BCR-ABL1-like B-Lymphoblastic Leukemia/Lymphoma with FOXP1-ABL1 Rearrangement: Comprehensive Laboratory Identification Allowing Tyrosine Kinase Inhibitor Use.

B-lymphoblastic leukemia/lymphoma (B-ALL) is the most common type of childhood cancer; it also occurs in teenagers and adults, in whom the prognosis is generally less favorable. Therapeutic and molecular advances have substantially improved the treatment for subtypes of B-ALL, such that subclassification by cytogenetic and molecular alterations is critical for risk stratification and management. Novel rearrangements involving ABL1, JAK2, EPO, and other kinases have been identified that may respond to inhibition akin to BCR-ABL1. This diverse group of leukemias has been recognized as a provisional entity in the 2016 revision of the World Health Organization (WHO) Classification of the Hematopoietic Neoplasms as B-lymphoblastic leukemia/lymphoma, BCR-ABL1-like (Ph-like B-ALL). Herein, we present cytogenetic and molecular analysis of a case of B-ALL in a 16-year-old Caucasian boy with t(3;9) FOXP1-ABL1 rearrangement and concurrent loss of IKZF1, CDKN2A, and RB1 gene loci, meeting WHO criteria for Ph-like ALL. This case highlights diagnostic, prognostic, and therapeutic considerations of this recently recognized entity.