Submucosal dermoid cyst of the rectum: report of a case.

Despite the relatively common incidence of sacrococcygeal dermoids, rectal cysts are uncommon. We report the case of a submucosal dermoid cyst occurring in the rectum. A 30-year-old woman visited the Gynecology Department because of pregnancy. A pelvic tumor was accidentally found during the checkup after miscarriage. A barium enema showed an anterior shift of the rectum by the presence of the tumor. Computed tomography and magnetic resonance imaging revealed a tumor located posterior to the rectum occupying almost the entire pelvic cavity, and the tumor was resected. The tumor was located in the submucosal layer of the posterior rectal wall and was well circumscribed. The resected tumor was a cyst entirely covered with a fibrous and firm capsule, which was filled with an amorphous white creamy substance. The histological findings showed the cyst consisting of a keratinizing stratified squamous epithelium with sebaceous gland and hair follicles, which was compatible with benign cystic teratoma. Primary rectal teratoma is very rare and only 36 cases have been reported in the literature worldwide. Furthermore, while the majority of cases were polypoid-shaped dermoid cysts protruding into the rectal lumen, only 3 cases were submucosal dermoid cysts. Therefore, such cases are considered to be extremely rare.