A rare case of collision tumor: Massive mucinous cystadenoma and benign mature cystic teratoma arising in the same ovary

Collision tumor means the coexistence of two adjacent, but histologically distinct tumors without histologic admixture in the same tissue and is rare incidence involving the ovary. There are instances of collision tumors consisting of teratoma with serous cystadenocarcinoma, mucinous cystadenocarcinoma, and/or granulosa cell tumor. The possible existence of an ovarian collision tumor should carefully be examined pre- and post-operatively and histologically, so as to avoid misdiagnosis of a possible malignancy. We describe the findings in a histopathologically proven case of a massive mucinous cystadenoma and benign mature cystic teratoma arising in the same ovary.