Abstract
To detect hybrid acute leukemia (HAL), we analyzed the surface markers of leukemic cells in 51 patients with acute leukemia and blastic crisis of chronic myelogenous leukemia (CMLBC). By means of dual staining of surface antigens of leukemic blasts using FACScan, we found there were more HAL cases than expected.
HAL was defined as the state in which leukemic cells had at least co-existence of one myeloid marker and two lymphoid markers. Myeloid markers consisted of CD 13, CD 33 and peroxidase and lymphoid markers consisted of CD10 (CALLA), CD 19, CD 20 and terminal deoxynucleotidyl transferase activity (TdT).
According to this definition, 7 of 20 acute lymphoblastic leukemia (ALL) cases, 2 of 9 CMLBC cases, and 1 of 22 acute non-lymphocytic leukemia (ANLL) cases corresponded to HAL.
Except for one case of ANLL, all HAL cases consisted of biphenotypic leukemia. In most of the biphenotypic leukemia cases, leukemic cells commonly presented CD 10 (CALLA) and CD 19 as lymphoid antigens, and CD 33 as myeloid antigen. In addition to this, leukemic cells in two ALL cases were positive for CD 13 antigen which was considered to be more specific for myeloid lineage. However these cells were positive for CD 10, CD 19 and TdT, and negative for peroxidase, so ALL was diagnosed both phenotypically and with cytochemistry. Pathological cells in one case of CMLBC were positive for CD 10, TdT, CD 13 and CD 33. In one case of ANLL, leukemic cells were peroxidase-positive and M2 of the FAB classification was diagnosed, but those cells were mixed with a small number of peroxidase-negative leukemic cells. The latter cells were positive for CD10 and TdT. Therefore this case was regarded as bilineal leukemia.
These results clearly indicated that HAL occurred at a higher rate than we had expected in acute leukemia and CMLBC.
