About 95 percent of testicular cancers begin in germ cells, specialised cells in the testicles that make sperm. While these tumours typically start in the testicles they can also occasionally arise in the abdomen, chest, or other areas of the body, even if there’s no evidence of cancer in or near the testicles.
Two of the most common germ cell tumours are seminoma and non-seminoma.
- Seminomas make up about half of all germ cell tumours. They usually grow slowly. Early-stage seminomas can often be cured because they’re less likely to metastasise (spread) to other parts of the body.
- Non-seminomas are often more aggressive than seminomas, and more likely to spread beyond the testicle.
About 5 percent of testicular cancers start in stromal cells, which make testosterone. However, testicular stromal tumors are often benign (not cancerous). A stromal cell tumor could also be a cancer that has spread from another part of the body (called a secondary cancer).