A tailgut cyst found accompanying rectal cancer: report of a case.

Tailgut cysts are rare congenital lesions. To date, only four cases have been reported in Japan, and the occurrence of a tailgut cyst with rectal cancer has never been documented. We describe here the case of a patient in whom a tailgut cyst in the retrorectal space was associated with rectal cancer. Preoperative computed tomography scans and endorectal ultrasonography failed to identify the lesion as cystic, instead suggesting an involved lymph node. This case emphasizes the necessity for careful diagnosis of masses in the retrorectal space in patients with rectal cancer.