Benign breast dysplasia causing hypercalcemia.

An adolescent female had hypercalcemia and massive, bilateral breast enlargement. At neck and mediastinal explorations three parathyroid glands were removed and found to be histologically normal. Following bilateral mastectomy the hypercalcemia resolved within two days and did not recur during a six-year period of followup. Microscopic examination of the excised breast tissue revealed marked dysplasia but no cancer. Those findings suggest that benign, dysplastic breast tissue can release humoral mediators of hypercalcemia.