Immunocytochemical evaluation of thyroid neoplasms on thin-layer smears from fine-needle aspiration biopsies.

BACKGROUND: Fine-needle aspiration biopsy (FNAB) is the most reliable diagnostic tool for thyroid nodules. A difficult cytologic diagnosis may be supported by an immunocytochemical study. The efficacy of a panel made up of RET, HBME-1, and Galectin-3 antibodies was evaluated in smears processed by thin-layer cytology (TLC). DESIGN: Thyroid FNABs (n = 99) with both conventional (CS) and thin-layer cytology (TLC) smears were studied. The cases were diagnosed as follows: 5 benign lesions (BL), 13 papillary carcinomas (PC), and 81 follicular proliferations (FP). The category of FP was divided into three subgroups according to nuclear features of follicular cells: Follicular neoplasm (FN NOS), oxyphilic follicular neoplasm (OFN), and follicular lesion with nuclear pleomorphism (FLWNP). Immunostains for HBME-1, Galectin-3, and RET were carried out on TLC slides. RESULTS: Among 49 cases undergoing surgery, all 10 PC and 2 BL were histologically confirmed, whereas 15 out of 37 FP (40.5%) were malignant. The complete immunocytochemical panel (ICCP) was positive in 9 of 10 malignancies (90%) and negative in both BLs. Out of 37 FP, the ICCP yielded positive in 15 cases (4 benign, 11 malignant) and negative in 11 (all benign). In the FLWNP subgroup, the ICCP was positive in 11 (84.6%) and negative in 2 histologically benign cases. CONCLUSION: The combined panel of antibodies and the nuclear pleomorphism of follicular cells were effective in distinguishing between thyroid nodules requiring surgery from thyroid nodules requiring just follow-up. 2005 American Cancer Society.