[Philadelphia chromosome positive acute mixed lineage leukemia with bcr (M-BCR-1) rearrangement]

We report two cases of Philadelphia (Ph1) chromosome positive acute mixed lineage leukemia (AMLL) with breakpoint cluster region (bcr) (M-BCR-1) rearrangement. A 31 year-old-man (case 1) and a 42 year-old-woman (case 2) were admitted to our hospital for further evaluation of leucocytosis with atypical blasts. Each case was diagnosed as having bilineal type of AMLL because: (1) blasts in each case consisted of larger myeloid cells positive for myeloperoxidase and small lymphoid cells positive for PAS, and blasts in case 2 were positive for TdT; (2) blasts in case 1 expressed B lymphoid associated antigen; (3) Southern analysis in each case showed clonal rearrangements of both the immunoglobulin heavy chain and the T cell receptor beta gene. These two cases demonstrated the Ph1 chromosome and rearrangement of the bcr (M-BCR-1) gene, but none of splenomegaly, basophilia, and additional chromosome abnormalities were observed. In addition, after achieving remissions, they didn't revert to chronic phase of chronic myelogenous leukemia (CML) and showed normal neutrophil alkaline phosphatase scores, and the Ph1 chromosome disappeared completely in case 1 and coexisted with the normal chromosome in case 2. These findings suggest that diagnosis of both cases should not be CML blast crisis (BC) but Ph1 positive acute leukemia, and Ph1 positive AMLL may be a distinct clinical entity to be distinguished from CML-BC.