Production of bone resorbing activity in poorly differentiated monocytic malignancy.

A patient with poorly differentiated monocytic malignancy had extensive lytic lesions of bone and hypercalcemia. The patient's bone margins showed little evidence of osteoclast activity. Serum parathormone concentrations were slightly increased relative to the degree of hypercalcemia, consistent with impaired renal function. Serum concentrations of the relevant prostaglandins were normal. Supernatant medium from cultured tumor cells caused prominent bone resorption in vitro. The studies on this patient provide evidence that malignant cells of the monocyte-macrophage line are capable of direct bone resorption.