Aberrant antigen expression detected by multiparameter three color flow cytometry in intermediate and high grade B-cell lymphomas

The aberrant expression of antigens (Ag) in lymphoproliferative disorders m ay cause a diagnostic problem when single parameter immunohistochemical ass ays are performed on frozen or paraffin sections because coexpression by re levant cells is not determined. This aberrant expression also raises the qu estion as to whether mixed lineage (biphenotypic) lymphoid proliferations e xist. Marrow (6) and extramedullary (20) tissues from 26 patients with diff use, intermediate and high grade, B-cell lymphomas (IWF E=1, F=1, G=19, H=1 and J=4) were analyzed with 19 markers using 3-color flow cytometry, The p ercentages (%) of patients with double Ag coexpression in at least 20% of t he CD19+ or CD20+ lymphoma cells were: stem cell(SC) Ag: CD10 = 58 and CD34 = 15; T-cell Ag: CD2 = 38, CD5 = 19 and CD7 = 19; myeloid(My) Ag: CD13 = 1 9 and CD33 = 8. The corresponding % with unusual triple Ag coexpression in at least 10% of the CD19+ B-cells were SC+T+ Ag: CD10CD2 = 50, CD10CD5=27, CD10CD7=38, CD34CD2=31, CD34CD5=19 and CD34CD7=27; T+T+ Ag: CD2CD5 = 35, CD 2CD7 = 42 and CD5CD7 = 31; T+My+ Ag: CD2CD13 = 35 and CD2CD33 = 12; and MyMy+ Ag: CD13CD33 = 12. Ten of 12 lymphomas tested showed clonal immunoglobu lin (Ig) heavy chain gene rearrangements in the absence of clonal T-cell re ceptor (TCR) gene rearrangements. None(0%) of the My Ag positive cases show ed immunoreactivity for myeloperoxidase. We conclude that the anomalous T a nd My Ag expression seen in the above B-cell lymphomas is not indicative of mixed lineage proliferation but represents the aberrant expression of thes e antigens by the malignant cells.