['To identify clinical predictors of malignancy in patients with intraoperative frozen-section diagnosis of follicular neoplasm of the thyroid.', 'We performed a retrospective cross-sectional study of 71 patients with intraoperative frozen-section diagnosis of follicular neoplasm who underwent thyroidectomy between January 1992 and December 2000. Age, sex, tumor size, and in-office ultrasonography characteristics of the lesions were assessed. These clinical factors were compared between cases that had benign definitive pathologic findings and those that were found to be carcinomas on permanent sections.', 'Nine (13%) of the 71 follicular neoplasms were found to be carcinomas after definitive pathologic evaluation. The incidence of malignancy was 13% (2/16) in men and 13% (7/55) in women (P>.5). Patients younger than 45 years had a 27% (8/30) incidence of malignancy compared with 2% (1/41) in patients 45 years or older (P<.01). Of tumors smaller than 4 cm, 7% (4/55) were ultimately diagnosed as carcinomas compared with 31% (5/16) of those 4 cm or larger (P = .05). When the in-office ultrasonography findings were interpreted as benign, only 7% (3/46) of cases were malignant compared with 40% (4/10) when the ultrasonography findings were suspicious (P = .02).'] Are age , tumor size , and in-office ultrasonography predictive parameters of malignancy in follicular neoplasms of the thyroid?