A PRIMITIVE VARIANT OF BLAST CRISIS IN CH RONIC MYELOID-LEUKEMIA (CML)

While immunotyping blast cells from 45 patients with CML blast crisis, we detected 5 cases with immunologically primitive blast cells. The i mmunological phenotype of these cells corresponded to that of primitiv e stem cells which are characterized by expression of CD34 and HLA-DR antigens in tile absence of other immunological markets. We suggest th at blast cells from these patients may undergo differentiation similar to that of primitive stem cells that implies the existence of a new i mmunological variant of CML blast crisis, a primitive variant. Morphol ogically, blast cells in 3 cases could be classified as myeloid, in 2 cases precise identification was impossible. Cytochemically, this type of cells can be defined as mixed. The patients with CD34(+) phenotype do not differ clinically or hematologically from those with CML blast crisis. Blast cells with membrane marker CD34 are likely to arise in any CML phase either as a component of overall leukemic population of predominant, single subclone.