Expression of the c-kit receptor (CD117) is a feature of almost all subtypes of de novo acute myeloblastic leukemia (AML), including cytogenetically good-risk AML, and lacks prognostic significance

Because of conflicting reports on the prognosis of patients with c-kit rece ptor positive AML and lacking correlations with cytogenetic analyses, we pr ospectively evaluated the c-kit receptor expression in 917 AML patients (75 0 adult patients; 167 children) using flow cytometry and compared the resul ts to the immunophenotype, morphological and cytogenetic findings as well a s clinical outcome. Expression of the c-kit receptor was present in 63% of all AML investigated. Among these an immature immunophenotype was more freq uent and 30% had a CD34+/CD15- and 37% a CD34+/CD14- phenotype, whereas onl y 9% and 10% showed these phenotypes in the c-kit receptor negative group, respectively. C-kit receptor expression ranged average in MO and M1 subtype s (69% versus 70%) but was less pronounced among M5 subtypes (21%). Results of karyotyping were available in 280 patients. C-kit receptor expression o ccurred in 37 of 42 (88%) patients with favorable cytogenetic abnormalities such as t(8;21), t(15;17) or inv(lb) which exceeded the expression rate in patients with intermediate risk, poor risk or other abnormalities. Informa tion about the clinical outcome was available in 228 patients treated accor ding to the protocols of two German multicenter trials (AML-BFM, AMLCG). We found no difference of CR-rate or event-free survival (EFS) in adults with or without c-kit receptor expression, Children with c-kit receptor negativ e AML had a lower CR-rate and EFS, but also a lower median age and a higher frequency of M5 subtype as compared to children with c-kit receptor expres sion. In conclusion, analysis of c-kit receptor expression may help to identify p henotypically immature AML but fails to identify myeloid differentiation of leukemic blasts in approximately one third of patients. We found no eviden ce of an adverse prognosis in AML patients with c-kit receptor expression. Analysis for c-kit receptor expression does not appear to add information t o established prognostic parameters in AML.