Lineage switch of acute myeloid leukemia to B-lymphoblastic leukemia in an adult at relapse with review of literature.

"Lineage switch" is a term used to describe the phenomenon of change of lineage of acute leukemia to a different lineage. It is typically seen during therapy or at the time of relapse. More commonly, it is described in the pediatric population with an incidence of 6-9%. Lineage switches, though uncommon, can occur from acute myeloid leukemia (AML) to acute lymphoblastic leukemia (ALL (B/T)) and vice versa. The present scenario of AML to B-ALL switch is rare in an adult, with only a handful of cases described in literature. We report herein a case diagnosed as AML at 56 years of age, with NPM mutation who relapsed after 18 months post initial diagnosis. The clinicopathological features, flowcytometry, and molecular characteristics are discussed.