MULTINUCLEATE GIANT-CELLS IN PAPILLARY THYROID-CARCINOMA - A MORPHOLOGIC AND IMMUNOHISTOCHEMICAL STUDY

Multinucleate giant cells (MGCs) occur in a variety of inflammatory, h yperplastic, and neoplastic thyroid disorders. They also have been rec ognized as a feature of papillary thyroid carcinoma (PTC), particularl y in fine-needle aspiration biopsies (FNAB). However, the origin of th e MGCs and their comparative frequencies in histologic and cytologic p reparations have not been established. Therefore, histologic sections from 76 cases of PTC were examined and immunohistochemical analyses fo r epithelial and histiocytic markers were performed. Giant cells were identified in histologic sections of 35 cases (46%) of PTC. In cytolog ic preparations, MGCs were identified in 12 of 22 cases (55%). MGCs we re present within follicles or adjacent to papillae, and were often as sociated with resorption of colloid. Immunohistochemical results indic ated that MGCs were of histiocytic rather than epithelial origin. Mult inucleate giant cells in PTC most likely represent a response to leaka ge of colloid into the interstitium. Although MGCs have been described most commonly in inflammatory conditions of the thyroid, the results of this study suggest that their presence should prompt a careful appr aisal of associated PTC.