Columnar cell carcinoma of the thyroid. Fine needle aspiration findings in a case.

Columnar cell carcinoma is a recently described rare tumor of the thyroid. The fine needle aspiration cytologic findings of one example are reported. In the smears, the tumor fragments showed papillary and glandular patterns. The tumor cells were columnar and exhibited pseudostratification of the nuclei. The nuclei were oval to elongated and possessed stippled chromatin and inconspicuous nucleoli; occasional ones exhibited longitudinal grooving. It is important to distinguish this tumor from papillary carcinoma of thyroid because of its much more aggressive behavior, from metastatic adenocarcinoma for obvious treatment considerations, and from medullary carcinoma.