Abstract
A 71-year-old man visited a local physician in July 2012 with pain and swelling in the coccyx. He was diagnosed with a coccygeal cyst, and incision resulted in discharge of a jelly-like fluid. An adenocarcinoma was diagnosed based on biopsy of the cyst wall, and the patient was referred to our hospital for surgery. A 4-cm tumor accompanied by hard nodules was seen in the hip between the coccyx and the anus from the skin to the subcutaneous layer. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a 4-cm tumor consisting of both solid and cystic parts in the subcutaneous layer of the tip of the coccyx and the postanal space. Transsacral surgery was performed under general anesthesia with the patient in the jackknife position, and the tumor was resected together with areas of skin infiltration. The pathological diagnosis of the cyst wall was a tailgut cyst, and adenosquamous carcinoma was seen in the thickened cyst wall. Local recurrence occurred in the hip in the fourth postoperative month, and multiple lung metastases were seen in the sixth postoperative month.
Malignant transformation of tailgut cyst is extremely rare, and only six cases have been reported to date in Japan. Our experience with a case of adenosquamous carcinoma that developed from a tailgut cyst is reported with reference to the literature.
