HYPERCALCEMIA DUE TO PARATHYROID HORMONE-RELATED PROTEIN SECRETION BYMELANOMA

About 1-2% of melanoma patients develop hypercalcemia. We report hyper calcemia without bone metastasis in a 46-year-old woman with advanced melanoma. The hypercalcemia was associated with elevated serum parathy roid hormone-related protein (PTHrP) levels. An even higher concentrat ion (10 times the serum level) in pleural effusion caused by pleural m etastases implied that the source of the increased circulating PTHrP w as the melanoma. Immunohistochemical staining of paraffin sections, pe rformed using a monoclonal antibody (9H7) against the peptide sequence 109-141 of human PTHrP, detected PTHrP in the cytoplasm and nucleoli of melanoma cells in an autopsy specimen but not in specimens from thi s patient prior to onset of hypercalcemia, Considering the evidence, i t is very likely that PTHrP production by melanoma caused hypercalcemi a in this patient.