A Case of Leiomyosarcoma Associated with Humoral Hypercalcemia of Malignancy: Demonstration of Biological and Immunological Activities of Parathyroid Hormone‐related Protein in the Tumor Extract

Hypercalcemia occurred in a patient with leiomyosarcoma when multiple lung metastases developed. Despite normal plasma parathyroid hormone (PTH) levels and low 1,25‐dihydroxyvitamin D, this hypercalcemic patient had a marked hypercakiuria and phosphatnria associated with an increased excretion of nephrogenous cyclic AMP (NcAMP). Administration of cisplatin ameliorated both the hypercalcemia and hypercalciuria without any reduction in tumor size or NcAMP excretion. Terminally, acute pancreatitis occurred producing a profound hypocalcemia. In the extract of tumor tissue obtained post mortem, bioactivity stimulating the generation of cyclic AMP in osteogenic cells was demonstrated along with the immunoreactive PTH‐related protein (PTH‐rP). This is the first report of a solid non‐epithelial malignancy producing PTH‐rP and associated with humoral hypercalcemia of malignancy. The hypercalcemia in this case caused acute pancreatitis, which led to a profound hypocalcemia