Electron Microscopic identification of Pre-B Lymphocytes in the Bone Marrow of a Patient with Chronic Myelocytic Leukemic in Blast Crisis
There have been numerous reports in the current literature suggesting that hematopoietic precursor cells in some human chronic myelocytic leukemias (CML) undergo lymphoblastic transformation at the time of the acute blast crisis (BC) stage. The primary evidence offered in support of this transformation theory--lymphoblastic appearing morphology, increased terminal deoxynucleotidyl transferase (TdT) activity, and chemotherapeutic sensitivity to vincristine and prednisone--has been indirect, however, since these features may occur in nonlymphoid cells. More direct support for the Pre-B lineage of these cells has recently been provided by immunofluorescent light microscopic studies demonstrating the presence of intracytoplasmic immunoglobulin M (IgM) in these CML-BC cells.