While many men who experience testicular swelling worry about cancer, the disease is relatively uncommon (about 9,310 U.S. cases predicted in 2018). Testicular cancer is a young man’s disease, usually developing between ages 15 and 40. The cause is unknown, but cancer is 11 times more likely to develop in a testicle that has not descended into the scrotum by the time of birth than a testicle that descends normally (during the 32nd week of fetal life). Testicular cancer usually produces a hard lump in one testicle. Sometimes, however, the entire testicle is enlarged and abnormally firm. The disease is generally painless, but some men notice a dull ache or heavy feeling. Detected early, testicular cancer is highly curable.
P.S. The average age at the time of diagnosis of testicular cancer is about 33, but about six percent of cases occur in children and teens and about eight percent occur in men over age 55.