BTK and acute leukemia: As a result of karyotyping—FISH—PCR—NGS—validation comprehensive diagnostic work-up, three novel KMT2A rearrangements in childhood acute leukemia were discovered: ins(X;11)(q26;q13q25)/KMT2A-BTK, t(10;11)(q22;q23.3)/KMT2A-NUTM2A, and inv(11)(q12.2q23.3)/KMT2A-PRPF19.