Hypercalcemia induced by parathyroid hormone-related protein from lung cancer tissue.

Most lung carcinomas with hypercalcemia are usually unresectable. However, this case was resectable and the serum calcium level was normalized after the operation. Messenger RNA of the precursor of PTH-related protein (PTHrP), a substance that may be one of the causes of hypercalcemia in malignant neoplasms, was identified in the tumor tissue of the patient. The patient was a 60-year-old man with squamous cell carcinoma originating from the posterior basal segment of the left lung and invading the main bronchus and left atrium. The serum calcium level was 14.3 mg/dl, preoperatively. Pneumonectomy with partial left atrium resection was carried out and the serum calcium level became normal postoperatively. Three months following the operation, this measurement was 9.4 mg/dl, but increased to 16.2 mg/dl at four months, at which time he experienced lumbago and chest pain. The patient died eight months following the operation from uncontrollable renal failure. In the tumor tissue, mRNA of PTHrP precursor was identified. To our knowledge, this is the first case of lung cancer that could be resected, and in which PTHrP was found present.