RESUMEN
A collision tumor is the coexistence of two adjacent, but histologically distinct tumors without histological admixture in the same tissue or organ. Such tumors have often been reported in various organs, but location in the ovary is rare. The juxtaposition with dermoid cysts has been reported as comprising approximately 5% of benign mucinous ovarian tumors and rare examples of proliferating mucinous tumors. Authors are reporting a case of collision tumor which included benign mucinous cystadenoma and benign cystic teratoma. The gynecologists and pathologists should be aware of such combination of tumors. The case was diagnosed post-operatively. It is important to correctly diagnose the component of tumor for further management and favourable prognosis. Frozen section intra-operatively plays an important role in diagnosing such tumors.