Diminishing diagnosis of follicular thyroid carcinoma

Follicular carcinomas have been reported as 10% to 15% of thyroid malignancies. Refinements in the histologic criteria applied in the classification of follicular lesions have occurred. We aim to document the true incidence of follicular cancers in a cohort from a high-volume endocrine practice.

Patient charts were reviewed and cancers were classified into major subtypes; papillary cancers were further classified by common variants. Proportions were compared to historic Surveillance, Epidemiology, and End Results (SEER) database proportions.

Only 2.7% of patients had follicular carcinoma. The proportion of patients with follicular cancer was less than the reported rates of 10% to 15%, and less than the 6.7% extrapolated from SEER.

The proportion of follicular cancers is less than traditionally reported. This change is due to an increased incidence of papillary cancers, and modifications of the histologic criteria used for classification of encapsulated follicular lesions. There are potential prognostic consequences, as follicular cancers have been perceived as more aggressive.