Hürthle cell and mitochondrion-rich cell tumors. A clinicopathologic study.

Hürthle cells are large eosinophilic thyroid cells that contain a large number of mitochondria with a high content of oxidative enzymes. In the last 10 years several reports have emphasized the disagreement over the morphologic features, biologic behavior and treatment of Hürthle cell tumors. The authors reviewed the clinical and pathologic features of 28 patients with Hürthle cell and mitochondrion-rich cell tumors (16 adenomas, 10 follicular carcinomas, and 2 papillary carcinomas) and present electron microscopic, immunohistochemical, and morphometric data. The results suggest that there is a correlation between biologic behavior and pathologic findings, that tumor size should not be considered a special conditioning factor in order to assign a biologic behavior, that nuclear size and anisokaryosis are not an absolute criteria for diagnosing malignancy, and finally, that electron microscopic examination is not useful in separating benign from malignant Hürthle cell tumors.