A Patient in Whom One Pathologist Says She Has Cancer, and Another Says that the Lesion Is Benign

Abstract

Follicular adenoma and minimally invasive follicular carcinoma are thyroid neoplasms that share many clinical and pathologic characteristics. The distinction between them is crucial, however, because while follicular adenoma is entirely benign and requires no additional treatment, follicular carcinoma possesses the capacity for aggressive behavior and, as a result, is usually treated with completion thyroidectomy and subsequent radioactive iodine. While the criteria for distinguishing the two tumors are seemingly straightforward, there are many subtleties and pitfalls in interpreting follicular thyroid neoplasms, as the experienced surgical pathologist knows all too well. Due to the significance of resolving the differential diagnosis between follicular adenoma and follicular carcinoma, if any doubt persists after ample tissue sampling and extensive evaluation of a tumor, a second opinion from an expert in thyroid pathology can be an invaluable resource.