Abstract:Objective To summarize the clinical features and cytogenetics of a case of BCR-ABL1p210-positive acute T lymphocytic leukemia(T-ALL) with pericentric inversion of chromosome 9[inv (9)]. Methods Chromosome karyotype analysis, flow cytometry detection of immunophenotype, and multiplex RT-PCR amplification of fusion gene were performed in an adult T-ALL patient admitted in March 2020. Results The patient complained of systemic poly skeletal pain for 1 month and abnormal hemogram for 1 day，and was diagnosed with T-ALL through a series of examinations after admission.Fusion gene detection showed: BCR-ABL1p210 positive [t(9;22)(q34;q11)]; Karyotype analysis showed: 46XY, t (5; 22) (p15.1; q12), inv (9) (p12q13) c. VP regimen chemotherapy was given，and the patient was discharged due to refusing to continue treatment after the first administration of vindesine, and died 3 days after discharge. Conclusion BCR-ABL1p210 positive with inv(9) can also occur in acute T-ALL. This case also includes the following features: elderly men, high leucocyte, elevated lactate dehydrogenase, multiple lymph node enlargement, hepatosplenomegaly, and cross-lineage expression of B-line and myeloid markers found in immunophenotypes.