title: Immunohistochemical comparison of gastrointestinal stromal tumor and solitary fibrous tumor.
abstract: BACKGROUND
  The differential diagnosis of gastrointestinal stromal tumors (GIST) and solitary fibrous tumors (SFT) may be a diagnostic challenging because of overlapping clinicopathologic features. Many studies have shown consistent immunoreactivity for CD117 (c-Kit) in GIST. However, only a few studies have evaluated CD117 expression in SFT, and these studies have used an antibody from Santa Cruz Biotechnology. In non-GIST lesions, reactivity with this antibody has been shown to differ from that with a CD117 antibody from Dako Corporation. The immunoreactivity of SFT with the Dako CD117 antibody has not been reported. Conversely, CD99 is a marker for SFT, and its expression in GIST has not been evaluated.
  
  
  OBJECTIVE
  To study the immunohistochemical profiles of GIST and SFT to evaluate their diagnostic overlap.
  
  
  METHODS
  We studied the immunoreactivity of 27 unequivocal GIST and 19 unequivocal extra-abdominal SFT for CD117, CD34, CD99, alpha-smooth muscle actin, vimentin, CD31, S100 protein, and muscle-specific actin. All antibodies, including CD117, were from Dako Corporation.
  
  
  RESULTS
  We found positive immunoreactivity for CD117 in 100% of GIST and none of SFT; for CD34 in 89% of GIST, and 100% of SFT; for CD99 in 89% of GIST and 100% of SFT; for alpha-smooth muscle actin in 48% of GIST and 31% of SFT; for vimentin in 89% of GIST and 90% of SFT; and for muscle-specific actin in 22% of GIST and none of SFT. None of the GIST or SFT showed immunoreactivity for CD31 and S100 protein.
  
  
  CONCLUSIONS
  The major difference between GIST and SFT was strong CD117 immunoexpression in all GIST and an absence of this expression in all SFT. With the exception of muscle-specific actin, the prevalence of immunoreactivity for the markers studied did not differ substantially between these 2 tumors. We conclude that GIST and SFT show distinctly divergent immunoprofiles with respect to CD117 and muscle-specific actin.
authors.affiliation: Department of Pathology, Medical College of Wisconsin, Milwaukee 53226, USA. vshidham@mcw.edu
authors.forename: Vinod B
authors.initials: VB
authors.lastname: Shidham
authors.forename: Mamatha
authors.initials: M
authors.lastname: Chivukula
authors.forename: Dilip
authors.initials: D
authors.lastname: Gupta
authors.forename: R Nagarjun
authors.initials: RN
authors.lastname: Rao
authors.forename: Richard
authors.initials: R
authors.lastname: Komorowski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D005350:Fibroma / Q000378:metabolism* / Q000473:pathology; D005770:Gastrointestinal Neoplasms / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000378:metabolism; D017154:Stromal Cells / Q000378:metabolism* / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins