A benign testicular swelling is basically a swelling in your testicles, which may slowly get larger over time. Cancers are normally rock hard, whereas these normally feel slightly soft to touch. They do not progress to cancer.
The swelling can be due to a number of things, but the two most common causes are a hydrocele and an epididymal cyst. A hydrocele is collection of fluid around the testes. It lies within a sac called the tunica vaginalis, which is cut open if an operation is done to fix the swelling. An epididymal cyst is a cyst that grows out of the tube that takes sperm from the testes to the vas. Sometimes the veins in the scrotum become enlarged, much like a varicose vein, this is known as a varicocoele. A varicocoele usually occurs on the left-hand side and is often described as a 'bag of worms'. They are more obvious when standing up, such as in the shower.
Though it is common to do ultrasounds on the scrotum, the doctor can usually diagnose your condition based on how the lump feels and by shining a light through the fluid collection. A bright light should pass through the hydrocele or epididymal cyst.
If the lumps are small, they should be left alone. If they are medium-sized, then they can be drained. Sometimes, the lump will return after draining so a fluid is used to 'fill' up the sac. A second treatment may be needed. If the lump is large, then surgery is probably the best option. If the lump is a varicocoele, there are many treatments, which aim to block off the vein.