The Predictive Value of the Fine-Needle Aspiration Diagnosis 'Suspicious for a Follicular Neoplasm, Hürthle Cell Type' in Patients With Hashimoto Thyroiditis

A fine-needle aspiration sample composed exclusively of Hurthle cells is interpreted as “suspicious for a follicular neoplasm, Hurthle cell type” (SFNHCT). Because some nonneoplastic Hurthle cell proliferations in Hashimoto thyroiditis (HT) mimic this cytologic pattern, we examined the positive predictive value (PPV) for malignancy of SFNHCT in patients with HT. Between 1992 and 2007, 401 patients with cytologic findings of SFNHCT were identified at 3 institutions. Histologic follow-up was available for 287 (71.6%), and malignancy was diagnosed in 69 (24.0%). Malignancy was present in 2 (PPV = 9.5%) of 21 patients with HT compared with 67 (PPV = 25.2%) of 266 patients without HT ( P = .081). Although the difference in the rate of malignancy between the HT and non-HT cohorts did not reach statistical significance, the lower risk of malignancy in the HT cohort more closely approximates the risk of cases interpreted as “atypia of undetermined significance.” For this reason, it might be appropriate for Hurthle cell–only aspirates from patients with HT to be categorized as either atypia of undetermined significance or SFNHCT.