Follicular neoplasms of the thyroid are usually diagnosed following fine-needle aspiration (FNA) biopsy of a dominant thyroid nodule. An FNA diagnosis of a follicular neoplasm represents a heterogeneous group of lesions including benign follicular hyperplasia, follicular adenomas, follicular carcinomas, and the follicular variant of papillary carcinoma. Hürthle cell neoplasms are also often included in this group. Because the criteria for malignancy in both follicular and Hürthle cell neoplasms requires vascular or capsular invasion seen on permanent histology, the majority of these patients undergo surgical resection. Intraoperative frozen section analysis of follicular neoplasms rarely renders informative information. Approximately 20% of these lesions prove to be malignant and for lesions greater than 1.0 cm in size, the majority of surgeons and endocrinologists recommend a total thyroidectomy. Postoperative treatment generally includes therapeutic doses of 131I for follicular carcinomas.