Most testicular lumps and swellings are caused by benign (non-cancerous) conditions, although occasionally they can be a symptom of testicular cancer.

It's important to see your GP if you notice a lump or swelling in one of your testicles so they can try to identify the cause and arrange any further tests if necessary. Read more about diagnosing testicular lumps and swellings.

Some of the main types of testicular lumps and swellings are outlined below.

Benign testicular lumps and swellings

There are a number of different benign causes of testicular lumps and swellings.

Most of these conditions are largely harmless and may not require treatment, although you should seek immediate medical advice if you suspect you have testicular torsion (see below) because it needs to be treated quickly.

Varicoceles

Varicoceles are soft lumps that usually develop gradually above the testicle and mostly on the left side of the scrotum (the loose sac of skin that contains the testicles). They are sometimes described as feeling like a "bag of worms".

The exact cause of varicoceles is not clear, but it is widely thought that they occur as the result of abnormalities in the veins in the testicles leading to a build-up of excess blood in the veins, which makes them swell.

The size of varicoceles can vary. Some may only be noticeable when you touch them. Others can be larger and seen easily. The side of the scrotum that contains the varicoceles may hang slightly lower than the other side.

Besides a lump, varicoceles do not usually cause any other symptoms, although some men who have them experience a heavy feeling or aching pain in their scrotum or groin.

In a few cases, varicoceles have been linked to infertility in men. However, there is no evidence that surgically removing them improves your chances of being able to father a baby.

Hydroceles

Hydroceles are swellings in the scrotum caused by a build-up of fluid.

They often affect newborn babies, usually only causing a painless swelling of one or both testicles, although they can sometimes affect older boys or men, who may feel some discomfort in the scrotum.

During pregnancy, a male baby's testicles develop inside his abdomen (tummy) and they pass down into the scrotum through a passage once they are formed. This passage usually 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 associated with a hydrocele.

In most cases affecting babies, 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 caused by inflammation (swelling) of the scrotum resulting from problems such as an injury or infection.

Epididymal cysts

An epididymal cyst is a small, smooth fluid-filled swelling that slowly develops in the epididymis (a coil-like structure behind the testicles that helps to store and transport sperm).

They are often painless, but the affected testicle may sometimes ache or feel heavy. You may also experience some pain and discomfort if the cyst puts pressure on other structures in or around your testicle.

It's not clear what causes epididymal cysts, but they tend to be more common in middle-aged men.

Epididymo-orchitis

Epididymo-orchitis is the inflammation of the epididymis as well as the testicle, causing the affected testicle to become swollen, painful and tender over a matter of hours or days.

It's not always clear what causes epididymo-orchitis, but the condition is often linked to an infection, including:

• sexually transmitted infections (STIs), such as chlamydia and gonorrhoea
• urinary tract infections (UTIs)
• mumps

Epididymo-orchitis can sometimes lead to a reduced sperm count in affected men, although this is rarely significant enough to cause infertility.

Inguinal hernias

An inguinal hernia occurs when fatty tissue or a part of your bowel, such as the intestine, pokes through into your groin at the top of your inner thigh.

The hernia can appear as a swelling or lump in your groin, or as an enlarged scrotum. The lump is often painless, but it can become suddenly and severely painful if the blood supply to the section of organ or tissue trapped in the hernia has become cut off (strangulation).

If you think you have a hernia that has become strangulated, you should visit your nearest accident and emergency (A&E) department as soon as possible because urgent surgery may be required.

Inguinal hernias occur when the tissue or bowel pushes through a weak spot in the surrounding muscle wall (the abdominal wall) into the inguinal canal. The inguinal canal is a channel through which blood vessels to the testicles pass in men and through which the round ligament (the ligament surrounding the womb) passes in women.

Inguinal hernias occur mainly in men. Most are thought to be due to ageing. This is because as you get older, the muscles surrounding your abdomen can become weaker. They can also sometimes appear suddenly due to strain on the abdomen, such as straining on the toilet if you have constipation or carrying and pushing heavy loads.

Testicular torsion

Testicular torsion is a benign but serious condition caused by the spermatic cord (the cord that supplies the testicles with blood) becoming severely twisted.

Unlike the other types of benign testicular lumps and swellings, testicular torsion is a medical emergency. You should contact your GP immediately or visit your nearest accident and emergency (A&E) department as soon as possible if you suspect you have testicular torsion.

Signs and symptoms of testicular torsion include:

• a sudden, severe pain in one of your testicles
• swelling of the scrotum
• nausea
• vomiting
• abdominal (tummy) pain

If the spermatic cord becomes severely twisted, the blood supply for the affected testicle can be interrupted. If this is not treated quickly with surgery, there is a risk of losing the affected testicle.

Testicular torsion can occur at any age, but is most common in boys aged 13-17 and is rare in men over 30. It can also affect newborn babies and even unborn babies in the womb.

Most cases happen for no apparent reason, although the problem can occur in boys who are born with an unusually loose spermatic cord and it can develop after an injury to the testicles.

You may also be at a higher risk of developing testicular torsion if you have a history of undescended testicles (where a boy is born without both testicles in their scrotum).

Testicular cancer

Although the vast majority of testicular lumps and swellings are benign, a lump in one of the testicles can sometimes be a sign of testicular cancer.

Cancer Research UK estimates that fewer than four in every 100 testicular lumps are caused by cancer.

Lumps associated with testicular cancer tend to develop slowly on the testicle itself (as opposed to the scrotum) are usually:

• painless (although some men do experience pain or discomfort)
• solid and firm
• not tender to touch

Unlike many other types of cancer, the risk of testicular cancer does not keep increasing as you get older. The condition is most often diagnosed in boys and men between the ages of 15 and 49 and is uncommon in men older than this.

Read more about the symptoms of testicular cancer.