Multinucleated giant cells in fine-needle aspiration of thyroid nodules: Their diagnostic significance

Multinucleated giant cells (MNGCs) are reported in many thyroid lesions. Th is study examines whether their quantity and quality can help in the differ ential diagnosis. All fine-needle aspirations (FNAs) of the the thyroid wit h a "significant" number of MNGCs were reviewed from 1995 -1998. There were 23 cases (<1% of thyroid FNAs): 8 papillary carcinomas (PC), 4 subacute th yroiditis (ST), 3 granulomas, 7 adenomatous goiters (AG), and one Hurthle-c ell adenoma (HA). MNGCs with dense cytoplasm were seen exclu sively in PC, ST, and granulomas. They had angulated shapes. They were most numerous, lar gest, and with the highest number of nuclei in ST and granulomas. MNGCs wit h foamy cytoplasm were seen in AG and HA and 80% of the other cases (PC, ST , and granulomas). In PC, rare MNGCs had intranuclear inclusions and groove s. The accompanying cell population was characteristic of each disease. The quantity and quality of MNGCs in thyroid FNA may be helpful in nan owing t he differential diagnosis. Diagn. Cytopathol. 1999;21:307-312. (C) 1999 Wil ey-Liss, Inc.