Follicular variant of papillary carcinoma of the thyroid: fine-needle aspirates with histologic correlation.

Crile and Hazard reported in 1953 a follicular pattern of papillary thyroid carcinoma. Little has been said about this pattern in the cytologic literature. From more than 8,000 thyroid aspirates in our files, we reviewed all those diagnosed as "follicular variant of papillary carcinoma," "suspect follicular variant of papillary carcinoma," and "follicular neoplasm vs. follicular variant of papillary carcinoma." Also, we reviewed all aspirates in which a diagnosis of follicular variant of papillary carcinoma had been made on surgically excised glands, regardless of the cytologic diagnosis; 63 aspirates from 45 patients were collected. All smears were air-dried and stained with Diff-Quik. Most smears were very cellular ("tumor cellularity"), and the neoplastic follicular cells formed empty follicles, rosettes, tubules, and papillary structures. Nuclei were twice the size of red blood cells, had smooth contours, were hyperchromatic, and varied in shape but not much in size. Nuclear overlapping was common. Some nuclei had one small and almost pointed end, thereby resembling arrowheads. Intranuclear inclusions, multinucleated histiocytes, and psammoma bodies were uncommon. Pink-stained colloid was frequent.