Hesperian Health Guides


What is Cancer?
woman looking through a microscope.
Cells are so small, you can only see them with a microscope.

Our bodies, and all living things, are made of cells. Cells are tiny units of different types that, working together, make a living thing. Each cell is also alive. It divides to make new cells, and each one eventually dies.

Sometimes a new cell forms the wrong way and is not healthy. Usually this causes no harm to the body as a whole, because it is just one tiny cell of millions, and it soon dies. But sometimes a damaged cell divides and creates more and more cells just like it. These damaged cells reproduce and form an unhealthy mass or growth in the body called a tumor.

A tumor can be benign, meaning it does not spread or cause damage. Or it can be malignant, meaning it keeps growing and invades other parts of the body. This is cancer. Depending on the types of cells and where they grow, cancer can be slow-growing and harmless, or can cause severe sickness or death.

Cancer is not one disease. Every type of cancer is different. Some can be prevented, and some are easily treated and even cured. Others are deadly.

If you are worried you might have cancer

a woman talking to a man.
It could be cancer — or it could be a simple infection!

Thinking you might have cancer can be very worrisome. Do not delay in seeking help for a sign that could mean cancer, but stay calm and remember that many cancer signs are also signs of other, less serious problems.

For most cancers, the only sure way to know you have it is with a surgical test called a biopsy which is available at some clinics and hospitals. During a biopsy, a health worker removes a very small piece of the body where cancer is suspected and examines it under a microscope to look for abnormal cells.

If a new lump is growing or causing pain, under your skin or anywhere in your body, it should be examined. This is especially important if it is firm and does not move. A lump could be an infection or a bump that is harmless and will go away by itself, but it also could be a sign of cancer, one that is possible to find early and treat. Ask a health worker about a lump that:

a man with lumps on his neck and groin.
  • grows in size
  • is new and does not go away in a few weeks
  • causes pain
  • feels hard

The body fights infection through the lymph system, but lymph glands can also be a place where cancer develops. See a health worker about swelling or lumps that do not go away, especially:

  • behind the ear
  • on the neck or under the chin
  • in the armpits and groin

If a person has a lump for many years that does not grow or change, it probably is not cancer.

There are signs common to many cancers, but not all cancers cause these signs. And all these signs can be caused by chronic health problems that are not cancers. In this chapter, read about the signs specific to:

Signs common to many cancers

In general, these signs happen when cancer is advanced, so they are not good signs to rely on for finding cancers early.

a woman in the waiting room of a cancer screening clinic. Sign says "Breast cancer screening every afternoon."
Cancer screenings save lives. They should be available to everyone.
  • Weight loss
  • Feeling tired all the time (fatigue)
  • Severe pain that does not get better

If you think you might have cancer, find a health worker who can help you understand what options are available for treatment or care and where to go. Bring another person with you during appointments to help you ask questions and remember information.

Screening programs

Some cancers can be found early, before they cause any signs, through screening programs which test people at risk for certain types of cancer. Screening programs are most common for cervical cancer and breast cancer because it is possible to detect these cancers before they cause harm, and these cancers can often be successfully treated when found early.

The earlier a cancer is found, the greater the chance for successful treatment.

Who gets cancer?

We know a lot about what causes cancer, but not always why some people get cancer and others do not. Anyone can get cancer and chances increase as you get older. For only a few types of cancer (especially breast cancer), having one person in the family with that cancer makes it more likely that another person will too. But most cancers do not “run in the family.” We do know:

  • Magic spells, curses, or the evil eye do not cause cancer.
  • Birth control methods do not cause cancer.
  • Cancer is not a punishment for having done something wrong.
  • Cancer does not spread from one person to another — it is impossible to get cancer from being near, spending time with, or taking care of someone who has cancer.

Some activities like cigarette smoking do cause cancer. Some chemicals that get into our bodies at work or through foods, products we use, and from air or water pollution cause cancer. There are ways to prevent cancers but there are many things that cause cancer that individuals have little control over. Even when 2 people are exposed to the same harmful things, it does not mean they will both get cancer.

Because cancer and its causes can seem mysterious, people with cancer are sometimes avoided or treated poorly by others. This can make their illness worse. People with cancer need our love and support.

This page was updated:25 Nov 2019