Hürthle cell carcinoma is a better gold standard than Hürthle cell neoplasm for fine-needle aspiration of the thyroid

BACKGROUND: The majority of fine-needle aspirates of the thyroid that demonstrate a predominance of Hürthle cells are diagnosed as suspicious for Hürthle cell neoplasm. Only a minority of these patients are found to have carcinoma at the time of resection. In the current study, an attempt was made to define criteria that were more specific for Hürthle cell carcinoma without a loss in sensitivity. METHODS: The literature was reviewed and 33 aspiration samples diagnosed as suspicious for a Hürthle cell neoplasm (4 nonneoplastic cases, 19 adenoma cases, and 10 carcinomas) were reexamined and reclassified based on criteria derived from the literature. RESULTS: All Hürthle cell carcinomas could be identified using a total of five criteria: predominantly Hürthle cells and scant colloid and at least one of either small cell dysplasia (cytoplasmic diameter less than twice the nuclear diameter, with often quite bland cells), large cell dysplasia (greater than twice the variation in nuclear diameter; large cells typically demonstrate prominent nucleoli and irregular nuclear outlines), crowding (nuclei touching), and dyshesion (single cells). Three of 4 nonneoplastic aspiration samples (75%) and 7 of 19 Hürthle cell adenomas (37%) did not meet these criteria and could reliably be diagnosed as benign. CONCLUSIONS: By focusing on criteria for Hürthle cell carcinoma rather than all Hürthle cell neoplasms, criteria can be developed that improve the specificity without a loss of sensitivity.