NG and TH have research fellowships sponsored by Ipsen, Ettlingen and the Hensel Stiftung, Kiel, Germany

NG and TH have research fellowships sponsored by Ipsen, Ettlingen and the Hensel Stiftung, Kiel, Germany. Competing interests: None.. neuroendocrine tumours (NETs) were gastrin\producing tumours; 13/28 (46.4%) revealed LOH on 11q13 and/or C11. Five of the NETs were somatostatin\expressing tumours, two revealing LOH. Allelic loss was detected in tumours as small as 300?m (gastrin) and 400?m (somatostatin) in diameter. The gastrin\producing tumours showed different deletion/retention patterns. Hyperplastic somatostatin cell lesions, similar to those of the gastrin cells, were present in all patients. The hyperplastic lesions of both cell lines consistently retained both 11q13 alleles. Conclusions Allelic deletion of the gene may reflect a pivotal event in the development of multifocal gastrin and somatostatin cell neoplasms in the duodenum of patients with MEN1. The observation of distinct deletion patterns in small synchronous tumours supports the concept that each gastrin\producing tumour in an individual MEN1 patient arises from an independent cell clone. Duodenal gastrinomas may occur sporadically or in the setting of the multiple endocrine neoplasia type 1 (MEN1) syndrome. Sporadic and MEN1\associated duodenal gastrinomas differ in their Benfotiamine biological behaviour. Although sporadic gastrinomas are solitary tumours, MEN1\associated gastrinomas are usually multicentric.1,2,3,4 Recently, it was shown Benfotiamine that duodenal gastrinomas in patients with MEN1 are associated with diffuse hyperplastic gastrin cell changes and multicentric gastrin\producing microtumours 1?mm in size within the grossly unaffected duodenal mucosa. It was concluded that these microscopic lesions precede the development of MEN1\associated gastrinomas.4 The vast majority of patients with MEN1 display heterozygotic germline mutations of the gene.5,6 According to Knudson’s two\hit hypothesis for tumour suppressor genes, the development of MEN1\related tumours is associated with somatic inactivation of the wild\type allele on chromosome 11q13.5,7,8,9,10,11,12,13,14 Recently, Benfotiamine a loss of heterozygosity (LOH) at 11q13 was demonstrated in pancreatic microadenomas of patients with MEN1 and interpreted as a very early event in MEN1\related pancreatic tumorigenesis.15 We do not know at present at what stage a similar change occurs in MEN1\related duodenal neuroendocrine tumours (NETs). If deletion of the wild\type allele of the gene is also an early step in gastrinoma development, LOH would represent a decisive molecular event discriminating between hyperplastic and early neoplastic lesions. To date, PCR\based LOH analysis and fluorescence in situ hybridisation (FISH) analysis of macrotumours have been used to examine defined chromosome loci in hereditary and non\hereditary duodenopancreatic NETs.9,12,14,16,17,18,19 However, these techniques are less than optimal for analysing scattered hormone\expressing cellsfor example, in the diffuse endocrine system of the gut. To Benfotiamine analyse the occurrence and frequency of LOH on chromosome 11q13 in duodenal MEN1\related microtumours, hyperplastic lesions and duodenal neuroendocrine cells, we established a combined FISH/immunofluorescence method, enabling us to analyse allelic deletions and hormone expression in duodenal neuroendocrine cells at the same time. In addition to LOH analysis, we examined whether the MEN1\related changes in the duodenum are restricted to the gastrin cell lineage or additionally involve somatostatin cells, because sporadic somatostatin\producing tumours are second in frequency among all NETs of the duodenum,20,21 and have been described in association with the MEN1 syndrome.22 Materials and methods Patients The study included six patients with MEN1 having duodenal gastrinomas and ZollingerCEllison syndrome (ZES; three men and three women; mean age 43?years; range 33C54?years at the time of operation), whose specimens were FHF4 collected between 1980 and 2005 in the consultation files and NET archives of the Departments of Pathology of the Universities Benfotiamine of Kiel (Kiel, Germany) and Zrich (Zrich, Switzerland). Four of these patients were included in earlier studies investigating the histopathology of duodenal gastrinomas and pancreatic endocrine tumours in MEN1.1,4,23 The diagnosis of ZES was established on the basis of clinical symptoms: an increased fasting serum gastrin level ( 125?pg/ml) combined with a low pH in the fluid of the stomach and a positive secretin\stimulation test (increase of serum gastrin concentration to 200?pg/ml). Since none of the patients had a somatostatinoma syndrome, SOM levels were not determined. All patients fulfilled the.