Can the Tall Cell Variant of Papillary Thyroid Carcinoma Be Distinguished from the Conventional Type in Fine Needle Aspirates? A Cytomorphologic Study with Assessment of Diagnostic Accuracy

OBJECTIVES: The tall cell variant of papillary thyroid carcinoma (TCV-PTC) is an aggressive variant of PTC requiring accurate cytopathologic diagnosis for early aggressive management. STUDY DESIGN: Twenty-five cases of TCV-PTC in which the tall cells comprised at least 30% of surgically resected tumor were included in the study. The direct smears from a preoperative fine needle aspiration (FNA) and available hematoxylin and eosin cell block sections were reviewed. Ten cases of TCV-PTC were randomly selected and blinded with an equal number of conventional PTC cases. Representative slides were independently reviewed by 7 cytologists. RESULTS: In a majority of the cases, the FNA direct smears were hypercellular and displayed flat monolayer sheets of cells. Tall columnar cells with cytoplasmic tails were seen in 56% of cases. The presence of large polygonal follicular cells with abundant granular oncocytic cytoplasm and distinct cell borders was the most common feature seen in all cases. Seventeen (68%) cases displayed intranuclear pseudoinclusions in cells with abundant granular cytoplasm. A correct diagnosis of TCV-PTC was made in 30-40% of cases by 7 study participants. CONCLUSIONS: The correct recognition of TCV-PTC features in preoperative FNA is important for clinical management, and reporting these features in a cytopathology report is suggested.