Carcinoid Tumor Arising within a Tailgut Cyst: A Case Report

ABSTRACT

Tailgut cysts are rare congenital lesions. They are believed to develop from remnants of the embryonic hindgut. Malignancy in tailgut cyst is extremely unusual. We experienced a case of a carcinoid tumor arising within a tailgut cyst at the presacral space. A 40-year-old woman was admitted for acute anal pain. Digital rectal examination revealed a 2-cm-sized submucosal tumor in the posterior midline rectum 4 cm above the anal verge. On sigmoidoscopic examination, the overlying rectal mucosa seemed to be intact. We performed a transanal incisional biopsy. The pathological diagnosis of the tumor biopsy revealed a malignant neuroendocrine tumor. The patient underwent an abdominoperineal resection. The tumor proved to be mutilocular cysts with a solid component. The cysts were diagnosed as tailgut cysts that were lined by a variety of epithelial types, including inner columnar cells, outer cuboidal cells, and transitional cells. The solid component in the cysts was confirmed as a carcinoid tumor on microscopic examination. Six months after the operation, she was found to have liver and brain metastases.