Seminoma is a cancer of the testicles which arise from the cells that line the tubules that carry semen. They are generally found as a lump or mass on one of the testicles. They usually develop on young men aged 15-35. Although they are malignant, they are generally easy to treat and have a good prognosis.
A common treatment is removal of the affected testicle. As a rule, this does not affect fertility or testosterone production as the remaining testicle increases production of testosterone. However, radiation therapy and chemotherapy are also commonly used and are usually successful.