Causes. Scrotal masses can be caused by a number of complications and disorders. While testicular cancer is one of the most common, finding a lump in the scrotum should not be self-diagnosed as such. Testicular cancer tumors usually present as a non-tender lump. While they can cause a certain degree of swelling and/or pain, many men with tumors do not experience other symptoms. A scrotal mass may also be a spermatic cyst, which is a fluid-filled, noncancerous sac. Other conditions, such as epididymitis and orchitis, are infections known to cause masses at times, as is hydrocele, which occurs when there is an excess of fluid in the sacs surrounding the testicles, often after an injury. Inguinal hernias are yet another cause of scrotal masses.