Recognizing the Limitations and Pitfalls of Cytology for Anaplastic Carcinoma within Hürthle Cell (Oncocytic) Carcinomas

Abstract

Fine needle aspiration is an initial method for diagnosis of enlarged thyroid nodules. Hurthle cell neoplasm is usually cytomorphologically distinct from undifferentiated/anaplastic thyroid carcinoma, except when there is marked atypia. Herein we contrast two cases, highlighting Hurthle cell atypia mimicking anaplastic change versus true anaplastic thyroid carcinoma. The first case is of a 44 year old female with a rapidly enlarging thyroid mass presenting with an outside fine needle aspiration diagnosis of anaplastic thyroid carcinoma; however the thyroidectomy found only a Hurthle cell follicular carcinoma with a component of cytologic atypia. The second case is from an 81 year old female with acute onset neck swelling. The cytologic evaluation was suspicious for a Hurthle cell neoplasm only, while the thyroidectomy showed Hurthle cell follicular carcinoma with anaplastic thyroid carcinoma. Hurthle cell neoplasm may have marked atypia, for which anaplastic thyroid carcinoma is important to exclude. Since fine needle aspirations have sampling limitations, subsequent surgical excision is essential in determining the correct diagnosis in cases of cytologic Hurthle cell neoplasm which may harbor anaplastic thyroid carcinoma.