Hypercalcemia in patients with breast cancer. Osseous metastases, hyperplastic parathyroid tissue, or pseudohyperparathyroidism?

Breast cancer is the malignant neoplasm most commonly associated with hypercalcemia. At the University of Texas M. D. Anderson Hospital, Houston, during the fiscal year 1977 to 1978, of 16,887 patients having calcium determinations, 7.8% had hypercalcemia. From 1969 to 1979, 13 patients had proved and three had presumed primary hyperparathyroidism associated with breast cancer. Two other patients had pseudohyperparathyroidism. Selective neck vein catheterization was used in 17 of the 18 patients and helped localize and confirm the diagnosis of primary hyperparathyroidism. Chloride-phosphate ratios were elevated in 13 of the 14 patients with proved or presumed primary hyperparathyroidism. This condition may mimic osseous metastases by producing brown tumors or compression fractures. In patients with breast cancer and hypercalcemia, particularly without osseous metastases, a careful diagnostic evaluation is warranted to rule out primary hyperparathyroidism.