Cytology of columnar-cell variant of papillary thyroid carcinoma.

Columnar cell variant of papillary carcinoma (CCV-PC) thyroid is a rare and aggressive tumor composed of tall columnar cells that form papillae, glands and solid structures. This paper describes fine needle aspiration (FNA) cytologic features in a case of CCV-PC occurring in the right thyroid lobe of a 27-year-old female. Smears showed tall columnar cells in monolayered, three-dimensional, acinar and occasional papillary clusters. Nuclei were oval or elongated and monomorphic. Nuclear pseudostratification, resembling that seen in respiratory epithelial cells, was present in some of the cell clusters. Occasional cells showed squamous or Hurthle cell metaplasia. Nuclear grooves and intranuclear cytoplasmic inclusions were not seen. Sections of the right lobectomy specimen showed an well-encapsulated CCV-PC with capsular and vascular permeation. Tall cell variant of papillary carcinoma (TCV-PC) can be distinguished from CCV-PC by the oxyphilia of the tumor cells and the absence of nuclear pseudostratification. Colorectal and endometrial adenocarcinomas metastatic to the thyroid may be difficult to distinguish from CCV-PC.