Immunophenotypic analysis of primary malignant lymphoma of the brain

The immunophenotypes in three cases of primary malignant lymphomas of the brain were analyzed by flow cytometry using a panel of monoclonal antibodies. In all three cases the immunophenotypes were CD10 negative, CD19 positive, and CD20 positive, and in two cases human leukocyte antigen (HLA)-DR positive. CD20 showed high positivity (80-97%), while CD19 revealed low positivity (30-50%). These neoplastic cells apparently became malignant at the B-cell differentiation stage, when they expressed both CD19 and CD20. Differentiation continued until CD19 was no longer expressed, when further differentiation stopped between the last stage of B-cell differentiation and the early stage of plasma cell formation (Case 3 was CD38 positive). Case 1 was immunoblastic type lymphoma and the cells were both surface immunoglobulin and HLA-DR negative. At least 40% of Case 2 cells showed both B-cell and T-cell markers. Immunophenotypic study can help determine the cell lineage, clonality, and stage of differentiation of lymphoid neoplasms.