Squamous cell carcinoma arising from thyroglossal duct remnants: report of a case and results of immunohistochemical studies.

We report on the case of a 57-year-old male found to have squamous cell carcinoma (SCC) arising from thyroglossal duct remnants. The patient presented with an asymptomatic tumor in his anterior neck which was immovable on palpation. Aspiration biopsy cytology revealed class V malignancy with many atypical clusters and marked keratinization. After preoperative radiation, a radical operation employing Sistrunk's procedure with bilateral neck dissection was performed. Histopathological examination confirmed a diagnosis of moderately differentiated SCC, but revealed ciliated columnar epithelium in the walls of the cyst without a normal layer of squamous cells. Furthermore, immunohistochemical studies demonstrated the tumor to be negative for thyroglobulin staining, but positive for cytokeratin and carcinoembryonic antigen. These histopathological findings proved attributable to squamous metaplasia occurring in the ciliated columnar epithelium of the thyroglossal duct. Thus, SCC might originate in the metaplastic portion of the thyroglossal duct remnants. Although the prognosis associated with SCC in the thyroglossal duct is not as optimistic as that associated with papillary carcinoma, no evidence of recurrence has been observed in this patient in the 7 years since his operation. This suggests the effectiveness of our therapeutic approach for this unusual disease.