Hürthle Cell Neoplasms in Papanicolaou- and Romanowsky-Stained Specimens

Abstract

Hürthle cell neoplasms are a distinct category of thyroid neoplasms that originate from metaplastic thyroid follicular epithelial cells. Hürthle cells are identified by the presence of abundant, granular cytoplasm that is brightly eosinophilic on hematoxylin and eosin staining and contain numerous mitochondria ultrastructurally. On alcohol-fixed Papanicolaou-stained slides, the cells have abundant green, blue, or orange cytoplasm, while on air-dried Romanowsky-stained slides, the cells have abundant blue or gray-pink cytoplasm. Both of these slide preparations are routinely examined in our practice on the vast majority of our thyroid specimens. A number of controversies have surrounded Hürthle cell neoplasms since their original description, including whether it is possible to separate benign from malignant Hürthle cell lesions cytologically, or even histologically. A number of entities, both neoplastic and nonneoplastic, that are in the differential diagnosis of Hürthle cell neoplasms are discussed. As do most laboratories in the United States, we categorize our thyroid aspirates according to the Bethesda System for Reporting Thyroid Cytopathology and do not attempt to separate Hürthle cell adenomas from Hürthle cell carcinomas on cytology specimens.