Abstract
B-acute lymphoblastic leukemia (B-ALL) is commonly encountered in clinical practice.
Patients present with increased percentage of lymphoblasts in bone marrow and/or peripheral
blood. Immunophenotypic study by flow cytometry or immunohistochemistry is essential
to establish the diagnosis. Paired box-5 (PAX5) is a B cell lineage protein and terminal
deoxynucleotidyl transferase (TDT) is an immature marker, both of which are routinely
tested in the pathologic workup of acute leukemia. In this report, we describe a case
of B-ALL in a 37-year-old woman in which both PAX5 and TDT were negative. Next-generation
sequencing test detected mutations in DNA methyltransferase 3 α and Fms related receptor
tyrosine kinase 3 genes, which are frequently mutated in acute myeloid leukemia rather
than B-ALL. The constellation of these rare findings in a single case signifies the
importance of examining a wide panel of markers when the diagnosis of ALL is suspected.
Keywords
ALL - B-ALL - acute leukemia - TDT - PAX5 - immunohistochemistry - flow cytometry
- DNMT3A - FLT3
