Autologous Testicular Tissue Transplantation

This study is testing whether frozen testicular tissue — collected from boys before cancer treatment that can cause infertility — can be transplanted back once they are adults to restore fertility. This is for men who had testicular tissue preserved in childhood and now wish to have biological children. **You may be eligible if...** - You are at least 18 years old - You had testicular tissue frozen (cryopreserved) before puberty as part of a fertility preservation program at the time of a cancer or blood disorder diagnosis - You now wish to become a parent - You are in a stable relationship with a female partner (cohabiting at least 1 year) - Your female partner is under 43 years old - You have had two semen analyses confirming no sperm (azoospermia) - Your cancer or blood disorder is in complete remission **You may NOT be eligible if...** - You have not reached complete remission - You are not in a relationship with a female partner - Your female partner is 43 or older - Your semen analyses show sperm is present Talk to your doctor to see if this trial is right for you.