title: Sporadic diffuse segmental interstitial cell of Cajal hyperplasia harbouring two gastric gastrointestinal stromal tumours (GIST) mimicking hereditary GIST syndromes.
abstract: BACKGROUND
  Gastrointestinal stromal tumours (GISTs) are thought to derive from or differentiate towards the interstitial cells of Cajal (ICC) as most demonstrate a similar immunoprofile: CD117+, CD34+ and DOG1+. ICC hyperplasia refers to KIT-expressing microscopic spindle cell proliferations involving the myenteric plexus.
  
  
  METHODS
  74 year-old male presented with a 5-year history of heartburn and dysphagia. Imaging revealed a 4cm GIST in the gastric fundus. Pathology of the resected specimen revealed diffuse segmental ICC hyperplasia harbouring two macroscopic GISTs and a 'tumorlet'. A mutation in c-KIT exon 11 was detected in both the solid and the diffuse components.
  
  
  CONCLUSIONS
  ICC hyperplasia can occur either as a sporadic focal lesion or in a syndromic setting, known to predispose to multiple GIST tumours at different sites. The majority of cases of sporadic ICC hyperplasia previously reported were of localised type. The hereditary form is mostly caused by germline mutations in c-KIT and PDGFRA or in patients with NF-1 andpresents as a diffuse hyperplasia, usually with a confluent, nodular or multifocal growth pattern.
  
  
  CONCLUSIONS
  We describe a diffuse form of sporadic ICC hyperplasia harbouring multifocal GISTs, mimicking diffuse ICC hyperplasia in hereditary GIST syndromes. Detection of somatic c-KIT exon 11 mutation ruled out a hereditary disorder.
authors.affiliation: Department of Surgery, The London Clinic, 116 Harley Street, London W1G 7JL, United Kingdom; Department of Academic Surgery, The Royal Marsden NHS Foundation Trust, Fulham Road, London SW3 6JJ, United Kingdom. Electronic address: mafaldajardim@hotmail.com.
authors.forename: Mafalda Costa
authors.initials: MC
authors.lastname: Neves
authors.affiliation: Department of Pathology, The London Clinic, 116 Harley Street, London W1G 7JL, United Kingdom; Section of Investigative Medicine, Division of Diabetes, Endocrinology & Metabolism, Faculty of Medicine, Imperial College, South Kensington, London SW7 2AZ, United Kingdom. Electronic address: g.stamp@imperial.ac.uk.
authors.forename: Gordon
authors.initials: G
authors.lastname: Stamp
authors.affiliation: Department of Surgery, The London Clinic, 116 Harley Street, London W1G 7JL, United Kingdom; Department of Academic Surgery, The Royal Marsden NHS Foundation Trust, Fulham Road, London SW3 6JJ, United Kingdom; Department of Surgery and Cancer, Faculty of Medicine, Imperial College, South Kensington, London SW7 2AZ, United Kingdom. Electronic address: Satvinder.Mudan@rmh.nhs.uk.
authors.forename: Satvinder
authors.initials: S
authors.lastname: Mudan
keywords: Gastrointestinal stromal tumors; Hyperplasia; Interstitial cells of Cajal