BCR GENE REARRANGEMENT ANALYSIS IN MYELOPROLIFERATIVE DISORDERS OTHERTHAN CHRONIC MYELOGENOUS LEUKEMIA

The bcr gene rearrangement resulting from the Philadelphia translocati on is diagnostic of chronic myelogenous leukemia (CML) and is consider ed the hallmark of this myeloproliferative disorder (MPD) at the molec ular level. The other MPDs, essential thrombocythemia (ET), polycythem ia vera (PV), agnogenic myeloid metaplasia (AMM), and unclassified MPD , share morphologic features with CML, making the diagnosis difficult in cases with considerable morphologic overlap. In such cases, molecul ar analysis becomes essential for accurate diagnosis. We report result s of bcr analysis by Southern hybridization in 37 patients with MPDs o ther than CML: ET (20 cases), PV (seven cases), unclassified MPD (nine cases), as well as in one case of chronic myelomonocytic leukemia (CM ML). bcr negativity ruled out CML in 36 cases, confirming the morpholo gic diagnosis. In one case diagnosed as ET, bcr gene rearrangement was diagnostic of CML. The correct diagnosis made possible a different th erapeutic approach in this young patient and resulted in cure after al logeneic bone marrow transplantation. The existence of such cases make s the use of molecular analysis essential in the evaluation of MPDs, e ven when the morphologic features do not unequivocally support the dia gnosis of CML, as in this patient.