Cancer Risks, Signs, Symptoms, Tests, Treatments, and More

Cancer is a broad term used to describe many different diseases. In general, cancer happens when abnormal cells in your body grow out of control and crowd out normal cells.

It can start almost anywhere. Cancer can stay in one spot, or it can metastasize — spread throughout your body. Some cancers grow slowly, while others grow quickly.

Most cancers are named for where they start in the body. For instance, “breast cancer” begins in your breast tissue.

Many cancers form solid tumors, which are growths of tissue. But blood cancers, such as leukemia, don’t generally grow as tumors; they stay in the form of individual cells. Tumors can be either malignant (cancerous) or benign (noncancerous).

Prevalence: Cancer Is a Common Disease

According to the National Cancer Institute, more than 1.6 million new cases of cancer are diagnosed in the United States each year. About 597,690 people die from some form of the disease annually. (1)

Data also shows that more than 38 percent of men and women will be diagnosed with a form of cancer at some point in their lives. (2)

Cancer is the second-leading cause of death in this country, after heart disease. (3)

Anyone can get cancer, but the risk goes up as you get older. Nearly 9 out of 10 cancers are diagnosed in people 50 years of age or older. (4)

The good news is that survival rates are improving for many types of cancer because of advances in screening and treatment.

The Gene Factor: How Cancer Happens

Cancer is a genetic disease, which means it’s caused by changes in genes that control the way cells grow and divide in your body.

These gene alterations, sometimes called “mutations” cause a variety of changes that can make a cell cancerous. Some mutations accelerate the pace at which a cell duplicates itself, others prevent cells from knowing when to stop dividing, and still others keep them from dying off as normal cells are supposed to do. When a cell has acquired enough of these mutations to interfere with the “rules” by which normal cells behave, it has become cancerous.

Mutations can be inherited at birth or acquired during your lifetime. Exposure to harmful substances, such as tobacco smoke or radiation, can damage your DNA and cause gene changes to occur. Other lifestyle factors, such as extensive sun exposure, can also lead to mutations.

Just because you’re born with a certain mutation doesn’t always guarantee that you’ll develop cancer. Only 5 to 10 percent of cancers are a direct result of a mutation inherited from a parent. (5) Usually, inherited and acquired mutations work together to cause cancer. For example, you might inherit a gene from your parents that makes you more likely to develop a certain type of cancer when you’re exposed to tobacco smoke.

Metastasis: When Cancer Spreads

Cancer can spread from the area it started to other places in your body. This is known as metastasis.

Metastatic cancer can affect many organs of your body, but it still has the same type of cancer cells as the original cancer. Doctors will name your cancer based on its primary location. So, pancreatic cancer that has spread to your liver is still known as pancreatic cancer.

Generally, metastatic cancer cells look the same as the cells of the original cancer when viewed under a microscope.

When cancer spreads, it becomes much harder for doctors to treat.

The Most Common Cancers Affecting Americans

Nonmelanoma skin cancer is the most common form of cancer, affecting about 3.3 million people in the United States each year. (6)

Breast cancer is next, followed by lung cancer and prostate cancer.

Other common cancers include:

• Colon and rectal cancer
• Leukemia
• Liver cancer
• Bladder cancer
• Endometrial cancer
• Kidney cancer
• Melanoma
• Non-Hodgkin lymphoma
• Pancreatic cancer
• Thyroid cancer

Cancers Start in a Variety of Different Tissues in the Body

Cancer can happen anywhere in your body. There are many types of cancers, and each type also has its own subtypes that doctors may approach differently.

Cancers are sometimes divided into categories, including the following:

Carcinomas These are the most common types. They’re formed by epithelial cells, which line the inside and outside surfaces of the body. Carcinomas can be divided into the following subcategories:

• Adenocarcinomas develop in epithelial cells that make fluids or mucus. Breast, colon, and prostate cancers are adenocarcinomas.
• Basal cell carcinomas start in the lower base layer of the skin.
• Squamous cell carcinomas form in epithelial cells that are just below the outer surface of the skin. Squamous cells also line organs, such as the intestines, stomach, bladder, lungs, and kidneys.
• Transitional cell carcinomas form in a type of tissue called transitional epithelium. Cancers of the bladder, ureters, or kidneys are sometimes transitional cell carcinomas.

Sarcomas Sarcomas form in the bone and soft tissues (muscles, blood vessels, fat, tendons, ligaments, or lymph vessels) of the body. Osteosarcoma is a common type of bone cancer. Soft-tissue sarcomas include Kaposi sarcoma, liposarcoma, and others.

Leukemias Cancers that begin in the blood-forming cells are leukemias. They don’t usually form tumors, but instead grow in blood and bone marrow.

Lymphomas Lymphomas are cancers that develop from normal lymphocytes, which are infection-fighting white blood cells that are part of your immune system. Hodgkin lymphoma and non-Hodgkin lymphoma are the two main types.

Melanomas These cancers begin in cells called melanocytes, which give your skin its color. Most of the time, melanomas form on the skin, but they can also develop in other areas, such as the eye.

Multiple Myelomas Multiple myeloma is a type of blood cancer that is derived from plasma cells, which are a type of immune cell.

Brain and Spinal Cord Tumors: These tumors form in the nervous system of the body.

Neuroendocrine Tumors They develop in cells that release hormones into your blood.

Carcinoid Tumors These are a type of neuroendocrine tumor that are usually found in the rectum and small intestine.

Germ Cell Tumors Germ cell tumors begin in the reproductive cells (egg or sperm) of your body.

Life With Cancer

Years ago, people with cancer didn’t survive long. Thanks to medical advances, the outlook has improved significantly in recent years.

Today, about 15 million people in the United States are living with cancer. (4)

In recent years, cancer awareness movements have brought attention to all different types of cancers. You may have seen or worn a cancer ribbon to support yourself or a loved one as part of a cancer campaign. These programs help raise much-needed funds for research and drug development.

Cancer is not one disease, but many. Each requires its own special care and its particular treatment strategy. But one thing about cancer is easy to understand: you are far better off not getting it in the first place.

How do you do that? By avoiding the risks. Doctors understand a good deal about what can cause cancer, and you should stay far away from those causes. First among them is smoking. It is a primary cause of lung cancer and of more than a dozen other cancers. And there are other causes: unhealthy diets, obesity, lack of exercise, excess alcohol, and sun exposure among others. Know and avoid the risk factors, and you can help prevent cancer.

Learn More About Cancer Risk and Prevention

Knowing the signs and symptoms of cancer can help you and your doctor make a speedy diagnosis so that the cancer can be treated early. And that can boost the chances that the treatment will be successful.

Indications of cancer include such things as unexplained weight loss, fever and night sweats, extreme fatigue, and unexplained bleeding. None of these signs should cause immediate concern; they don’t always mean you have cancer. Some of them can be caused by entirely unrelated ailments. But the more you know, and the sooner you see your doctor, the more likely you and your doctor can spot cancer indications and start treatment.

Learn More About Cancer Signs and Symptoms

Some cancers can begin to grow without any signs or symptoms apparent to you or your doctor. To find those cancers early, researchers have developed a variety of screening tools that can indicate the presence of cancer before it makes itself known.

Among the cancers for which screening is available are cancers of the breast, colon, rectum, lung, cervix, and prostate.

It’s important to keep in mind that screening and diagnosis are different. A positive result in a screening test does not mean you have cancer. But it often means that you need more tests to make a definitive diagnosis, one way or the other.

Learn More About Cancer Screening

If you turn up with positive results on a screening test, don’t panic! For some cancers, doctors have good diagnostic tools that can go beyond screening and tell you whether you do or do not have cancer.

Imaging is one common tool used to confirm suspicious findings during cancer screening, including CT scans, X-rays, MRIs, and mammograms, among others. Another is what’s known as endoscopy, in which doctors insert a tube into the body to take a careful look around and see if they can spot any tumors. And a third tool is the biopsy, in which doctors take a small sample of your tissue to look for cancer. Some of the tests are more accurate than others, but all of them can help make a diagnosis.

Learn More About Cancer Tests and Diagnosis

When cancer is diagnosed, you and your doctor are going to want to know how far the cancer has progressed. Did a diagnostic tool catch it early? Or is it at a late stage in which, perhaps, it has already started to spread throughout the body?

Stage 1 means cancer is present. Stage 2 and stage 3 mean the tumor has grown and started to spread into nearby tissues. Generally, stage 4 means it has spread to distant parts of the body. Each type of cancer has a distinct staging system, and interpreting cancer staging can be tricky. Your oncologist can explain what your stages mean.

Learn More About Cancer Stages

Oncologists have a broad and growing selection of treatments they can now use to fight cancer. Many cancer patients can expect to receive a combination of treatments, depending on the kind of cancer they have and what stage it is at.

Surgery can be used to cut out tumors, and chemotherapy and radiation can be used to kill cancer cells; sometimes patients receive all three of these treatment approaches.

Immunotherapy is a newer treatment option in which the therapy increases the ability of the body’s immune cells to better recognize and attack cancer cells. Another newer treatment is targeted therapy, in which doctors directly attack genes or chemical pathways that spur cancer growth. New immunotherapies and targeted therapies are being developed every year.

Learn More About Cancer Treatment

As anyone who has undergone cancer treatment can tell you, the therapy can often be tough to endure, and can sometimes cause dangerous side effects. Treating those symptoms can improve the lives of patients while they and their doctors are trying to get rid of their cancer. Such treatment is referred to as palliative care, or supportive care. The treatments include medication, emotional support, relaxation techniques, nutritional support, and more. This kind of care can be important for children, too, as well as adults.

Learn More About Palliative Care

The Takeaway

Cancer develops when abnormal cells in your body grow uncontrollably and spread, which can form tumors and invade healthy tissue. Anyone can get cancer, but certain risk factors like smoking, sun exposure, and unhealthy diet increase your chances. Managing risk factors and staying on top of routine screenings can help you catch cancer early, when it's most treatable.