Tailgut cyst associated with a carcinoid tumor: case report and review of the literature.

We report the case of a 49-year-old woman who presented a tailgut cyst lined by a variety of epithelium including squamous, columnar and transitional. Fortuitously a microscopic carcinoid tumor expressing immunohistochemically neuroendocrine markers was identified in the cystic wall. Tailgut cysts are congenital abnormalities located in the presacrococcygeal area occurring usually in adult patients. Clinical diagnosis is difficult because they are often asymptomatic. Patients may present symptoms resulting from local mass effects or complications. The differential diagnoses include rectal duplication cysts, cystic sacrococcygeal teratomas, epidermal cysts, epidermoid cysts, anal duct or gland cysts. Magnetic resonance imaging has recently become the modality of choice to image the cyst. Malignant transformation is rare; 23 cases including 10 carcinoid tumors have been reported in the literature. To our knowledge, this is the eleventh case of carcinoid tumor arising in a tailgut cyst.