Adenosquamous carcinoma arising in a thyroglossal duct cyst: report of a case.

A 61-year-old Japanese woman had an 11-year history of an enlarging anterior neck mass that was diagnosed otolaryngologically as a thyroglossal duct cyst. Preoperatively, fine-needle aspiration cytology suggested a neoplastic lesion, but no obvious malignancy was clinically evident. Sistrunk's operation was performed. An adenosquamous carcinoma arising in a thyroglossal duct cyst was found on pathological examination. Carcinoma arising in a thyroglossal duct cyst is rare, and only approximately 200 cases have been reported, most of which were papillary carcinoma. Only 21 cases of squamous cell carcinoma arising in a thyroglossal duct cyst have been reported. The present case is the first report of adenosquamous carcinoma arising in a thyroglossal duct cyst.