Somatostatin-Immunoreactive Pancreaticoduodenal Neuroendocrine Neoplasms: Twenty-Three Cases Evaluated according to the WHO 2010 Classification

Neuroendocrine neoplasms of the pancreas and duodenum with predominant or exclusive immunoreactivity for somatostatin (pdSOMs) are rare, and knowledge about tumour biology, treatment, survival and prognostic factors is limited. This study aims to describe clinical, pathological and biochemical features as well as treatment and prognosis of pdSOMs.

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

Among the 9 patients with duodenal SOM, the male/female ratio was 4/5. All males and 1 female had neurofibromatosis type 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 the patients with 2B disease. Of the 14 patients with pancreatic SOM or an unknown primary tumour, the male/female ratio was 2/12. One male had multiple endocrine neoplasia type 1. Five had stage 1A/2B and 9 had stage 4. The Ki-67 index was 1-40% (median 7%). Plasma somatostatin was elevated in 7 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 significantly poorer survival.

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