Expression of Aberrant Antigens CD7 and CD19 in Adult Acute Myeloid Leukaemia by Flow Cytometry

Background : Flow cytometric immunophenotyping (FCI) is an indispensable tool for quantitative and qualitative evaluation of antigen expression of hematopoietic cells. From a diagnostic and therapeutic point of view, distinction between acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) and for diagnosis and definition of particular AML subtypes. Aberrant antigen expression (i.e. expression of an antigen which is inappropriate for a lineage) is rarely seen in normal bone marrow cells and their incidence is varied between various studies. Objectives : To explore the existence of the aberrant lymphoid antigens (CD7) and (CD19) in adult acute myeloid leukemia patients and their distribution among French-American-British (FAB) classification subtypes and correlate them with hematological parameters including red cell count (RBC) , hemoglobin, white cell count (WBC) , platelets count, blast cell percent and hematological response to the induction chemotherapy. Patients and Methods: EDTA anticoagulated peripheral blood (PB) sample of 2.5 ml and /or bone marrow (BM) aspirate samples of 0.5 ml from 25 cases of de novo AML including 14 male and 11 female with mean of age of 37.56±18.07 were included from June to November 2012.Hematological parameters including RBC, hemoglobin, WBC, platelets count, blast cell percent were obtained from the case file of the patients where they were done by automated device (Cell-DYN, RUBY list) and diagnosed by cytomorphology by Leishman stain and cytochemistry by Sudan Black B and PAS stain and AML cases were classified according to the FAB criteria. Aberrant lymphoid antigens, (CD7) and (CD19) expression was explored by CyFlow½ multiparametric flow cytometry at diagnosis. The patients were evaluated after three weeks of one cycle of chemotherapy for complete remission. Results: CD7, CD19 and co-expression of CD7 and CD 19 were expressed in 40%, 16% and 12% of AML patients respectively. Statistically significant associations were found between aberrant CD7 expressions and age, low WBC, and early FAB AML (M1, M2) subtypes. Complete remission was achieved in 19 out of 25 patients (76%) with standard chemotherapy whereas six patients did not achieved complete remission; three of them had aberrant CD7 expression (two of them died during induction therapy) and the other one had poor response to induction therapy.CD7 was detected in 7 patients; 6 of them were male. There is no statistically significant association between aberrant CD7 expression and hepatosplenomegaly and treatment response to one cycle of chemotherapy (P value > 0.05).Also there is no relation between CD7 expression and percent of blast cells. Conclusions: 1. The incidence of aberrant expression of CD7, CD19 and both CD7, and CD19 were 40%, 16%, and12% respectively. 2. CD7 was detected mainly in males whereas CD19 was distributed among males and females. 3. Total WBC count and malignant cell percent were lower in patients harboring aberrant expression compare to those without aberrant expression. 4. CD7 was mainly detected in early FAB classification (M1 and M2). 5. Six out of twenty five AML patients had no response to standard therapeutic regimen; three of them were harboring CD7 and no one had CD19 alone, thus we may propose that CD7 was associated with poor response to induction therapy.