Hypercalcemia from metastatic pancreatic neuroendocrine tumor secreting 1,25-dihydroxyvitamin D

Malignant hypercalcemia occurs in about 20-30% of patients with cancer, both solid tumors and hematologic malignancies. The secretion of parathyroid hormone-related protein (PTH-rP) is the most common cause and has been shown to be the etiology of hypercalcemia associated with neuroendocrine tumors. Here we report the case of a patient with metastatic pancreatic neuroendocrine tumor who developed hypercalcemia more than 4 years after the initial diagnosis as a result of secretion of 1,25-dihydroxyvitamin D, a mechanism only commonly seen in lymphomas. The successful control of the patient’s disease with capecitabine and temozolomide led to the alleviation of this paraneoplastic syndrome.