The only category recognised as a distinct entity since the 2017 WHO classification is early T-cell precursor (ETP) T-ALL, which is defined by flow cytometry via the absence of CD8, CD1a, and CD5, and presence of specific myeloid or stem cell antigens in combination with typical T-ALL antigens (CD7 and cytoplasmic CD3)31. This evidence concerns the gene CD1A and acute lymphoblastic leukemia.