Follicular-patterned lesions of the thyroid: the bane of the pathologist.

This review focuses on follicular-patterned lesions of the thyroid gland and their differential diagnosis. Included are a discussion of the features differentiating follicular adenoma from adenomatous or hyperplastic nodule and follicular adenoma from follicular carcinoma and the follicular variant of papillary thyroid carcinoma. The cytologic and histologic characteristics are described, and criteria for diagnosing the major follicular lesions are reviewed.