Klinefelter syndrome (KS) is a sex chromosome abnormality occurring in 1 in 1,000 males. An association with leukemia, germ cell tumor, and male breast cancer has been suggested in KS. Such information is important for professionals caring for KS patients as the condition is frequently not clinically recognizable until after puberty. We report on a renal cell carcinoma (RCC) in a 10-year-old boy with KS. He developed intermittent hematuria at age 10 years and was diagnosed with a right kidney mass, which on pathology was identified as RCC. In addition, he was known to have learning disabilities and language delays. Analysis of peripheral blood chromosomes showed a 47,XXY karyotype while analysis of tumor cells demonstrated clonal abnormalities including a translocation between chromosomes X and 1, designated 47,XXYc,t(X;1)(p11.2;q21)[6]/47,XXYc,t(X;1),r(Xp)[2]/46,X XYc,-X,t(X;1)[7]. Renal cell carcinoma is rare in childhood and is not previously reported in KS. The oncogenetic significance of the chromosomal regions involved in this translocation is discussed in relation to the congenital abnormality of the patient.

Klinefelter syndrome (KS) is a sex chromosome abnormality occurring in 1 in 1,000 males. An association with leukemia, germ cell tumor, and male breast cancer has been suggested in KS. Such information is important for professionals caring for KS patients as the condition is frequently not clinically recognizable until after puberty. We report on a renal cell carcinoma (RCC) in a 10-year-old boy with KS. He developed intermittent hematuria at age 10 years and was diagnosed with a right kidney mass, which on pathology was identified as RCC. In addition, he was known to have learning disabilities and language delays. Analysis of peripheral blood chromosomes showed a 47,XXY karyotype while analysis of tumor cells demonstrated clonal abnormalities including a translocation between chromosomes X and 1, designated 47,XXYc,t(X;1)(p11.2;q21)[6]/47,XXYc,t(X;1),r(Xp)[2]/46,X XYc,-X,t(X;1)[7]. Renal cell carcinoma is rare in childhood and is not previously reported in KS. The oncogenetic significance of the chromosomal regions involved in this translocation is discussed in relation to the congenital abnormality of the patient.