Genotypic and immunophenotypic characterization of two human light chain-only B-cell non-Hodgkin's lymphomas

Two atypical human non-Hodgkin's lymphomas (NHLs) that exhibited unusual genotypic and in situ immunophenotypic abnormalities are described. Immunophenotypically, both NHLs lacked surface Ig heavy chains. With the exception of the MB2 B-cell-associated antigen, no B- and T-cell differentiation antigen was detected in case 1. NHL 2 failed to show evidence of clonality by immunohistochemical analysis but revealed the presence of many B-lymphocytes with an abnormal phenotypic profile: CD19+, CD20+, CD22+, kappa-, lambda-, CD9-, CD10-, CD21-, and CD24-. Genotypic analysis indicated that both lymphomas derived from anomalously matured pre-B-cells that had rearranged the lambda or kappa light chain genes but not the Ig heavy chain gene. The neoplastic cells of the two NHLs resemble the light chain-only B-cells recently discovered, following Epstein-Barr virus immortalization, in the human bone marrow. The authors' data confirm, therefore, the existence of the light chain-only B-cells in the human hematopoietic compartment. Moreover, their results emphasize the conclusive role of the immunogenotypic analysis in defining clonality, lineage, and maturation abnormalities of such atypical NHLs.