Cytopathology of papillary carcinoma of the thyroid with anaplastic transformation. A case report.

A case of papillary carcinoma of the thyroid with anaplastic transformation was diagnosed by fine needle aspiration. The atypical history and presentation of this case, the initially problematic cytologic and immunohistochemical findings, and the definitive cytologic and histologic features are described. The diagnostic problems posed by papillary carcinoma of the thyroid with anaplastic transformation are discussed. This diagnosis must be included in the differential diagnosis of poorly differentiated tumors of the neck.