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

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