WHAT IF MANY FOLLICULAR VARIANT PAPILLARY THYROID CARCINOMAS ARE NOT MALIGNANT? A REVIEW OF FOLLICULAR VARIANT PAPILLARY THYROID CARCINOMA AND A PROPOSAL FOR A NEW CLASSIFICATION

Objectives: To review the relevant literature concerning follicular variant of papillary thyroid carcinoma (FVPTC) with an emphasis on the heterogeneity of this disorder and to propose a new classification for FVPTC on the basis of molecular diagnostics and apply the classification to a typical case. Methods: English-language articles pertaining to FVPTC published between January 1990 and December 2010 were reviewed. Results: FVPTC is particularly vexing. The criteria for diagnosing FVPTC appear to have changed over the years. Pathologists often disagree about the diagnosis of FVPTC. The clinical behavior of these tumors is variable. Molecular diagnostic studies suggest that FVPTC represents a heterogeneous group of disorders rather than a single entity. Conclusions: On the basis of the available data, it is proposed that individual cases of FVPTC be reclassified as papillary thyroid carcinoma, follicular thyroid carcinoma, or follicular adenomas, after appropriate molecular biologic studies have been completed. Long-term follow-up studies to validate this classification are necessary. (Endocr Pract. 2011;17:768-787)