Clinical and biological characteristics of adult biphenotypic acute leukemia in comparison with that of acute myeloid leukemia and acute lymphoblastic leukemia: a case series of a Chinese population.

BACKGROUND Biphenotypic acute leukemia is a rare disorder that is difficult to diagnose. It displays features of both myeloid and lymphoid lineage. There is still a lack of studies in biphenotypic acute leukemia in a Chinese population. We present here a comprehensive investigation of the clinical and biological characteristics, and outcome of biphenotypic acute leukemia in our hospital in over a seven year period. DESIGN AND METHODS We retrospectively analyzed 452 adult acute leukemia patients diagnosed according to French-American-British (FAB) classification and biphenotypic acute leukemia diagnosed according to European Group for the Immunological Characterization of Leukemias (EGIL) classification, respectively. Biological characteristics, response to treatment, and outcome were examined in biphenotypic acute leukemia patients and compared with that in acute myeloid leukemia and acute lymphoblastic leukemia patients with complete follow-up profiles diagnosed in the same period. RESULTS Of 452 acute leukemia patients, 21 cases (4.6%) were diagnosed as biphenotypic acute leukemia. Among them, 14 (66.7%) were B lymphoid and myeloid, 5 (23.8%) were T lymphoid and myeloid, one (4.8%) was T/B lymphoid and one (4.8%) was trilineage differentiation. When compared with acute myeloid leukemia and acute lymphoblastic leukemia, patients with biphenotypic acute leukemia showed significantly higher incidence of CD34 antigen expression, unfavorable karyotypes, and extramedullary infiltration (p<0.05). In this cohort of patients with biphenotypic acute leukemia, t(9;22) was the most common abnormality in chromosome structure. The median disease-free survival and overall survival in biphenotypic acute leukemia patients was five months and ten months, respectively, significantly shorter than those in acute myeloid leukemia and acute lymphoblastic leukemia patients (p<0.05). CONCLUSIONS The prognosis of biphenotypic acute leukemia patients is poor when compared with de novo acute myeloid leukemia or acute lymphoblastic leukemia. Biphenotypic acute leukemia patients showed a much higher incidence of CD34 antigen expression, complex abnormal karyotype, extramedullary infiltration, relapse, and resistance to therapy after relapse.