Gastrointestinal adenocarcinoma arising in a mature cystic teratoma of the ovary.

Background: Mature cystic teratoma of the ovary (MCTO) is the most common ovarian germ cell neoplasm and is usually diagnosed in early adulthood. Malignant transformation is rare, occurring in approximately 2% of all cases. Though malignant transformation can occur from any of the embryonic germ layers, the most common malignancy arising in these otherwise benign tumors is squamous cell carcinoma.

Case: We present a patient with a MCTO where malignant transformation of gastrointestinal epithelium resulted in moderately differentiated adenocarcinoma. After 3 years of follow-up, she remains free of disease.

Conclusion: Although gastrointestinal epithelium is often found in MCTOs, adenocarcinoma arising from this cell type is uncommon. This is the third reported case of adenocarcinoma arising in gastrointestinal epithelium of a MCTO.