Large-cell "mixed-phenotype" lymphoma in AIDS. Identification of a CD5-expressing subset of B-cell non-Hodgkin's lymphoma.

We have characterized cells from an AIDS-associated non-Hodgkin's lymphoma (NHL). We found a malignant CD5+ B cell (approximately three-fourths of cells), with the balance of cells comprised of T cells having an activated phenotype. The lymphoma was unusual, in that all cells bear "T-lineage" markers, CD3 and CD5, and "B-lineage" markers, CD19 and CD20. Thus, conventional immunohistologic techniques were insufficient to type this mixture of cells; single-cell analysis was required. These "mixed-phenotype" lymphomas may occur frequently in AIDS-associated NHL. Our results show striking similarity to those obtained in the analysis of certain murine CD5+ B-cell lymphomas, suggesting that the study of lymphomagenesis in the mouse may aid in the understanding of AIDS-associated NHL.