title: Distribution of neural cell adhesion molecule (NCAM/CD56) in gastrointestinal stromal tumours and their intra-abdominal mesenchymal mimics.
abstract: BACKGROUND
  The distribution and reactivity pattern of neural cell adhesion molecule (NCAM/CD56) in gastrointestinal stromal tumours (GISTs) and their mesenchymal mimics have not been investigated in the KIT era.
  
  
  METHODS
  275 histologically and immunohistochemically well characterised primary and metastatic intra-abdominal mesenchymal lesions were analysed by conventional immunohistochemistry, with emphasis on GIST and GI smooth muscle neoplasms.
  
  
  RESULTS
  CD56 expression was seen in 18/21 (86%), 4/5 (80%), 26/34 (76%), and 32/168 (19%) of primary GI leiomyomas, schwannomas, leiomyosarcomas, and GISTs, respectively. Reactivity in GISTs was mostly focal. Of 6% strongly staining GISTs, 71% were either malignant clinically or assigned a high risk prognostic group. CD56 expression in GISTs varied greatly with histological type (seen in 50% and 7% of epithelioid and spindled GISTs, respectively) and anatomical site (in 33%, 10%, 1%, and 0% of rectal, gastric, small intestinal and oesophageal GISTs, respectively). A variable, but inconsistent expression was seen in miscellaneous lesions including dedifferentiated liposarcoma, abdominopelvic PEComa, myo/fibroblastic sarcoma and malignant fibrous histiocytoma. Mesenteric fibromatoses, angiosarcoma/Kaposi sarcoma, reactive tumefactive fibrogenic lesions and 12/13 primary anorectal and oesophageal melanomas were negative.
  
  
  CONCLUSIONS
  Results confirmed the ubiquity and non-specificity of CD56 as a neurogenic marker. Except for a subset of epithelioid gastric and high-grade rectal GISTs, CD56 expression is rare in GISTs, contrasting with true leiomyomatous and neurogenic neoplasms. CD56 plays a limited role in the differential diagnosis of GIST. Its potential role as a marker of adverse outcome in GISTs remains to be further investigated.
authors.affiliation: Institute of Pathology, Klinikum Nürnberg, Nürnberg, Germany. abbas.agaimy@klinikumnuernberg.de
authors.forename: A
authors.initials: A
authors.lastname: Agaimy
authors.forename: P H
authors.initials: PH
authors.lastname: Wünsch
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D019002:CD56 Antigen / Q000378:metabolism*; D003937:Diagnosis, Differential; D005354:Fibrosarcoma / Q000175:diagnosis / Q000378:metabolism; D046152:Gastrointestinal Stromal Tumors / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D008545:Melanoma / Q000175:diagnosis / Q000378:metabolism / Q000556:secondary; D009363:Neoplasm Proteins / Q000378:metabolism*; D009379:Neoplasms, Muscle Tissue / Q000175:diagnosis / Q000378:metabolism; D018317:Nerve Sheath Neoplasms / Q000378:metabolism; D011379:Prognosis
chemical_list: D014408:Biomarkers, Tumor; D019002:CD56 Antigen; D009363:Neoplasm Proteins