Endocrine Abstracts

Pancreatic Neuroendocrine tumours, P-NETs, comprise 2–3% of all pancreatic tumours. Usually classified as functional or non-functional based on whether these secrete biologically active amines, causing specific syndromes or not. Even non-functional P-NETs in majority of cases secrete substances, not associated with any specific syndrome, like Chromogranin A and Chromogranin B and Pancreatic Polypeptide (PP). An estimated 2% of all the neuroendocrine tumours secrete Pancreatic Polypeptide exclusively and are sometimes called PPomas. This is a rare group of NETs and in almost all the reported cases, the source, usually a tumour, was originating from the pancreas.

The case we describe is unique as the source of excess PP is neither coming from the pancreas nor the intestine. This 65-year old gentleman with background of type 2 DM presented initially with a few weeks’ history of explosive diarrhoea with no flushing, pruritus or other symptoms usually associated with carcinoid syndrome. CT scan showed a soft tissue mass with calcifications close to the mesentery at the level of the lower poles of kidneys. A full biochemical profile for work up of neuroendocrine tumour was carried out showing raised Chromogranin A (364 pmol/l) and B (282 pmol/l) and PP levels (>500 pmol/l) with rest of profile unremarkable (Gastrin 6 pmol/l, Glucagon 25 pmol/l, Somatostatin 51 pmol/l, VIP 10 pmol/l and 24 hour urine 5HIAA 67 umol/24 hour). The mass was confirmed as somatostatin avid lesion with no uptake elsewhere on Octreotide scan. Patient was referred to neuroendocrine oncologist for further management.

A thorough literature search has not shown previously reported extra-pancreatic PPoma causing diarrhoea. Usually PPomas are considered silent but we believe this is no longer true and can arise even from outside pancreas. This case highlights that we should continue to have a high index suspicion of a functional NET even if GUT hormones and 5HIAA are normal.

Keywords: PPoma; Extra-pancreatic; Extra-intestinal