Hürthle Cell Neoplasms in Hematoxylin-Eosin-Stained Samples

Abstract

Hürthle cell neoplasms have been cytologically placed in a category distinct from follicular neoplasms in our past experience. Cytological features of hematoxylin-eosin-stained specimens diagnosed as “suspected Hürthle cell neoplasms” include that the aspirate is generally high cellular, is comprised exclusively of Hürthle cells, has well-defined cell borders with enlarged nuclei, has abundant granular cytoplasm, and has round, oval to polygonal nuclei sometimes with prominent macronucleoli. The background is usually clean or bloody with or without histiocytes. Hürthle cell metaplasia of follicular cells is seen in several conditions affecting the thyroid, displaying a range of cytological features that mimic those encountered in Hürthle cell neoplasms, constituting important diagnostic pitfalls. An admixture of regular follicular cells, oncocytes with highly pleomorphic in size, transition forms, degenerative changes with histiocytes, lymphocytes or colloid in the background, absent macronucleus could serve as the clues to the diagnosis of nonneoplastic Hürthle cell nodules.