A focal nodular Hürthle cell hyperplasia in Hashimoto's thyroiditis: A diagnostic dilemma on fine needle aspiration.

Hürthle cells are seen in a variety of nonneoplastic and neoplastic thyroid gland lesions. Number and morphology of Hürthle cell vary in thyroid aspirate. Occasionally, thyroid aspirate in focal nodular Hürthle cell hyperplasia in Hashimoto's thyroiditis exclusively comprise of Hürthle cells and mimics Hürthle cell neoplasm. Fine needle aspiration (FNA) diagnosis in such cases is challenging. A 60-year-old female presented with goiter and clinical features of hyperthyroidism. FNA smears showed Hürthle cells arranged in flat sheets and lying singly with occasional lymphocytes in Hürthle cell sheets. Repeat aspiration from other site showed lymphocytes, infiltrating the thyroid follicular cells. We conclude that a careful search of lymphocytes in Hürthle cell sheets in cytology smears, multiple aspirates, associated clinical findings and ancillary techniques reduce the diagnostic pitfall and avoid unnecessary surgery.