Carcinoma of the breast associated with hypercalcemia and the presence of parathyroid hormone-like substances in the tumor.

A woman with metastatic carcinoma of the breast developed hypercalcemia 39 months after mastectomy. The hypercalcemia remitted after treatment but recurred 12 months later, accompanied by elevated levels of serum immunoreactive parathyroid hormone (PTH). A urea/HC1 extract of hepatic metastases contained immunoreactive PTH, material which stimulated the resorption of fetal rat bone in tissue culture, and material which stimulated chick renal adenylate cyclase activity. These findings strongly suggest that this breast cancer produced a PTH-like substance.