RUNX1::RUNX1T1 Acute Myeloid Leukemia Cytogenetically Showing t(6;8)(p23;q22).

Runt-related transcription factor 1 (RUNX1)::RUNX1 partner transcriptional co-repressor 1 (RUNX1T1) acute myeloid leukemia (AML) is a subtype of acute leukemia primarily classified as French American British M2. RUNX1::RUNX1T1 transcript is formed by a reciprocal translocation between chromosomes 8q22 and 21q22. However, we encountered a case of AML that showed molecular positivity for RUNX1::RUNX1T1 fusion transcript but exhibited cytogenetically atypical translocation t(6;8). Fluorescence in situ hybridization (FISH) analysis, in combination with G-banding, clarified the three-way translocation t(6;21;8)(p25;q22;q22), which was partially cryptic. The case emphasizes the importance of employing molecular analysis alongside cytogenetics to determine disease subtypes in patients with acute leukemia.