Abnormal B-lymphoblasts in myelodysplastic syndromes and myeloproliferative neoplasms other than chronic myeloid leukemia.

These findings demonstrate that phenotypically detectable abnormal immature B lineage output occurs in MDS and non-CML MPN, albeit rarely. While presence of ABLB does not necessarily reflect blast crisis, the underlying disease biology of our findings may ultimately be relevant to patient management and warrants further investigation.