Squamous cell carcinoma associated with tall cell variant of papillary carcinoma of the thyroid.

We report the simultaneous occurrence of the tall cell variant of papillary carcinoma and squamous cell carcinoma in the thyroid gland. Histology and immunohistochemical findings are discussed and it seems that the malignant squamous component was transformed from the tall cell variant of papillary carcinoma. Metastasis from the squamous cell carcinoma is diagnosed in the regional lymph node.