The testicles are sometimes called the testes. They’re two small, oval-shaped organs, contained in a sac of skin called the scrotum, which hangs below the penis.
From puberty, the collecting tubules inside the testicles produce sperm, which can fertilize a female egg. The testicles are the main organs of the male reproductive system.
The structure of the testicle
The tubules form a coiled tube called the epididymis. This feels like a soft swelling at the back of the testicle. The epididymis carries on to the outside of the testicle and widens to become the spermatic cord (vas deferens).
This joins to the ejaculatory duct where sperm is ejaculated out of the penis. Sperm is mixed with fluid from the prostate and seminal vesicles (small tubular glands near the prostate) before it is ejaculated from the penis. The ejaculated fluid and sperm are called semen.
The male reproductive system
The testicles also produce the hormone testosterone. Hormones are chemical messengers that help to control different activities in our bodies. Testosterone is responsible for:
- your sex drive (libido)
- getting an erection
- having a deep voice
- facial and body hair
- muscle development.
Sometimes cancer cells from the testicle can spread to nearby lymph nodes (also known as glands). Lymph nodes are small and round, and there are lots of them throughout the body. They’re connected to each other by a network of tiny lymphatic vessels that carry a fluid called lymph, which contains cells that help us fight infection. This is a part of our immune system − the body’s natural defense against infection.
Cancer cells can be picked up by the lymph fluid and carried to lymph nodes in other parts of the body. Lymph vessels in your testicles carry fluid to a collection of lymph nodes at the back of your tummy (abdomen). These lymph nodes are called the retroperitoneal lymph nodes. They lie just behind your bowel and in front of your spine. You’ll have a scan (CT scan) to check if any of these nodes are larger than normal.
Causes and risk factors
The causes of testicular cancer are unknown, but research is going on all the time to try to find out more.
There are factors that can increase the chance of getting testicular cancer:
Undescended testicle (known as cryptorchidism)
Usually, the testicles develop inside the abdomen of an unborn child and come down (descend) into the scrotum at birth or by the time the child is one year old. Sometimes the testicle doesn’t descend into the scrotum. In this case, surgery is carried out to bring the testicle down into the scrotum. Men who’ve had an undescended testicle as a child have a higher chance of getting testicular cancer.
Men with a brother or father who’ve had testicular cancer are slightly more at risk of getting it – although the risk is still small. Researchers have found one particular gene that may cause testicular cancer in some men. It’s possible that this gene is inherited. This may be why testicular cancer sometimes happens in brothers or sons of men who’ve had it. There may be other genes linked to testicular cancer, but these have not been found yet.
Carcinoma in situ (CIS)
These are abnormal cells in the testicle that, if left, can develop into testicular cancer. CIS tends to be found when men have a biopsy of the testicle to investigate infertility (inability to have children). The testicle with the CIS is usually removed.
Cancer in the other testicle
A small number of men who’ve previously been treated for testicular cancer will go on to develop a cancer in the other testicle.
Ethnicity and social status
Testicular cancer is more common in white men than African-Caribbean or Asian men. It’s also more common in wealthier social groups. The reason for this is unknown.
Men who are taller appear to have a higher risk of testicular cancer, but it’s not clear why.
Human Immunodeficiency Virus (HIV)
Men infected with HIV have an increased risk of developing testicular cancer, particularly seminoma.
Sometimes an injury to a testicle or the groin may bring a testicular cancer to your doctor’s attention. But there’s no evidence to suggest that injury to a testicle increases your risk of getting cancer. Having a vasectomy doesn’t increase the risk of getting testicular cancer either.
Testicular cancers are also called germ cell tumors (GCTs). Germ cells in men produce sperm, so these tumors usually develop in the testicles. We use the term testicular cancer for all types of testicular tumors.
If your specialist thinks you have testicular cancer they will organize an operation to remove your testicle. After this operation, the tissue is examined under the microscope to find out the type of testicular cancer you have. There are two main types:
These usually occur in men between the ages of 25 and 55. About 40-45% of (4-4.5 in 10) men with testicular cancer have a seminoma.
Non-seminomatous germ cell tumors (NSGCTs)
This group of tumors are sometimes called teratomas. NSGCTs usually affect younger men aged between 15-35 years old. They occur in about 40-45% of (4-4.5 in 10) men with testicular cancer. NSGCTs include different types of tumors, such as teratomas and embryonal tumors. Many are a mixture of these types and other tumors, including seminomas. Although there are some minor differences, these tumors behave and are treated in similar ways.
Sometimes, a type of cancer called non-Hodgkin lymphoma can occur in the testicles. Other rare types are Leydig and Sertoli cell tumors.