Follicular Neoplasm/Suspicious for a Follicular Neoplasm

Abstract

There has been great variability in the way thyroid aspirates that are suspicious for a follicular neoplasm have been reported, as demonstrated by a review of the literature compiled for the NCI-sponsored State of the Science Conference in 2007. The terminology used has ranged from broad terms like “follicular lesion,” “follicular proliferation,” and “indeterminate” to the more specific terms like “rule out/suggestive of/suspicious for follicular neoplasm” to the definitive “follicular neoplasm.” Much of this variability results from the fact that the so-called “follicular lesions,” comprised of nodular goiter (nodular hyperplasia), follicular adenoma, and follicular carcinoma, have overlapping cytomorphologic features and cannot be accurately distinguished by fine needle aspiration (FNA) alone. Nevertheless, certain cytologic features are very useful in raising the possibility of a neoplasm, most importantly the possibility of a follicular carcinoma. In this regard, FNA can be considered a screening test, selecting for surgery those nodules with a greater probability of malignancy. The final diagnosis depends upon lobectomy because capsular and/or vascular invasion are the sine qua non of follicular carcinoma.