Mature Cystic Teratoma with Co-existent Mucinous Cystadenocarcinoma in the same Ovary-A Diagnostic Dilemma

Mature cystic teratoma co-existing with a mucinous cystadenocarcinoma is an infrequently encountered entity with only a handful of cases reported till date. The possibilities in such a case are either a malignant transformation of a benign teratoma into adenocarcinoma or a collision tumor between a mature cystic teratoma and a mucinous tumour of either a primary ovarian surface epithelial-stromal origin or a secondary from a primary gastrointestinal tract tumour. The importance of distinguishing between the two entities has significant bearing on subsequent therapeutic management. We report a rare case of a mature cystic teratoma co-existing with a mucinous cystadenocarcinoma in the same ovary in a 44-year-old lady. Contrast Enhanced Computed Tomography (CECT) imaging of the left ovarian mass was suggestive of a teratoma but an intra-operative frozen section examination was reported as an adenocarcinoma with a cystic teratoma. Gross examination of the surgical specimen revealed a dermoid cyst with another multi-septated cystic lesion containing mucoid material. Histopathological examination showed a mature cystic teratoma and an associated well differentiated mucinous cystadenocarcinoma. The latter displayed a CK7-ve/CK20+ve immunoprofile. In absence of clinical, biochemical or radiological findings of a primary lower gastrointestinal tract tumour, the immunoprofile suggested the possibility of adenocarcinomatous transformation in a benign teratoma.