The M3 subtype of acute myelogenous leukemia (AML) is Acute promyelocytic leukemia (APL). It is the cancer of white blood cells. The retinoic acid receptor-alpha (RARA) gene on chromosome 17 is involved in a reciprocal translocation with the promyelocytic leukemia gene (PML) on chromosome 15, a translocation denoted as t(15;17) to give rise to AML-M3. The fusion protein interacts with the sites on the cell’s DNA which blocks transcription and differentiation of granulocytes. Thus, the PML/RARA t(15;17) test is useful for diagnosis and predicting treatment response.