What are the testicles?

The testicles (or testes, singular testis) are two small organs found inside the scrotum, the pouch of skin under the penis. 

They are part of the male reproductive system and are responsible for making sperm, as well as producing testosterone, the important hormone during male development and maturation. Testosterone also aids the development of muscles, deepening of the voice and growth of body hair and libido.  

It’s normal for one testicle to be lower than the other. It’s nature’s way of allowing you to cross your legs without screaming!

About cancers

Cancer is a group of more than 100 diseases. Although each kind differs from the others in many ways, every type of cancer is a disease of some of the body’s cells. In our case, we call it testicular cancer, but as many as 14 different types of cancer can start in the testicle.

Healthy cells that make up the body’s tissues grow, divide, and replace themselves in an orderly way. This process keeps the body in good repair. Sometimes, however, some cells lose the ability to limit and direct their growth. They grow too rapidly and without any order. Too many cells are produced, and tumours are formed. Tumours can be either benign or malignant.

Benign tumours are not cancer. They do not spread to other parts of the body and are seldom a threat to life. Benign tumours can often be removed by surgery, and they are not likely to return. Some tumours of the testicle are benign, but most are not.

Malignant tumours are cancer. They can invade and destroy nearby healthy tissues and organs. Cancerous cells can also spread, or metastasise, to other parts of the body and form new tumours.


Testicular Cancer

Testicular cancer occurs when abnormal cells develop in the testes. Usually only one testicle is affected, but sometimes both. About 90-95% of testicular cancers start in the cells that develop into sperm – known as germ cells.

Compared to other types of cancer, testicular cancer is rare. But it is the most common cancer is young men aged 18-39 years (excluding non-melanoma skin cancer).

In New Zealand, about 150 men are diagnosed and 7-10 men die each year from testicular cancer.

Types of testicular cancer.

When testicular cancer cells are viewed under the microscope there are two main types: seminoma and non-seminoma cells, which are quite different when observed. 

  • Seminoma cells usually occur in men aged 25-45 but can also occur in men over 60, or at any age. This form of testicular cancer develops more slowly and is usually confined to the testes but lymph nodes may also be involved.
  • Non-Seminona cells are faster developing and will spread to other parts of the body. This type occurs more often in younger men in their late teens and early 20s.

Testicular cancer is very treatable even when the cancer has spread beyond the testicle to other parts of the body. The 5-year survival rate for me diagnosed with testicular cancer if over 95%.


A number of symptoms may indicate possible testicular cancer. The most common is a painless swelling or lump in the testicle. Other less common symptoms include: 

  • Any enlargement of a testicle
  • A significant shrinking of a testicle
  • A change in the consistency of a testicle (hardness)
  • A feeling of heaviness in the scrotum
  • A dull ache in the lower abdomen or in the groin
  • A sudden collection of fluid in the scrotum
  • Pain or discomfort in a testicle or in the scrotum
  • Enlargement or tenderness of the breasts

These symptoms are not sure signs of cancer, they can also be caused by other conditions. It is very important to see a doctor when noticing any of these signs or symptoms. It may not be cancer but needs to be checked out. 

Risk Factors

While the definite causes are still unknown, these are some of the risk factors: 

  • An undescended testicle as an infant 
  • Family history of testicular cancer
  • Abnormal testicular development 

There is no known link between testicular cancer and injury to the testicles, hot baths, wearing tight clothing or sporting strains. 

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