Detection of immunophenotypic abnormalities in paraffin-embedded B-lineage non-Hodgkin's lymphomas

The authors analyzed the frequency of immunophenotypic abnormalities in 1,474 cases of routinely fixed, paraffin-embedded B-lineage non-Hodgkin's lymphomas. B-lineage was determined by immunoreactivity for CD20 (L26, 92%); CD45RA (4KB5, an additional 3%) or immunoglobulin (Ig) light chain restriction (remaining 5%). CD45RA was found to be especially helpful on Bouin's-fixed or decalcified tissue and Ig staining was most helpful in plasmacytoid lesions. Coexpression of the T-cell marker CD43 (Leu-22) was the most common immunophenotypic abnormality, seen in 60% of mantle cell lymphomas (MCL), 39% of CLL/small lymphocytic lymphomas, 16% of diffuse large cell lymphomas (DLCL), but only 5% of follicular lymphomas (FL). Antibodies to CD45RO (A6 and UCHL1) and CD3 (polyclonal) were useful in distinguishing infiltrating T cells from B cells coexpressing CD43. Ig light chain restriction was the next commonest immunophenotypic abnormality, which was identified in 67% of plasmacytoid diffuse small cell lymphomas, 43% of MCLs, 35% of monocytoid B-cell lymphomas and 28% of FLs. Overexpression of bcl-2 oncogenic protein was observed in 71% of FLs (n = 96), but not in a control group of reactive follicular hyperplasias (n = 34). Combining two criteria increased the sensitivity of immunodiagnosis in certain circumstances.