Laboratory diagnosis of acute myeloid leukemia with minimal differentiation switching to mixed phenotype acute leukemia: one case report

Abstract

Objective To analyze the diagnostic process of a rare case of acute myeloid leukemia with minimal differentiation undergoing a lineage switch to mixed phenotype acute leukemia, NOS-rare types,and to investigate its difference from other acute myeloid leukemia and mixed phenotype acute leukemia. Methods Following tests were performed on the patient with switched mixed phenotype acute leukemia and three control leukemia patients ( including two acute myeloid leukemia with minimal differentiation and one mixed phenotype acute leukemia ). Cell morphology was analyzed by bone marrow smear and related cell chemical staining. Immunophenotyping of bone marrow was performed by flow cytometry ( FCM ). G-banding technique was used for karyotype analysis and RT-PCR was used for fusion gene detection. All the laboratory data of the switched patient were compared to that of three control patients in order to reveal the characteristics of such a rare phenotype switch in acute leukemia. Results Before switching, the morphology of acute myeloid leukemia with minimal differentiation demonstrated 0.82 blasts occurring in bone marrow, distinct nucleoli and absence of Auer rods. Blast cells expressed hematopoieticassociated antigens ( CD38, HLA-DR ), myeloid antigens ( CD13, CD56, CD11b ) and CD7. And these blasts were negative for MPO, CD33, CD15, CD79, CD19, CD22, cytoplasmic CD3, CD4 and CD8. After switching, 0. 42 blasts were found in bone marrow, showed eosinophilia and presence of basophile. Blast cells expressed hematopoietic-associated antigens ( CD38, HLA-DR ), myeloid antigens ( MPO, CD13 ),lymphoid antigens ( CD19, CD79a ,cytoplasmic CD3, and CD7 ). The control group showed typical morphology and immunophenotyping. No abnormal karyotype and fusion gene were detected. Conclusions It is a rare and complicated case that acute myeloid leukemia with minimal differentiation switched to mixed phenotype acute leukemia, NOS-rare types. The laboratory features, especially the change of immunophenotyping play an important role in the diagnosis. Key words: Leukemia,myeloid,acute; Leukemia,biphenotypic,acute; Immunophenotyping; Flow cytometry