Forty patients (9 females and 31 males; mean age 41.9 years) with CD7+ acute myelocytic leukemia (AML) were investigated; they were classified into the following subgroups according to French-American-British classification: 15 M1, 18 M2, 3 M4, and 4 M5. Leukemic cells from all the patients were negative for T-cell-specific antigens, surface CD3, and T-cell-receptor molecules. The sex and age distributions were different from those of CD7- AML patients (P < .01). Hepatomegaly and central nervous system involvement were also frequent in the CD7+ AML patients. The phenotype of and responsiveness to hematopoietic growth factors by the leukemic cells showed their immaturity, as evidenced by frequent expression of CD34, HLA-DR, and TdT, and the greatest growth response to interleukin-3. No particular karyotypic abnormality was shown. One hundred eighty AML patients were treated with a therapeutic regimen routinely used for AML. The CD7+ AML patients showed a significantly lower response than CD7- AML patients (P < .01), and had a poorer prognosis (P < .01). CD7+ AML patients with M1 or M5b had unfavorable responses to the therapeutic regimen in comparison with patients with M2, M4, or M5a. In addition, 3 of 4 CD7+ CD2+ AML patients, who did not respond to the therapy, were induced into complete remission with an acute lymphoblastic leukemia therapy. The results presented here indicate the diagnostic importance of CD7 positivity in AML, suggesting that the cellular and clinical characteristics of CD7+ AML are sufficient for it to be recognized as a distinct category of AML.

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