Various subsets of DLBCL are distinguished based on molecular and immunohistochemical features. CD5 expressing DLBCL (CD5+ DLBCL) is increasingly recognized as a subtype of DLBCL with an aggressive disease course. Primary CD5+ DLBCL comprises approximately 5-10% of DLBCL. Few studies of CD5+ DLBCL have been reported, primarily from Japan. Publications covered in this review include articles published on PubMed and abstracts from major international conferences until April 2013. Common features of patients with CD5+ DLBCL are older age, female preponderance, elevated LDH, more extra-nodal involvement, poor performance status (PS), higher incidence of CNS involvement, inferior response to rituximab-containing regimens (as compared to CD5- DLBCL) and advanced stage. The majority of these cases belong to the activated B cell subtype (ABC) of DLBCL. It is unclear whether CD5 expression in malignant B cells may confer chemo resistance, upregulate antiapoptotic signals and alter the microenvironment. Molecular techniques have helped in understanding CD5+ DLBCL. Gene expression signature was similar in ABC-DLBCL and CD5+ DLBCL in some studies. Despite the better characterization treatment outcomes are poor and additional studies are needed.
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