A shadow in the treatment of acute leukemia: lineage switch.

Lineage switch is a rare phenomenon in which acute myeloid leukemia (AML) transforms into acute lymphoblastic leukemia (ALL) and vice versa, sharing the same clonal origin. It is more common for AML to relapse as ALL. Cytogenetics, microenvironment, and preceding therapies are associated with lineage switch. Since the etiology of lineage switch is unclear, presumptions include clonal selection, pluripotent stem cells, and differentiated cell trans-differentiation or re-differentiation. The key point for diagnosing lineage switch is that the relapsed tumor originates from the common cell of the primary leukemia, although it is occasionally derived via clonal evolution. It is very important to distinguish lineage switch from other illnesses, such as secondary leukemia or the blast phase of chronic leukemia. Although direct treatment of the present lineage results in an improved prognosis, the outcome of these patients remains poor, with low survival and rapid progression. Hematopoietic stem cell transplantation can extend survival. Lineage switch risk-adapted management stratification may be beneficial for detecting relapse and more promptly provide suitable therapy. Efficient and toxicity-restricted therapy is being developed to improve the very poor prognosis.