Lineage Switching from Acute Myeloid Leukemia associated with Systemic Mastocytosis to B-Acute Lymphoblastic Leukemia: A Diagnostic Dilemma

Abstract

Relapse acute leukemia is defined as the reappearance of more than 5% blast in the bone marrow. In most instances, blast expresses the specific lineage (myeloid or lymphoid), similar to a diagnosis. However, it rarely converts to a different lineage, either myeloid shifting to lymphoid or vice versa, during relapse. Thus, it is labelled as switching lineage acute leukemia, after excluding the criteria for mixed phenotypic acute leukemia, which can be a challenge to diagnose. We describe a 24-year-old gentleman with a known case of acute myeloid leukemia associated with systemic mastocytosis (SM); eight months later and after two complete cycles of chemotherapy, relapse occurred with a switched lineage to B-acute lymphoblastic leukemia. The laboratory investigation approaches and the challenges in the diagnosis are also discussed in this case report