CD 34 immunotyping of blasts in myelodysplasia

We studied the expression of the hematopoietic progenitor cell antigen CD 34 in six patients with refractory anemia with excess of blasts (RAEB), five patients with RAEB in transformation (RAEB-T), and seven patients with chronic myelomonocytic leukemia (CMML). Immunocytochemical labeling of bone marrow cells was performed by an indirect immunoperoxidase method with preservation of morphological details. The cells were stained with May-Grunwald-Giemsa, photographed, destained, and immunolabeled by the immunoperoxidase technique. We found 1.5±0.5% blasts and 0.8±0.4% CD 34+ blasts in normal bone marrow. The CD 34 positivity of blasts was 53±9%. The patients with RAEB showed 1.7±1.4% CD 34+ blasts. The CD 34 positivity of blasts (11.8±5.6%) was lower than in normal bone marrow. The patients with RAEB-T had a higher percentage of CD 34+ blasts (7.3∓3.4) and a higher CD 34 positivity of blasts (28.2±14.6%) than patients with RAEB. The CMML patients showed a percentage of CD 34+ blasts and a CD 34 positivity of blasts in the range of RAEB. We found an increase of promonocytes (PMC) in 5/7 patients. In some patients the PMC were CD 34 positive. Our results indicate that the increase of blasts in REAB is related to CD 34-negative blasts. With progression to RAEB-T the percentage of CD 34-positive blasts increased. Some of the CMML patients also showed a population of CD 34-positive PMC. A clone of undifferentiated CD 34-positive cells is characteristic for patients with these types of myelodysplasia.