Are both testicles supposed to be most or less the same size? One of my balls is smaller than the other. Could this be a sign of cancer?
John (age 25)
Even though we have two eyes, two noses, two hands, etc., none is exactly alike between their left and right sides. While the sides generally are closely alike, they are not precisely alike, and this includes the testicles. Since you are past the adolescent years, your testicles should be between 16 and 27 ml. An orchidometer, a string of beads of varying sizes, is used to compare testicles sizes.
Most men have one testicle that is slightly smaller than the other. A large difference might indicate that one testicle is underdeveloped -- possibly due to damage that occurred during your early years before you finished developing. If such is the case, then it would mean the the small testicle is not producing as much sperm as the other. It would decrease your sperm count per ejaculation a bit, but it won't cause much other problems.
It is also possible that one side is larger because of swelling -- most often due to an infection. Generally the area will feel hot and there might be discomfort or even pain. Such should be examined by a doctor and treated to prevent damage to the testicle.
Testicular cancer is detected as a small, hard bump on the testicle, about the size of a pea. It should not be confused with the soft epididymis on the back of the testicle.