The demise of follicular carcinoma of the thyroid gland.

Over the past several decades, iodide supplementation to food supplies in many parts of the world has been followed by a corresponding decrease in the incidence of follicular thyroid carcinoma. However, pathologists continue to over-diagnose this tumor. Benign lesions (e.g., partly encapsulated hyperplastic nodules, pseudoinvasion after fine needle aspiration), and malignancies (especially the follicular variant of papillary carcinoma) have been misinterpreted as follicular carcinoma. Since the clinical features and biological behavior of true follicular cancer differ from the entities with which it may be confused, it is essential that appropriate histological criteria be applied to the diagnostic interpretation of thyroid nodules that exhibit follicular architecture. Only in this way will it be possible to define prognosis and to evaluate treatment options.