Concomitant benign serous cystadenoma with struma ovarii - An unusual combination of tumours from different origin, a case report and review of literature

Struma ovarii is a rare ovarian tumour of germ cell origin which accounts for less than 5% of all ovarian neoplasms. It can occur alone or in association with other non-germ cell epithelial ovarian neoplasms. The coexistence of struma ovarii with serous cystadenoma is extremely uncommon with only 6 cases reported so far until 2017. Herein, we report an extremely rare case of a 39-year-old woman who presented with an ovarian mass. Clinicoradiologically possibility of a right ovarian cyst with torsion was made. Histopathological examination revealed an unusual dual pathology – benign serous cystadenoma and struma ovarii. This case is reported to highlight the importance of extensive sampling and careful histopathological examination even in a grossly benign looking cystic lesion of the ovary. This case is presented due to its extreme rarity which can cause diagnostic dilemmas and to provide insight into rare entities and its prognostic significance.