B-lymphoid blast crisis and subsequent lymphoid-myeloid crisis were observed in a 64-year-old woman with Ph1 positive chronic myelocytic leukemia (CML).
In the first crisis, blast cells showed B-lymphoid characteristics with surface markers such as B4 (83.8%), Ia (87.0%), J5 (72.8%), and My7 (5.0%). She responded well to the VP therapy. In the second crisis, however, blast cells showed both lymphoid and myeloid characteristics with surface markers such as J5 (63.5%), My7 (82.3%), My4 (9.7%), and My9 (12.4%). By the two color analysis with PE-My7 and FITC-J5, 45.3% of the blast cells had both lymphoid and myeloid surface markers. Throughout the first and second blast crises, immunoglobulin gene rearrangement was observed.
This case suggests that CML is a clonal disorder which can transform into both lymphoid and myeloid cells, and that in the lymphoid crisis the precursor cell is capable of immunoglobulin gene rearrangement and represents discrete step in early B-cell maturation.
