Metastatic neuroendocrine tumor of unknown primary presenting as acute pancreatitis

Neuroendocrine tumors of unknown primary site are rare. Among all the tumors of unknown primary, neuroendocrine tumors account for less than 5% of such cases. They are identified by immunohistochemical staining which is strongly positive for chromogranin, synaptophysin, or electron microscopy identification of neurosecretory granules. We present a case of metastatic poorly differentiated neuroendocrine tumor with no identifiable primary, presenting as acute pancreatitis, hypercalcemia, and disseminated bony metastasis. Such presentation has been rarely reported before. Although the nature of these tumors remains undefined, the diagnosis of poorly differentiated neuroendocrine carcinoma identifies a potentially treatable subgroup.