DETECTION OF CD5 ANTIGEN ON B-CELL LYMPHOMAS IN FIXED, PARAFFIN-EMBEDDED TISSUES USING SIGNAL AMPLIFICATION BY CATALYZED REPORTER DEPOSITION

CD5 surface antigen is expressed on some categories of B cell lymphoma s. The detection of CD5 coexpression on malignant B cell infiltrates, particularly in small biopsy specimens, is useful in distinguishing be tween small lymphocytic lymphoma, mantle cell lymphoma, low grade marg inal zone B cell lymphoma, and follicular small cleaved cell lymphoma. However, conflicting results have been reported with regard to the de tection of CD5 antigen expression on B cell non-Hodgkin's lymphomas (B -NHLs) in fixed, paraffin embedded tissues using routine immunohistoch emical (IHC) staining techniques. We used catalyzed reporter depositio n (CARD) as a strategy to amplify the IHC signal and consequently incr ease the sensitivity of antigen detection. CARD improved detection of CD5 antigen without sacrificing specificity of the test. In our study, virtually all malignant B-NHLs with CD5 antigen expression showed str ong immunoreactivity for a commercially available anti-CDS monoclonal antibody using CARD, whereas the majority of the same lymphomas did no t label for CD5 using routine IHC without CARD amplification. The conc ordance between CD5 antigen detection by immunophenotyping of fresh or frozen tissues and immunostaining with CARD amplification on paraffin fixed tissue sections was 100%. It appears that this method can be ap plied in the diagnostic evaluation of B-NHLs or in other situations th at a weak antigen signal is present.