For prepubertal patients, cryopreservation of testicular tissue is the only option available to preserve their fertility before cancer treatment. But testicular autograft raises the issue of the risk of reintroduction of potentially malignant cells. The aim of our study is to develop a specific and sensitive method for residual disease detection in the testicular tissue from patients treated for a solid tumor during infancy, whose fertility may have been compromised by treatments and who benefited of testicular tissue cryopreservation.