OBJECTIVE: Neuroendocrine neoplasms in the pancreas and duodenum with predominant or exclusive immunoreactivity for somatostatin (p-dSOMs) are rare, and knowledge on tumour biology, treatment, survival and prognostic factors is limited. This study aimes to describe clinical, pathological, and biochemical features as well as treatment and prognosis.

DESIGN: Twenty-three patients with p-dSOM (9 duodenal, 12 pancreatic, 2 unknown primary tumour) were identified from our prospective neuroendocrine tumour (NET) database, and data according to the study aims were recorded.

RESULTS: Of the 9 patients with duodenal SOM the m/f ratio was 4/5. All males and one female had NF-1. Seven patients had stage 1A-B and 2 had stage 2B disease. The Ki-67 index was 1-5% (median 2%). Plasma somatostatin was elevated in patients with 2B disease. Of the 14 patients with pancreatic SOM or unknown primary tumour the m/f ratio was 2/12. One male had MEN-1. Five had stage 1A-2B and nine had stage 4. The Ki-67 index was 1-40% (median 7%). Plasma somatostatin was elevated in seven patients. Patients reported symptoms related to the somatostatinoma syndrome, but none fulfilled the criteria for a full syndrome. Primary tumour in the pancreas, metastatic disease at diagnosis and higher tumour grade were all associated with a significantly poorer survival.

CONCLUSION: None of the patients with p-dSOM presented with the full somatostatinoma syndrome. Prognostic factors are localisation of the primary tumour, dissemination and tumour grade. A Ki-67 of 5% may discriminate the course of disease.