Types of testicular tumors
Germ cell tumors —This type affects cells within the testicles that make sperm. Germ cell tumors account for more than 90% of testicular cancers. These cancers are separated into two groups, seminomas and nonseminomas, which occur with about equal frequency. Some germ cell tumors contain both seminoma and nonseminoma tissue.
- Seminomas are less aggressive, which means they tend to grow slowly and usually do not spread (metastasize) to other parts of the body. There are two types of seminomas: classical (or typical), which make up about 95% of seminomas, and spermatocytic, which are rare and tend to occur in older men.
- Nonseminomas include four types: yolk sac tumors, teratomas, embryonal carcinomas, and choriocarcinomas. They often occur earlier in life and grow and spread more quickly than seminomas.
Stromal tumors — Fewer than 5% of testicular tumors in adults but as many as 20% of testicular tumors in children are stromal tumors. These tumors form in the tissues that support the testicles and make hormones. These types of tumors are usually noncancerous (benign). The two main types of stromal tumors are:
- Leydig cell tumors — These form in the cells that make male sex hormones, such as testosterone. The tumors themselves may make male sex hormones and sometimes they make the female sex hormone estrogen, which can lead to breast enlargement.
- Sertoli cell tumors — These affect the cells that support germ cells, which make sperm.
Sometimes other types of cancer, such as lymphoma, spread from other parts of the body to the testicles, but these are not true testicular cancers and they are treated differently than testicular cancer.