It can be varicocele, which is a swelling in one or more of the veins that feed blood to your testicles from the cords they hang dwon from inside your scrotum. they usually get bigger when you stand up for a while and get smaller when you lay down on your back for a while and the blood either accumulates or flows out leaving those veins full or normal. You also have an epididymis on the back side of each testicle which stores sperm made inside your testicles. These feel like a lumpy cord or band from the top to bottom of each testicle on the back side toward the anus. these fill and shrink when you ejaculate sperm and store it between ejaculations. The head of each epididymis can get tiny swellings called spermiceles that are common and harmless. Many men and boys also have small scarred lumps on their testicle cords from past injuries like testicles hits during sports and work. Most of these are common and harmless also. Your testicles and scrotum cords can be tougher than you think. Ask a Dr. or nurse to take a look the next time your have a yearly physical or sports exam. Testicular cancers are located right on the testicle surface itself or growing inside the testicle ball and not hanging in the sack above and separate from the testicles.