Tumor in testicle for my 8 month old.

My baby is 8 month old now. He has a painless swelling or tumor in his left testis. His afp level is 5000. What is the cause and is this because of using disposable diapers.. We have gone to Ramachandra hospital and removed one of his testis yesterday. They said it is a tumor coz his alpha fetoprotein level is 5000 in blood test results.. They sent the removed testis for pathological analysis. I'm worried about the cause. I really don't know why he got this tumor. Some people saying that it's because of using disposable diapers and the chemicals in it. Or may be because of heat caused by wearing those diapers.. Is it true? After surgery doctor itself adviced to put on diapers.. I'm confused doctor. Please tell me what could be the cause of this tumor?