Parathyroid hormone-related protein and hypercalcemia in patients with metastatic melanoma: case report and review

Hypercalcemia associated with malignancy has been attributed to osteolytic processes secondary to bony metastases and to humoral factors causing increased bone resorption and decreased renal excretion of calcium. Parathyroid hormone-related protein (PTH-rP) is a humoral factor that has been associated with hypercalcemia in renal cell carcinoma, squamous cell carcinoma, and bladder carcinoma. Hypercalcemia does occur in patients with melanoma; however, few studies have reported on hypercalcemia in these patients, and even fewer have described a direct connection to PTH-rP. We here report a patient with stage IV malignant melanoma presenting with severe hypercalcemia associated with elevated PTH-rP levels. Immunohistochemistry showed strong expression of PTH-rP in biopsy of the patient's subcutaneous masses. In addition, we found a 4.9% incidence of hypercalcemia in 1,146 consecutive patients treated for metastatic melanoma at the Surgery Branch of the National Cancer Institute between January 1, 1988 and March 31, 2000. Thus, PTH-rP may play a significant role in severe hypercalcemia in patients with metastatic melanoma. The discovery of PTH-rP and relevant literature will also be reviewed.