Cytologic clues for distinguishing the tall cell variant of thyroid papillary carcinoma. A case report

In contrast to typical papillary carcinoma, the tall cell variant (TCV) of thyroid papillary carcinoma has more aggressive biologic behavior. Attempts to make a specific diagnosis of TCV of papillary carcinoma based on fine needle aspiration cytology (FNAC) have been unsatisfactory.

The cytologic and histologic study of one such case was made with an emphasis given to identifying the main histologic criteria for the specific diagnosis of TCV of papillary carcinoma in FNAC smears. "Tall cells" were defined as cells with abundant eosinophilic, elongated cytoplasm; the height of these cells was twice their width or more, and they have to constitute > 30% of the tumor cell population. Tall cells were not found in smears of 20 cases of nonaggressive papillary carcinomas investigated as control cases. Only one mitotic figure was found in one slide of one of the control cases (5%) in comparison to two and three mitotic figures found in the two slides of TCV of papillary carcinoma.

In addition to conventional cytologic features of typical papillary carcinoma, the identification of both tall cells and mitotic figures in the same smears is highly indicative of TCV of papillary carcinoma. More studies will be necessary to confirm the usefulness of this clue.