Hürthle Cell Lesions

Abstract

Hurthle cell changes are frequently seen in reactive/hyperplastic conditions and can be extensive, resulting in the formation of nodules that must be distinguished from their neoplastic counterparts, Hurthle cell adenomas and Hurthle cell carcinoma. The primary goal of thyroid FNA in the management of Hurthle cell nodules is to separate those for which surgery is indicated, i.e., Hurthle cell adenomas and carcinomas, from those that can be managed conservatively, i.e., adenomatous nodules with oncocytic changes and Hashimoto’s thyroiditis. The distinction between Hurthle cell adenomas and carcinomas is not possible on cytology because of the inability of cytology to establish the presence of capsular and/or vascular invasion. Therefore, rendering a diagnosis of Hurthle cell neoplasm implies that these lesions should be excised to exclude a malignancy. The criteria for diagnosing “follicular neoplasm, Hurthle cell type,” or “suspicious for a follicular neoplasm, Hurthle cell type” are moderately to markedly cellular aspirate that consists exclusively or predominantly (>75 %) of Hurthle cells with little or no colloid and lack of background lymphocytes. The Hurthle cells can be either small with high N/C ratio (≥50 %) (small cell dysplasia) or large with at least 2× variability in nuclear size (large cell dysplasia). The differential diagnosis includes other neoplasms such as oncocytic and tall cell variants of papillary thyroid carcinoma, medullary carcinoma, parathyroid adenoma, and metastatic renal cell carcinoma.