Cancer of the parathyroid glands.

Hyperfunctioning parathyroid carcinoma is a relatively rare endocrine tumor, accounting for approximately 1% of all cases of primary hyperparathyroidism. The diagnosis is suspected when the tumor is large, parathyroid hormone (iPTH) levels are high, and a palpable tumor is present in the neck. Patients who have recurrence of hyperparathyroidism several months after surgical treatment should be suspected of having a recurrent or persistent parathyroid carcinoma. At operation, a large invasive tumor is usually found. The fibrous, inflammatory-like reaction is the most characteristic indication of malignancy. Even in tumors with minimal invasiveness, the possibility of a carcinoma should be considered if the tumor has mitotic activity and a monotonous instead of a pleomorphic cellular population. If the surgeon can recognize the possibility of parathyroid malignancy and adequately treat the patient during the initial operation, more gratifying results should be obtained.