Intranuclear cytoplasmic invaginations in a Hürthle-cell carcinoma of the thyroid

According to the literature, the finding of intranuclear cytoplasmic invaginations in fine needle aspiration biopsies from thyroid tumors is indicative of a papillary thyroid carcinoma. A case is presented in which the aspiration specimen showed marked intranuclear cytoplasmic invaginations from a tumor that histologically was a Hürthle-cell (oncocytic) carcinoma with a trabecular pattern. The classification of thyroid carcinomas and the significance of intranuclear cytoplasmic invaginations as a criterion for thyroid malignancy are discussed.