Afirma GEC and thyroid lesions: An institutional experience.

BACKGROUND: Thyroid fine-needle aspiration (FNA) is used to assess appropriate management of nodular thyroid lesions safely, but Bethesda category III (atypia of undetermined significance/follicular lesion of undetermined significance) and category IV (follicular neoplasm/suspicious for follicular neoplasm) lesions are problematic. This study aimed to evaluate the Afirma Gene Expression Classifier (GEC) results for lesions in those categories.

METHODS: Medical records of patients with thyroid FNA and GEC results were obtained from archived material. Results were compared to thyroidectomy histologic diagnoses.

RESULTS: Among 66 patients with FNA results (47 women and 19 men aged 26-89 years [mean, 59.4 years]), surgical reports were available for 38. Afirma GEC results were "nondiagnostic" for 10 of 66 (15.2%), "benign" for 22 (33.3%), and "suspicious" for 34 (51.5%). Surgical diagnosis was available for 38 of 66 patients (57.6%); GEC results for 6 (15.8%) of these were "nondiagnostic," 27 (71.0%) were "suspicious," and 5 (13.2%) were "benign." One of 6 (16.7%) samples with "nondiagnostic" results, 1 of 5 (20%) with "benign" results, and 15 of 27 (55.6%) with "suspicious" results were malignant on histology. Papillary carcinoma was the most common tumor type (15 of 38; 39.5%).

CONCLUSIONS: Afirma GEC results minimize the number of unnecessary operations. Afirma GEC testing may be reserved for FNAs with a category III diagnosis on follow-up cytologic examination. We recommend a conservative approach for "suspicious" Afirma GEC results if Hürthle cells are seen with FNA.