It should be noted, however, that it is important to discriminate between CLL-like MBL, which has CD5 and CD23 expression along with weak CD20, CD79b and surface immunoglobulin, and other sub-types of MBL. The two most common non-CLL types are CD5− MBL (classified as “non-CLL phenotype MBL”) and CD5+ MBL with a phenotype that is not typical for CLL, i.e. strong CD20, CD79b or immunoglobulin expression (classified as “atypical-CLL phenotype MBL”). Individuals with a CD5+, CD23 negative phenotype must have the diagnosis of mantle cell lymphoma excluded by FISH evaluation for the t(11;14) before being classified as having atypical-CLL phenotype MBL.
