In the United States, there are about 10,000 new cases of testicular cancer each year. The average age of diagnosis is 33 years old, and it's the most common cancer in men between the ages of 20 and 40. However, testicular cancer can occur at any age, with about 6% of cases in children and teens, and about 7% in men over 55.
How serious testicular cancer is depends on the type of testicular cancer, how big it is and if it has spread.
The first sign of testicular cancer often is a bump or lump on a testicle. The cancer cells can grow quickly and they often spread outside the testicle to other parts of the body.