Follicular thyroid carcinoma

Follicular thyroid carcinoma is being diagnosed less and less frequently despite the increasing incidenceof well-differentiated thyroid carcinomas everywhere. This review will discuss the reasons underlying suchan observation focusing on the evolution of the morphological and immunohistochemical diagnostic criteriaof follicular thyroid tumors. It will address the differential diagnosis between follicular carcinoma andthree tumor types—follicular adenoma, follicular variant of papillary carcinoma and poorly differentiatedcarcinoma—as well as the problems raised by the newly described categories of follicular tumors: folliculartumor of uncertain malignant potential, well-differentiated tumor of uncertain malignant potential and well-differentiated carcinoma, not otherwise specified. Finally, the prognostic and therapeutic significance of somepromising molecular biomarkers will be discussed within the frame of the aforementioned histopathologicalclassification.Modern Pathology (2011) 24, S10–S18; doi:10.1038/modpathol.2010.133Keywords: diagnosis; follicular thyroid carcinoma; molecular biomarkers; prognosis