Somatostatin receptor expression in a parathyroid hormone-related peptide-secreting pancreatic neuroendocrine tumour causing severe hypercalcaemia

Abstract

Humoral hypercalcaemia is a common complication of malignancy with parathyroid hormone-related protein (PTHrP) as a major cause. Breast and lung cancer are relatively common sources of ectopic PTHrP secretion leading to increased osteoclastic bone resorption. We report the rare case of a 40-year-old man with severe hypercalcaemia due to a PTHrP-secreting poorly differentiated endocrine carcinoma of the pancreas. On immunohistochemistry, the tumour was positive for PTHrP and somatostatin receptors sst1, sst2, and sst3, whereas sst4 and sst5 were not detected. We demonstrate the transient improvement of hypercalcaemia after adding octreotide to the treatment mainstays in hypercalcaemia of malignancy (fluid repletion, administration of bisphosphonates, loop diuretics, and glucocorticoids). To the best of our knowledge, this is the first report showing somatostatin receptor expression in a PTHrP-secreting pancreatic neuroendocrine tumour.