Risk of contralateral testicular cancer among men with unilaterally undescended testis: a meta analysis.

The association between undescended testis (cryptorchidism) and testicular cancer is established, but it is not known whether the risk of testicular cancer among men with unilateral maldescent is increased in both testes, or only on the undescended side. This is a meta-analysis of 11 case-control studies and 1 cohort study that all assessed the risk of testicular cancer separately for the undescended and descended testis. We used fixed-effects meta-analysis to calculate pooled estimates and 95% confidence intervals (CIs) for the relative risk. Of 199 tumors in men with unilateral cryptorchidism, 158 (79%) were on the ipsilateral side and 41 (21%) on the contralateral side. The pooled relative risks for testicular cancer in the ipsilateral and contralateral testis were 6.33 (95% CI, 4.30 to 9.31) and 1.74 (95% CI, 1.01 to 2.98), respectively. We conclude that in 1-sided undescended testis, the risk of testicular cancer may be increased in both testes, although to a much greater extent on the ipsilateral side.