It is characterized by an excess of abnormal hypergranular promyelocytes in the bone marrow and other hematopoietic organs, and chromosomal translocation t(15;17)(q22;q21) leading to fusion of the genes encoding promyelocytic leukemia protein(PML) and retinoic acid receptor alpha (RARα) to generate the PML-RARα oncoprotein [2 ].
Source: wiktionary