AFF1 and acute lymphoblastic leukemia: While the overall outcome of acute lymphoblastic leukemia (ALL) has improved markedly over the past decades, the prognosis for adults (>40 years), relapsed cases, or high-risk genetic subtypes such as the KMT2A::AFF1-rearrangement (t(4;11)(q21;q23), KMT2A-r, formerly known as MLL::AF4), remains poor [1].