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Int J Clin Exp Pathol 2010;3(5):549-556

Case Report
Sporadic segmental Interstitial cell of cajal hyperplasia (microscopic GIST) with unusual
diffuse longitudinal growth replacing the muscularis propria: differential diagnosis to
hereditary GIST syndromes

Abbas Agaimy, Bruno Märkl, Hans Arnholdt, Arndt Hartmann, Regine Schneider-Stock, Runjan Chetty

Institute of Pathology, University Hospital, Erlangen, Germany; Institute of Pathology, Klinikum Augsburg, Augsburg, Germany; Department of
Pathology, University of Glasgow, Glasgow, Scotland.

Received May 11, 2010, accepted May 22, 2010, available online May 31, 2010

Abstract: Gastrointestinal stromal tumors (GIST) usually form a well-circumscribed mass. However, patients with germline mutations in c-KIT,
PDGFRA and NF1 may present with diffuse interstitial cell of Cajal (ICC) hyperplasia along the Auerbach plexus without forming a discrete
mass. To our knowledge, sporadic diffuse ICC hyperplasia replacing the gut wall has not been described previously. We describe herein two
such cases. Case 1 was a 59-yr-old woman who presented with signs of ileus and a large mass submitted as Meckel diverticulum. The
resection specimen showed a large GIST with diverticulum-like and solid areas. The diverticular component showed a diffuse proliferation of
spindle cells extending for several centimetres from the solid tumor replacing the full thickness of the gut wall and lined by intact mucosa.
Mutation analysis revealed a combined deletion/insertion in c-KIT exon 11 (V560delEins) in both the solid and the diffuse tumor component.
Case 2 was a 66-yr-old man who underwent segmental sigmoid colon resection for adenocarcinoma in a villous adenoma. Random sections
from grossly unremarkable colonic wall showed a diffuse proliferation of CD117+/CD34+ spindle cells completely replacing the muscularis
propria for a length of 6 mm. Molecular analysis revealed a somatic point mutation/ deletion in exon 11 of c-KIT (Q575L; L576_W582del).
Absence of multiple lesions and demonstration of a wild-type sequence for c-KIT in surrounding normal tissue ruled out the possibility of a
germline mutation in both cases. This peculiar diffuse form of sporadic ICC hyperplasia results from somatic c-KIT mutations and must be
distinguished from syndromic ICC hyperplasia associated with hereditary GIST syndromes. (IJCEP1005003).

Key words: GIST; Meckel Diverticulum; ICC hyperplasia; KIT mutation; hereditary GIST

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Address all correspondence to:
Abbas Agaimy, MD
Pathologisches Institut
Universitätsklinikum Erlangen
Krankenhausstraße 12
91054 Erlangen
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