RESUMEN
The most common form of malignant transformation developing from a mature cystic teratoma is squamous cell carcinoma, representing 80% of malignant transformations, while adenocarcinoma accounts for approximately 5%. Because of this rarity, few reports exist of preoperative diagnosis of this tumor by magnetic resonance imaging, in particular with fat suppression techniques. Here, we report magnetic resonance imaging findings and clinical features of a 79-year-old woman with mucinous adenocarcinoma arising from a mature cystic teratoma (measuring 5x6 cm), classified as surgical stage IA. Because of the poor prognosis of malignant transformation, when mature cystic teratomas are detected (even smaller than 5 cm tumor size) in postmenopausal women, serum tumor marker carcinoembryonic antigen levels and fat-suppressed magnetic resonance imaging may be potential indicators of malignant transformation.