A 62-year-old postmenopausal woman has a 14 cm cystic ovarian mass present for many years, recently enlarging rapidly. Excision shows a mature cystic teratoma whose wall contains a firm white plaque. Histology of the plaque shows infiltrating keratinising nests of atypical squamous cells. What is the diagnosis, and what is the strongest predictor of outcome?

• A Squamous cell carcinoma arising in mature cystic teratoma, completeness of surgical resection predicts outcome ✓
• B Immature teratoma, grade of immature neuroepithelium predicts outcome
• C Metastatic cervical carcinoma, HPV status predicts outcome
• D Transitional cell carcinoma, stage at diagnosis predicts outcome

Explanation

Malignant transformation complicates roughly 1 to 2 percent of mature cystic teratomas, almost always in postmenopausal women with long-standing cysts, and squamous cell carcinoma is by far the most common transformed component. Prognosis depends chiefly on whether complete resection with intact capsule removal is achieved, since rupture or incomplete excision carries a poor outlook. Immature teratoma is defined by immature neuroectoderm, which is absent here.

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

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Written and medically reviewed by the StethoPrep medical team.