RESUMO
The occurrence of mediastinal germ cell tumor and breast cancer have been repeatedly reported in men with Klinefelter syndrome (KS) but this association is debated controversially for patients with hematologic malignancies. The authors describe 2 tall adolescents in whom diagnostic workup for acute lymphoblastic leukemia (ALL) revealed 47,XXY and 47,XXY/48,XXXYkaryotype, respectively. Among 4195 registered male patients in the ALL-BFM study group since 1983, no further patients with ALL and KS were identified. Given the lack of epidemiological data, this retrospective analysis illustrates the association of previously described cases of hematologic malignancies with KS. In contrast to other chromosomal aberrations, the incidence of ALL does not seem to be increased in pediatric patients with KS.