They are often larger than those typically seen in adenomas and have a bland cytologic appearance. The parenchyma may appear indistinguishable from a benign adenoma. The most reliable histologic finding in carcinoma is extracapsular invasion by the tumor, but this is seen in only two-thirds of cases. Some degree of nuclear atypia is commonly seen, and mitotic figures are usually evident. There is no effective medical therapy for parathyroid carcinoma.
Patients often present with severe hypercalcemia that initially requires medical management.
However, hypercalcemia due to parathyroid cancer is often resistant to long-term medical management and is usually the cause of death in patients with metastatic disease. Because the hypercalcemia caused by parathyroid cancer is often severe, preoperative medical intervention to control hypercalcemia is often required. Volume expansion with normal saline and diuresis with furosemide is often adequate. Take care to ensure that any volume contraction is corrected before the operation. The goal of the initial operation is to remove the tumor en bloc with any adherent tissue, the ipsilateral thyroid lobe, and any enlarged lymph nodes.