['RAS mutations are common in thyroid tumors and confer a high risk of cancer when detected in fine-needle aspiration (FNA) specimens. Specific characteristics of RAS-positive thyroid cancers are not well described.', 'From April 2007 to April 2009, 921 consecutive patients undergoing FNA were evaluated prospectively with a panel of molecular markers. Ultrasonographic, cytological, histological, and surgical outcomes were retrospectively assessed.', 'Sixty-eight aspirates from 66 patients were positive for RAS mutations including 63 cytologically indeterminate (93%), 3 malignant (4%), and 2 benign (3%) specimens. Cancer was histologically confirmed in 52 of 63 aspirates (83%) including the following: 46 papillary thyroid cancers, 4 follicular thyroid cancers, 1 medullary cancer, and 1 anaplastic cancer. All 46 RAS-positive papillary thyroid cancers, including 1 metastatic cancer, had follicular variant histology papillary thyroid cancer; only 11 tumors demonstrated vascular/capsular invasion and 4 had infiltrative growth. Of 48 patients with differentiated thyroid cancer, lymph node metastasis was uncommon and bilateral cancer was present in 48%. Only 33% of malignant nodules were suspicious by preoperative ultrasonography. At a mean follow-up of 22 months, 31 of 35 differentiated thyroid cancer patients (89%) have no evidence of recurrence, 4 patients (9%) have detectable thyroglobulin, 1 patient has bone metastases, and both patients with medullary and anaplastic cancer have died.'] Are rAS mutations in thyroid FNA specimens highly predictive of predominantly low-risk follicular-pattern cancers?