Hypercalcaemia due to a calcitriol-producing neuroendocrine tumour

In this case report, we describe a 40-year-old patient with a large grade 2 pancreatic neuroendocrine tumour (pNET) with spleen metastasis. Albeit radical resection, he developed liver metastasis after 2 years, for which he underwent radio frequency ablation and embolization, and was treated successfully with different subsequent lines of systemic therapy. Eight years after the initial diagnosis, he was admitted for symptomatic and refractory hypercalcaemia, due to calcitriol synthesis by the liver metastasis. After tumour load reduction by hemihepatectomy, there was an initial normalization of hypercalcaemia, until it recurred after 18 months. In this period, the liver metastasis had progressed despite chemo- and immunotherapy. Patient underwent an additional extend hemihepatectomy, from which he recovered well with normalization of calcium levels. This case illustrates the hormonal plasticity of pNETs and shows how prolonged survival can be achieved for metastatic pNET by multimodality approach.