There are many different causes of testicular lumps and swellings. Testicular cancer is a possible cause. About 2,000 cases of testicular cancer are diagnosed in the UK every year. However, less than 4 in 100 lumps are testicular cancer.
The main types of lumps and their causes are explained below.
Varicoceles
The exact cause of varicoceles is unknown. However, most experts believe that they are caused by abnormalities in the veins in the testicles. There may be a blockage in the veins, or a problem with the valves in the veins. The valves are flaps that prevent blood flowing in the wrong direction.
The abnormal veins do not circulate blood as efficiently as normal veins. This leads to a build-up of excess blood in the veins, which makes them swell.
During puberty (when the body matures sexually), blood flow increases to the testicles and they grow larger. This can make varicoceles more noticeable.
Hydroceles
During pregnancy, a male baby's testicles develop inside his abdomen (tummy). Once they have formed, the testicles pass down through a passage and into the scrotum (the loose sac of skin that contains the testicles).
Usually, the passage closes before birth but, in some cases, it stays open. If the passage remains open, fluid can pass from the abdomen into the scrotum, causing the swelling that is associated with a hydrocele.
In most cases, the fluid is absorbed into the surrounding tissue during the child's first year or two of life, and the hydrocele disappears.
Hydroceles that develop in men or older boys may be indicated by inflammation (redness and swelling) of the scrotum, which is caused by:
- an injury
- an infection
- a tumour (growth)
Epididymal cysts
The epididymis is a coil-like structure behind the testicles that helps to store and transport sperm. Sometimes, a fluid-filled swelling can appear on the epididymis, although the cause is usually unknown.
People who have certain conditions that affect their kidneys may be at increased risk of developing epididymal cysts. For example, autosomal dominant polycystic kidney disease (ADPKD) is a genetic condition that causes multiple cysts to develop on the kidneys.
Testicular torsion
The testicles hang from a cord known as the spermatic cord. The spermatic cord should be loose enough to allow the testicles some movement within the scrotum but not so loose that they can move too freely.
Some boys are born with a spermatic cord that is too loose. This means that there is an increased risk of a testicle moving too much and twisting the spermatic cord as a result.
If a spermatic cord becomes severely twisted, the main blood supply for the affected testicle can be interrupted. This is a dangerous situation. If not treated immediately, the testicle may die. Immediate surgery is needed to untwist the cord, restore the blood supply and save the testicle.
Testicular torsion is most common among boys aged 13-17, although it can also occur in:
- men in their 20s
- unborn babies in the womb
- newborn babies
Testicular torsion can sometimes occur if there is trauma to the testicle, such as in an accident. However, most cases happen for no apparent reason. Testicular torsion may be more likely if you have:
- a tumour (growth) in your testicles
- a history of undescended testicles (where a boy is born without one or both testicles in their scrotum)
Other causes
Other causes of testicular lumps or swellings include:
- epididymitis – inflammation of the epididymis, which may be caused by a sexually transmitted infection or a urinary tract infection
- epididymo-orchitis – epididymitis (see above) combined with orchitis (inflammation of the testicle), which is usually due to an infection
- an inguinal hernia – a piece of your bowel pokes through a weakness in the muscle or surrounding tissue wall into your groin; more than a quarter of men will have an inguinal hernia during their lifetime
