Pediatric B-Lymphoblastic Leukemia with Aberrant CD117 Expression

Abstract

CD117 (c-Kit) is a tyrosine kinase receptor primarily expressed in myeloid lineage cells and certain acute myeloid leukemia (AML) subtypes. Its aberrant expression in acute lymphoblastic leukemia (ALL), particularly B-lymphoblastic leukemia (B-ALL), is rare. We present a pediatric case of B-ALL with unusual CD117 positivity and review of relevant literature to assess its prevalence, diagnostic challenge and clinical implications.

An 8-year-old girl presented with prolonged fever and melena, pancytopenia and 12% blasts on peripheral smear. Bone marrow immunophenotyping revealed 90% blasts expressing B-cell markers alongside myeloid markers CD117 and CD33, but negative for myeloperoxidase and monocytic markers, excluding mixed phenotype acute leukemia. Cytogenetics showed ETV6::RUNX1 fusion and hypertriploidy. The patient was treated with standard induction chemotherapy but developed fatal neutropenic colitis complicated by fungal infection.

CD117 expression in B-ALL is uncommon and may complicate diagnosis. Comprehensive immunophenotyping and molecular analysis are critical for accurate classification. While CD33 is frequently associated with ETV6::RUNX1-positive B-ALL, the prognostic role of CD117 remains unclear, warranting further study.