malignant transformation in this setting?

• A Papillary thyroid carcinoma arising from strumal components
• B Adenocarcinoma arising from intestinal-type epithelium
• C Squamous cell carcinoma arising from the ectodermal (epidermal) component ✓
• D Malignant lymphoma arising from the lymphoid stroma

Explanation

Malignant transformation complicates roughly 1% to 2% of mature cystic teratomas, almost always occurring in postmenopausal women with long-standing cysts. The overwhelmingly commonest transformed element is squamous cell carcinoma arising from mature squamous epithelium of the ectodermal component, presenting as a mural nodule within the dermoid. Thyroid malignancies within struma ovarii, intestinal-type carcinoids, and other transformations occur far less frequently. Rapid growth of a previously stable dermoid in an older woman should raise this concern.

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.