Oncocytic variant of papillary thyroid carcinoma associated with Hashimoto's thyroiditis: a case report and review of the literature.

Identification of Hürthle cells on fine-needle aspiration (FNA) of the thyroid leads to a wide differential diagnosis including benignand malignant entities. We report the cytological and histological findings of a patient with an oncocytic variant of papillary thyroid carcinoma (PTC) with concurrent Hashimoto's thyroiditis. FNA revealed a lymphoplasmacytic infiltrate with Hürthle cells demonstrating abnormal chromatin patterns, nuclear enlargement, pleomorphism, intranuclear cytoplasmic invaginations, and foci of papillary aggregates. Because of the degree of nuclear atypia and suspicion for concurrent papillary thyroid carcinoma, a total thyroidectomy was performed revealing a papillary arrangement of Hürthle cells with classic PTC nuclear changes and associated Hashimoto's thyroiditis. This report discusses cytopathological features of a rare variant of PTC (oncocytic subtype) in the background of Hashimoto's thyroiditis. We also briefly discuss the differential diagnosis and diagnostic pitfalls of Hürthle cell lesions, with a review of the literature.