Squamous Cell Carcinoma Arising in Thyroglossal Duct Remnant Cyst Epithelium

The extremely rare occurrence of invasive squamous cell carcinoma arising from normal epithelial lining of a thyroglossal duct remnant cyst is documented by demonstrating the histopathologic transition from normal squamous epithelium to squamous cell carcinoma. The requirements that must be fulfilled to accept a lesion as arising de novo from the epithelial lining are outlined, and all requirements are achieved. The lesion is differentiated from the less rare papillary or papillary-follicular adenocarcinoma of residual thyroid tissue of the thyroglossal duct tract remnants.