Distinguishing features of primary hyperparathyroidism in patients with breast cancer.

Thirty-five women with breast cancer and primary hyperparathyroidism (1 degree HPT) were admitted to Memorial Hospital during a 25-year period. The incidence of primary hyperparathyroidism in the breast cancer patients was similar to the incidence in the total patient population at Memorial Sloan-Kettering Cancer Center (0.15% and 0.14%, respectively). The patients with 1 degree HPT disease had clinical findings which distinguished them from those patients with cancer-related hypercalcemia. Eighty percent of the breast cancer patients with primary hyperparathyroidism had earlier stage disease (Stage 0, Stage 1, Stage 2); whereas 97% of the patients with breast cancer and hypercalcemia (not due to 1 degree HPT) had advanced disease. There appeared to be a trend towards improved survival in the breast cancer patients with primary hyperparathyroidism when compared to patients of similar stage of disease who did not have parathyroid disease.