Follicular-patterned afflictions of the thyroid gland: reappraisal of the most discussed entity in endocrine pathology.

The past 25 years has seen a marked increase in our understanding of thyroid neoplasia, from the interrelationship with radiation exposure, the definition of variants of papillary carcinoma, to the application of molecular biology techniques to capture a more basic definition of tumor development, diagnosis, and prognostic implications. No other group of thyroid tumors has been studied as much as those with follicular pattern. In this review, we present a reappraisal of these controversial lesions in light of the issues with the diagnostic problems and classification schemes of follicular thyroid lesions, with emphasis on the progress made in the past quarter century and a focus on the current persistent controversies.