Torsion of Collision Tumor: Dermoid Cyst and Fibrothecoma with Postmenopausal Bleeding.

The term collision tumor refers to the coexistence of two adjacent but histological distinct tumors with no histological admixture at the interface. Collision tumors involving ovaries are extremely rare. A collision tumor composed of a dermoid cyst and fibrothecoma is extremely rare in menopausal women. The mechanism of the development of collision tumor is uncertain. During clinical evaluation, differentiation of characters of these ovarian tumors is important to decide appropriate treatment strategies and for good prognosis. We report an unusual clinical manifestation of the torsion of a dermoid cyst and fibrothecoma in the right ovary with postmenopausal bleeding.