Cancer is the general name for a group of more than 100 diseases. Although there are many kinds of cancer, all cancers start because abnormal cells grow out of control. Untreated cancers can cause serious illness and death.
Normal cells in the body
The body is made up of trillions of living cells. Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person’s life, normal cells divide faster to allow the person to grow. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.
How cancer starts
Cancer starts when cells in a part of the body start to grow out of control. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into) other tissues, something that normal cells cannot do. Growing out of control and invading other tissues are what makes a cell a cancer cell.
Cells become cancer cells because of DNA (deoxyribonucleic acid) damage. DNA is in every cell and it directs all the cell’s actions. In a normal cell, when DNA gets damaged the cell either repairs the damage or the cell dies. In cancer cells, the damaged DNA is not repaired, and the cell doesn’t die like it should. Instead, the cell goes on making new cells that the body doesn’t need. These new cells all have the same abnormal DNA as the first cell does.
People can inherit abnormal DNA, but most DNA damage is caused by mistakes that happen while the normal cell is reproducing or by something in the environment. Sometimes the cause of the DNA damage may be something obvious like cigarette smoking or sun exposure. But it’s rare to know exactly what caused any one person’s cancer.
In most cases, the cancer cells form a tumor. Some cancers, like leukemia, rarely form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues where they grow.
How cancer spreads
Cancer cells often travel to other parts of the body where they begin to grow and form new tumors. This happens when the cancer cells get into the body’s bloodstream or lymph vessels. Over time, the tumors replace normal tissue. The process of cancer spreading is called metastasis.
How cancers differ
No matter where a cancer may spread, it’s always named for the place where it started. For example, breast cancer that has spread to the liver is called metastatic breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is called metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently. For instance, lung cancer and skin cancer are very different diseases. They grow at different rates and respond to different treatments. This is why people with cancer need treatment that is aimed at their kind of cancer.
Tumors that are not cancer
Not all tumors are cancer. Tumors that aren’t cancer are called benign. Benign tumors can cause problems – they can grow very large and press on healthy organs and tissues. But they cannot grow into (invade) other tissues. Because they can’t invade, they also can’t spread to other parts of the body (metastasize). These tumors are almost never life threatening.
How common is cancer?
Half of all men and one-third of all women in the US will develop cancer during their lifetimes.
Today, millions of people are living with cancer or have had cancer. The risk of developing many types of cancer can be reduced by changes in a person’s lifestyle, for example, by staying away from tobacco, limiting time in the sun, being physically active, and healthy eating.
There are also screening tests that can be done for some types of cancers so they can be found as early as possible – while they are small and before they have spread. In general, the earlier a cancer is found and treated, the better the chances are for living for many years.
Signs and Symptoms of Cancer - What are signs and symptoms?
Signs and symptoms are both signals of injury, illness, disease, or that something is not right in the body.
A sign is a signal that can be seen by someone else—maybe a loved one, or a doctor, nurse, or other health care professional. For example, fever, fast breathing, and abnormal lung sounds heard through a stethoscope may be signs of pneumonia.
A symptom is a signal that is felt or noticed by the person who has it, but may not be easily seen by anyone else. For example, weakness, aching, and feeling short of breath may be symptoms of pneumonia.
Having one sign or symptom may not be enough to figure out what’s causing it. For example, a rash in a child could be a sign of a number of things, such as poison ivy, measles, a skin infection, or a food allergy. But if the child has the rash along with other signs and symptoms like a high fever, chills, achiness, and a sore throat, then a doctor can get a better picture of the illness. Sometimes, a patient’s signs and symptoms still don’t give the doctor enough clues to be sure what is causing the illness. Then medical tests, such as x-rays, blood tests, or a biopsy may be needed.
How does cancer cause signs and symptoms?
Cancer is a group of diseases that can cause almost any sign or symptom. The signs and symptoms will depend on where the cancer is, how big it is, and how much it affects the organs or tissues. If a cancer has spread (metastasized), signs or symptoms may appear in different parts of the body.
As a cancer grows, it can begin to push on nearby organs, blood vessels, and nerves. This pressure causes some of the signs and symptoms of cancer. If the cancer is in a critical area, such as certain parts of the brain, even the smallest tumor can cause symptoms.
But sometimes cancer starts in places where it will not cause any signs or symptoms until it has grown quite large. Cancers of the pancreas, for example, usually do not cause symptoms until they grow large enough to press on nearby nerves or organs (this causes back or belly pain). Others may grow around the bile duct and block the flow of bile. This causes the eyes and skin to look yellow (jaundice). By the time a pancreatic cancer causes signs or symptoms like these, it’s usually in an advanced stage. This means it has grown and spread beyond the place it started—the pancreas.
A cancer may also cause symptoms like fever, extreme tiredness (fatigue), or weight loss. This may be because cancer cells use up much of the body’s energy supply, or they may release substances that change the way the body makes energy from food. Or the cancer may cause the immune system to react in ways that produce these signs and symptoms.
Sometimes, cancer cells release substances into the bloodstream that cause symptoms which are not usually linked to cancer. For example, some cancers of the pancreas can release substances that cause blood clots in veins of the legs. Some lung cancers make hormone-like substances that raise blood calcium levels. This affects nerves and muscles, making the person feel weak and dizzy.
How are signs and symptoms helpful?
Treatment works best when cancer is found early—while it’s still small and is less likely to have spread to other parts of the body. This often means a better chance for a cure, especially if the cancer can be removed with surgery.
A good example of the importance of finding cancer early is melanoma skin cancer. It can be easy to remove if it has not grown deep into the skin. The 5-year survival rate (percentage of people who live at least 5 years after diagnosis) at this stage is around 97%. Once melanoma has spread to other parts of the body, the 5-year survival rate drops below 20%.
Sometimes people ignore symptoms. Maybe they don’t know that the symptoms could mean something is wrong. Or they might be frightened by what the symptoms could mean and don’t want to get or can’t afford to get medical help. Some symptoms, such as tiredness or coughing, are more likely caused by something other than cancer. Symptoms can seem unimportant, especially if there’s an obvious cause or the problem only lasts a short time. In the same way, a person may reason that a symptom like a breast lump is probably a cyst that will go away by itself. But no symptom should be ignored or overlooked, especially if it has lasted a long time or is getting worse.
Most likely, any symptoms you may have will not be caused by cancer, but it’s important to have them checked out, just in case. If cancer is not the cause, a doctor can help figure out what is and treat it, if needed.
Sometimes, it’s possible to find cancer before you have symptoms. The American Cancer Society and other health groups recommend cancer-related check-ups and certain tests for people even though they have no symptoms. This helps find certain cancers early, before symptoms start. For more information on early detection tests, see our document American Cancer Society Guidelines for the Early Detection of Cancer. But keep in mind, even if you have these recommended tests, it’s still important to see a doctor if you have any symptoms.
What are some general signs and symptoms of cancer?
You should know some of the general signs and symptoms of cancer. But remember, having any of these does not mean that you have cancer—many other things cause these signs and symptoms, too. If you have any of these symptoms and they last for a long time or get worse, please see a doctor to find out what’s going on.
Most people with cancer will lose weight at some point. When you lose weight for no known reason, it’s called an unexplained weight loss. An unexplained weight loss of 10 pounds or more may be the first sign of cancer. This happens most often with cancers of the pancreas, stomach, esophagus (swallowing tube), or lung.
Fever is very common with cancer, but it more often happens after cancer has spread from where it started. Almost all patients with cancer will have fever at some time, especially if the cancer or its treatment affects the immune system. (This can make it harder for the body to fight infection.) Less often, fever may be an early sign of cancer, such as blood cancers like leukemia or lymphoma.
Fatigue is extreme tiredness that does not get better with rest. It may be an important symptom as cancer grows. It may happen early, though, in some cancers, like leukemia. Some colon or stomach cancers can cause blood loss that’s not obvious. This is another way cancer can cause fatigue.
Pain may be an early symptom with some cancers like bone cancers or testicular cancer. A headache that does not go away or get better with treatment may be a symptom of a brain tumor. Back pain can be a symptom of cancer of the colon, rectum, or ovary. Most often, pain due to cancer means it has already spread (metastasized) from where it started.
Along with cancers of the skin, some other cancers can cause skin changes that can be seen. These signs and symptoms include:
Darker looking skin (hyperpigmentation)
Yellowish skin and eyes (jaundice)
Reddened skin (erythema)
Excessive hair growth
Signs and symptoms of certain cancers
Along with the general symptoms, you should watch for certain other common signs and symptoms that could suggest cancer. Again, there may be other causes for each of these, but it’s important to see a doctor about them as soon as possible.
- Change in bowel habits or bladder function
Long-term constipation, diarrhea, or a change in the size of the stool may be a sign of colon cancer. Pain when passing urine, blood in the urine, or a change in bladder function (such as needing to pass urine more or less often than usual) could be related to bladder or prostate cancer. Report any changes in bladder or bowel function to a doctor.
Skin cancers may bleed and look like sores that don’t heal. A long-lasting sore in the mouth could be an oral cancer. This should be dealt with right away, especially in people who smoke, chew tobacco, or often drink alcohol. Sores on the penis or vagina may either be signs of infection or an early cancer, and should be seen by a health professional.
- White patches inside the mouth or white spots on the tongue
White patches inside the mouth and white spots on the tongue may be leukoplakia. Leukoplakia is a pre-cancerous area that’s caused by frequent irritation. It’s often caused by smoking or other tobacco use. People who smoke pipes or use oral or spit tobacco are at high risk for leukoplakia. If it’s not treated, leukoplakia can become mouth cancer. Any long-lasting mouth changes should be checked by a doctor or dentist right away.
- Unusual bleeding or discharge
Unusual bleeding can happen in early or advanced cancer. Coughing up blood in the sputum (phlegm) may be a sign of lung cancer. Blood in the stool (which can look like very dark or black stool) could be a sign of colon or rectal cancer. Cancer of the cervix or the endometrium (lining of the uterus) can cause abnormal vaginal bleeding. Blood in the urine may be a sign of bladder or kidney cancer. A bloody discharge from the nipple may be a sign of breast cancer.
- Thickening or lump in the breast or other parts of the body
Many cancers can be felt through the skin. These cancers occur mostly in the breast, testicle, lymph nodes (glands), and the soft tissues of the body. A lump or thickening may be an early or late sign of cancer and should be reported to a doctor, especially if you’ve just found it or notice it has grown in size. Keep in mind that some breast cancers show up as red or thickened skin rather than the expected lump.
- Indigestion or trouble swallowing
Indigestion or swallowing problems that don’t go away may be signs of cancer of the esophagus (the swallowing tube that goes to the stomach), stomach, or pharynx (throat). But like most symptoms on this list, they are most often caused by something other than cancer.
- Recent change in a wart or mole or any new skin change
Any wart, mole, or freckle that changes color, size, or shape, or that loses its sharp border should be seen by a doctor right away. Any other skin changes should be reported, too. A skin change may be a melanoma which, if found early, can be treated successfully.
- Nagging cough or hoarseness
A cough that does not go away may be a sign of lung cancer. Hoarseness can be a sign of cancer of the voice box (larynx) or thyroid gland.
The signs and symptoms listed above are the more common ones seen with cancer, but there are many others that are not listed here. If you notice any major changes in the way your body works or the way you feel – especially if it lasts for a long time or gets worse – let a doctor know. If it has nothing to do with cancer, the doctor can find out more about what’s going on and, if needed, treat it. If it is cancer, you’ll give yourself the chance to have it treated early, when treatment works best.