Correlation of cytologic and histologic features in variants of papillary carcinoma of the thyroid

Different morphologic variants have been described for papillary carcinoma of the thyroid, but little emphasis has been placed on their cytologic patterns. We studied fine needle aspiration (FNA) smears and histologic sections from 48 cases of papillary carcinoma, including 24 of the usual type, 13 of the follicular variant, 7 of the encapsulated variant and 4 of the tall cell variant, in an attempt to correlate the cytologic features and the different histologic variants. Single cells, monolayers and papillary fragments were present in all the variants. The presence of follicles was not restricted to the follicular variant. Nuclear grooves and cytoplasmic pseudoinclusions were present in most of the cases, with nuclear grooves the most common finding in all the variants (92.3-100%). Psammoma bodies were an infrequent finding (0-25%) and were absent from the follicular variant. Colloid was present in all the variants and was a frequent finding in the follicular variant (84.6%). The findings suggest that the exact histologic variant of papillary carcinoma cannot be predicted from the appearance of the fine needle aspirate.