title: The value of CD34, myeloperoxidase and chloroacetate esterase (Leder) stain in the diagnosis of granulocytic sarcoma.
abstract: BACKGROUND
  The differentiation of extramedullary myelogenous leukemia/granulocytic sarcoma (GS) from malignant lymphoma can sometimes be difficult. In the current study, we explored the value of CD34, myeloperoxidase and nonspecific esterase (Leder) stains in differentiating GS from lymphomas.
  
  
  METHODS
  Fifteen cases of phenotypically confirmed GS were stained for CD34, myeloperoxidase and Leder stains. The same stains were performed in 16 malignant lymphomas as controls. The GS cases were also immunostained for CD3 and CD20 to detect the incidence of aberrant T and B lymphocyte expression.
  
  
  RESULTS
  CD34 was expressed in 7 of the 15 cases of GS (46%). Myeloperoxidase was expressed in 10 of the 15 cases (66%), and Leder stain was positive in 9 cases (60%). All 15 cases had expression of at least one marker; 8 cases had expression of two markers and one case had expression of all 3 markers. None of the lymphomas showed expression of any of the three markers. Five cases (35%) of GS showed T cell antigen expression and 2 (14%) showed B cell antigen expression.
  
  
  CONCLUSIONS
  Our findings suggest that in cases of GS, the use of the combination of CD34, myeloperoxidase and Leder stains can help reach a definitive diagnosis, especially if lymphoma is difficult to exclude. Expression of B and T cell antigens in such lesions should not rule out the diagnosis of GS.
authors.affiliation: Department of Pathology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
authors.forename: W
authors.initials: W
authors.lastname: Mourad
authors.forename: H
authors.initials: H
authors.lastname: Kfoury
authors.forename: H
authors.initials: H
authors.lastname: Al Husseini