The testicles are part of the male reproductive system. They are also called testes (or a testis, if referring to one).
Testicles are two small, egg-shaped glands that sit behind the penis in a pouch of skin known as the scrotum.
The job of the testicles is to produce and store sperm. They also produce the male hormone called testosterone, which is responsible for the development of male characteristics such as facial hair growth, a deep voice, muscle development, sexual drive (libido), and the ability to have an erection.
A structure called the epididymis is attached to the back of each testis. The epididymis stores immature sperm and is attached to the spermatic cord, a tube which runs from each testicle through the groin region into the abdominal cavity. The spermatic cord contains blood vessels, nerves, lymph vessels and a tube called the vas deferens, which carries sperm to the prostate gland.
The prostate gland produces fluid which, along with sperm from the testicles, makes up a large part of semen. Semen is ejaculated from the penis during sexual climax.
There are many lymph nodes (glands) and lymphatic vessels around the testicles and in the abdomen. These are part of the lymphatic system and are important for resisting and fighting disease (immunity). The nodes and vessels also drain lymphatic fluid (lymph) from the tissues back into the bloodstream.
Cancer that develops in a testicle is called testicular cancer or cancer of the testis. Usually only one testicle is affected, but in some cases both testicles are affected. Most testicular cancers start in the cells that develop into sperm, which are called germ cells.
Sometimes testicular cancer can spread to lymph nodes in and around the testicles and abdomen, or to other parts of the body.
The most common testicular cancers are called germ cell tumours. There are two main groups, which look different under a microscope:
Sometimes a testicular cancer can include a mix of seminoma cells and non-seminoma cells, or a combination of the different types of non-seminoma. When there are seminoma and non-seminoma cells mixed together, doctors treat it as a non-seminoma cancer.
A small number of testicular tumours start in cells that make up the supportive (structural) and hormone-producing tissue of the testicles. These are called stromal tumours. The two main types are Sertoli tumours and Leydig cell tumours. They are usually benign and are removed by surgery.
Other types of cancer, such as lymphoma, can also involve the testis. For information, call Cancer Council 13 11 20.
Some germ cell cancers begin as a condition known as intratubular germ cell neoplasia (ITGCN) or carcinoma in situ (CIS). This is a non-invasive precursor to testicular cancer, because the cells are abnormal, but haven’t spread outside of the area where the sperm cells develop.
There is about a 50% risk that ITGCN will progress into testicular cancer within a five-year period.
ITGCN is difficult to diagnose because there are no symptoms and it can only be found by biopsy. However, about 5–10% of men diagnosed with testicular cancer had ITGCN.
ITGCN has similar risk factors to testicular cancer – see below.
The causes of testicular cancer are unknown, but certain factors may increase a man’s risk of developing it:
Men who have previously had testicular cancer in one testicle are about 25 times more likely to develop cancer in the other testicle. ITGCN is also a risk factor (see above).
Sometimes gene mutations are passed on in families. A man with a father or brother who has had testicular cancer is slightly more at risk. However, family history is only a factor for about 2% of patients.
If you are concerned about your family history of testicular cancer, you may choose to ask your doctor for a referral to a family cancer clinic, genetic counsellor and/or urologist. They can provide information on the most suitable screening for you and your family members.
Before birth, testicles develop inside a male baby’s abdomen. By birth, or within the first year of life, the testicles usually move down into the scrotum.
If the testicles don’t descend by themselves, doctors perform an operation to bring them down. Although this reduces the risk of developing testicular cancer, men born with undescended testicles are still about 16 times more likely to develop testicular cancer than men born with descended testicles.
Having difficulty conceiving a baby (infertility) is associated with ITGCN (see above), undescended testes and genetic abnormalities. Due to the shared risk factors with testicular cancer, infertility is also considered a risk factor for testicular cancer.
There is some evidence that men with HIV have an increased risk of testicular cancer. This is thought to be associated with the body’s impaired immune system and not being able to monitor for cancer cells.
Some men are born with an abnormality of the penis called hypospadias. This causes the urethra to open on the underside of the penis, rather than at the end. Men with this condition are about twice as likely to develop testicular cancer.
There is no known link between testicular cancer and injury to the testicles, sporting strains, hot baths, wearing tight clothes, sexual activity or having a vasectomy.
About 740 men are diagnosed with testicular cancer each year, accounting for about 1% of all cancers in Australian men. It occurs most often in men aged 20–40 years, and the average age at diagnosis is 35.
In some men, testicular cancer does not cause any noticeable symptoms. Other men may notice one or more of these symptoms:
These symptoms don’t necessarily mean you have testicular cancer. They are common to other conditions, such as cysts, which are harmless lumps. However, if you have any of these symptoms, you should have them checked by your doctor without delay.
Reviewed by: Dr Peter Heathcote, Senior Urologist, Princess Alexandra Hospital, QLD; Gregory Bock, Cancer Nurse Coordinator Urology, WA Cancer and Palliative Care Network, WA; A/Prof Martin Borg, Radiation Oncologist, Adelaide Radiotherapy Centre, SA; A/Prof Howard Gurney, Head of Clinical Research for Medical Oncology, Westmead Hospital, Director of Clinical Trials and Medical Oncology, Macquarie University, NSW; Carmen Heathcote, Cancer Council Queensland Helpline Operator, QLD; Aaron Likely, Consumer; David Moser, Consumer; and Dr Marketa Skala, Radiation Oncologist, W.P. Holman Clinic, TAS.