Biphenotypic acute leukaemia (BAL) is an uncommon type of leukemia which arises in multipotent progenitor cells which have the ability to differentiate into both myeloid and lymphoid lineages. It is a subtype of "leukemia of ambiguous lineage". The direct reasons leading to BAL are still not clear. BAL can be de novo or secondary to previous cytotoxic therapy. Many factors, such viruses, hereditary factors, and radiation, might have a relationship with BAL. BAL is hard to treat. Usually the chemotherapy is chosen according to the morphology of the blast (ALL or AML). A blood-forming stem-cell transplantation is highly recommended. About 5% of acute leukaemia cases are BAL. BAL can occur in all ages of people but occurs more in adults than in children. Signs and symptoms BAL has similar symptoms to other types of leukemia, but they are usually more serious. Symptoms caused by bone marrow damage Bruising, spotting: the reason is lack of platelets. it is very common in BAL patients, most of patients die due to the A low level of red blood cells in the bloodstream: Because the decline of hematopoietic function, need blood transfusion therapy Persistent fever, infection prolonged healing: Diffuse hemorrhage: which is dangerous and might lead to death. Symptoms caused by blood cancer cells infiltration into tissues: Swollen lymph nodes Joint pain Swelling of the gums Enlargement of the liver and spleen Headache and vomiting: blood cancer infiltration into the wear performance of the central nervous system. Skin lumps: Because look was slightly green, also known as the "Green tumor." Pericardial or pleural effusion Causes The cause that directly leads to BAL is unclear. Exposure to radiation, chemical exposure, virus and genetics are the primary reasons proposed by researchers. Mechanisms The mechanism of BAL is related to several mutations. The most common abnormalities are t(9;22) and MLL gene rearrangement at 11q23. T(9;22) affect the ABL gene at 9q34 and BCR at 22q11. The hybrid gene product ABL/BCR is an oncogene which could lead several types of leukemia including BAL. ABL/BCR could active several molecular pathways: RAS signaling could be activated by BCR/ABL by GRB2 adaptor which interact with Y177 of BCR. Through AKT/PKB, PI3-K pathway could also be activated. STAT5, 1, and 6 has been reported that is a major molecular signaling event activated by BCR/ABL. Some focal adhesion complex (PAXILLIN, FAK0 could be activated by BCR/ABL with adaptor molecule CRK-L. BCR/ABL could inactivate