Fine needle aspiration cytology of follicular variant of papillary carcinoma of the thyroid: Morphologic pointers to its diagnosis

OBJECTIVE: To study the cytomorphologic features of 59 cases of histologically proven follicular variant of papillary carcinoma (FVPC), compare them to those described in the literature and highlight cytologic features that may aid in the preoperative diagnosis. STUDY DESIGN: Aspiration smears from 59 histologically proven cases of FVPC were examined independently by 2 observers, and a detailed cytologic evaluation was done for architectural, cytologic and nuclear features. surgical RESULTS: On initial cytology of the 59 cases, 36 (61%) were diagnosed aspapillary carcinoma, and 17 of these were subtyped as FVPC. On reviewing the smears, 50 cases were diagnosed as papillary carcinoma, and 33 of them were typed as FVPC; however, 4 cases were diagnosed as benign lesions. Most smears showed moderate to high cellularity, with 55 cases (93%) showing syncytial clusters and 48 (81%) showing microfollicular architecture. Chromatin clearing and nuclear grooves were seen in 55 (93.2%) and 54 (91.52%) cases but were easily detected in only 36 (61%) and 44 (74%) cases, respectively. Thick colloid was identified in 28 cases, and 3 of these cases also showed thin colloid in the background. CONCLUSION: Our findings suggest that syncytial clusters, microfollicular architecture, chromatin clearing and nuclear grooves are strong morphologic pointers to the diagnosis of FVPC.