By Maxine Lipner 

Published on July 27, 2023

 Medically reviewed by Doru Paul, MD

With cancer, abnormal cells grow out of control. These cells were damaged and don't go through the typical steps of dividing in an orderly manner. Instead, they may multiply out of control and sometimes clump together, forming tumors.

Abnormal cancerous cells can spread (metastasize) elsewhere in the body, where they can develop into new tumors. While you can feel many cancerous tumors that form masses, you can't detect all cancers by touch. Cancer of the blood, for example, is not solid. Also, not all solid masses are cancerous. Some tumors are benign (noncancerous) and do not spread or invade nearby tissue.¹

More than 200 different types of cancer have been identified. Each is classified by where it starts in the body (such as the brain, bone, blood, or skin) or the type of tissue or cells from which it develops.²

Here you'll learn what can cause cancer and what factors can put you at risk, how cancer progresses, the most common types, how symptoms vary by type, what tests are used for diagnosis, various tre atments, and more.

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Causes: How Do You Get Cancer?

The genes inside a cell control cell growth. They make proteins that instruct cells how to function. But if genes become altered (mutate), this process is put in jeopardy. Some of these changes may allow the cells to grow out of control.³

Genes are constantly being damaged. In many cases, cells can repair this damage. However, if there is too much damage, such repair may not be possible. The cells may begin to grow out of control. What's more, once these cells begin to grow fast, they're prone to picking up more mutations, and the chance of repair begins to wane.⁴

Risk factors are things that make it more likely that a mutation will occur. These can come from within the cell or from outside it. Here are some risk factors to be aware of:⁵

• Having a flawed gene inherited from a parent that puts you at greater risk of developing cancer

• Consuming alcohol

• Smoking tobacco

• Having a human papillomavirus (HPV) infection

• Being overweight

 Causes and Risk Factors of Cancer

How Cancer Cells Start and Spread

In some cases, such as if you have skin cancer, you may notice a sore that doesn't heal or that oozes, a shiny bump, or a pigmented lesion with uneven borders. By the time you see such signs, the cancer has likely been brewing for a while.⁶

How does this process get going? You have trillions of cells in your body, and cancer can start in any one of them. The difference between cancer cells and noncancerous cells is that normal, healthy cells only grow when they are instructed to, but cancerous ones ignore some signals, such as ones that tell them to stop growing or to die (apoptosis) if they are no longer healthy.

But if genes become damaged, cancerous cells don't follow the normal rules. While the immune system can sometimes get rid of the damaged genes, in some cases, the flawed cells are able to evade this, and the cancerous cells can grow and form tumors.

From there, a cancerous cell may break away and spread through the blood or the lymph system to other parts of the body. It may leave the vessels and settle into a new site, causing more tumors to grow. The process may then repeat itself.¹

Types of Cancer

While cancer can, unfortunately, strike any part of the body, some areas are more vulnerable than others. Nonmelanoma skin cancer (primarily basal cell carcinoma and squamous cell carcinoma) is the most common type of cancer.⁷ These cancers are less likely to invade other tissues or result in death.

The estimated number of other U.S. cancer diagnoses for 2023, from most diagnosed down, were:⁸

• Breast cancer

• Prostate cancer

• Lung cancer

• Colon and rectal cancers

• Melanoma

• Bladder cancer

• Kidney (renal cell and renal pelvis) cancer

• Non-Hodgkin lymphoma

• Endometrial cancer

• Pancreatic cancer

• Leukemia

• Thyroid cancer

• Liver cancer

In the United States, lung cancer is responsible for the highest number of deaths, followed by colon and rectal cancer, pancreatic cancer, breast cancer, and other tumors.⁹

Common Symptoms of Cancer

The symptoms you experience due to cancer will likely vary depending on where in the body it occurs. Common symptoms of cancer include the following:¹⁰

• Fatigue: If you find yourself continually dragging for no reason, see a healthcare provider. While fatigue may occur due to stress or other conditions, cancer can often produce this symptom.

• Mysterious bruising or bleeding: Finding a bruise is unsurprising if you know where it came from. But one that appears for no apparent reason could be serious. Vaginal bleeding outside of menstruation (including after menopause or after sex), anal bleeding or blood in the stool, or coughing up blood should be checked by a healthcare provider.

• Drenching night sweats: Unless you have a fever due to infection or are experiencing menopause, waking up to find your sheets sticking to you even though your room is temperate can be a concerning sign. You would be wise to check this out with a healthcare provider.

• Losing weight unexpectedly: Watching pounds drop off unexpectedly can be a troubling sign of cancer. Let a healthcare provider know if you're losing weight for no reason.

• Finding a lump: While there may be a simple explanation for an unusual lump or swelling for no reason, the lump could be caused by cancer and needs to be checked out.

• Feeling pain: It's not uncommon to complain of an ache or pain now and again, but if this occurs often and is not linked to an obvious cause, have it looked at promptly.

How Is Cancer Diagnosed?

Tests will be required to make a diagnosis. Here are some of the methods that may be needed:

• You may need lab tests such as blood work, blood counts, identifying cancer markers in the blood, and urinalysis as part of the process.

• Your oncologist (cancer specialist) may perform diagnostic imaging with the aid of computed tomography (CT) scans, X-rays, and fluoroscopy (akin to an X-ray video) to identify areas that may be cancerous. They may also do a lymphangiogram (to examine the lymph system) or a mammogram of breast tissue. With these kinds of scans, a beam of energy shows structures as it passes through the body.

• Other types of diagnostic imaging tests include ultrasound, in which sound waves bounce off different structures at different speeds to produce an image; emission imaging, which relies on detecting nuclear particles taken up by actively growing cells; and magnetic resonance imaging (MRI), which uses a strong magnetic field and radio waves.

• You may need an endoscopic exam in which a tiny camera attached to a long tube is placed inside the body to help view different areas.

• Genetic testing may be recommended to detect any genes that may have put you at increased risk for cancer.

• A biopsy of a tumor removes a sample tissue to be viewed under a microscope to determine if it is cancerous.¹¹

 How Cancer Is Diagnosed

Cancer Treatment

Depending on the type of cancer, your oncologist will design a treatment plan specifically for you, which may include one of the following or a combination of approaches.

Chemotherapy

With chemotherapy, drugs are used to kill cancer cells. The medication is transported by the bloodstream throughout the body. In addition to shrinking and killing tumors, chemotherapy can, unfortunately, damage some healthy cells as well.

Chemotherapy can be used as a first-line treatment to try to cure the cancer, or it may be used to shrink tumors before giving other treatments. It can also be used after treatments such as surgery or radiation to try to clean up any lingering cancer cells.¹²

Radiation Therapy

This approach uses high doses of radiation from X-rays, electron beams, or gamma rays that create tiny breaks in DNA and, in turn, work to shrink or destroy cancer cells. The radiation is aimed locally at the area affected by the cancer and does not travel throughout the body.

Radiation therapy is given to over half of those with cancer.¹³ It sometimes is the only treatment or it can be combined with other approaches, such as chemotherapy. It can be given on its own, to shrink tumors before surgery, or to mop up lingering cells after surgery.¹³

Surgery

Surgery is a staple of cancer treatment for many. It can be used on its own to treat cancer or with other approaches. Whether you will be a candidate for surgery depends on the type of cancer you have, where it is located, how large a tumor it is, and the general state of your health.

Surgery can only be used for solid tumors and not for something like leukemia, where cells are dispersed throughout the body. Likewise, if the cancer has metastasized (spread to distant areas of the body) already, surgery may not be the recommended approach. Instead, your oncologist will likely recommend a systemwide treatment.¹⁴

Targeted Therapy

Using targeted therapy, oncologists can lock in on cancer cells themselves by targeting proteins associated with cancer cell growth and how these cells divide.

With this precision approach, they may use monoclonal antibodies that attach to proteins on cancer cells, flagging these to make them more easily detected by the immune system, which can then destroy them. Or, these antibodies may be paired with toxins, which kill cancer once they are delivered to the site.

Other targeted approaches may include preventing blood vessels needed for tumor growth from attaching to a mass of cancer cells. Or, these treatments may interfere with signals that allow cancer cells to divide and grow.¹⁵

Immunotherapy

With immunotherapy, also known as biological therapy, the body's own immune system is used to fight cancer. The idea is to enhance the way the immune system works so that cancer cells can't evade it any longer.

There are several strategies that can be used, such as:¹⁶

• Immune checkpoint inhibitors: Usually, the immune system can be cut off from responding too vigorously at certain key checkpoints. But when you want a strong response, as in the case of cancer, the idea is to use drugs to put these checkpoints out of commission and allow the immune system to respond forcefully.

• Immune system modulators: With the use of these, the immune system can be either charged up or suppressed, depending on the effect needed.

• Monoclonal antibodies: These antibodies made in the lab are intended to latch onto cancer cells so the immune system can destroy them.

• Cancer vaccines: The idea with this approach is to train the immune system to detect cancer cells and then kill them.

Complementary and Alternative Medicine (CAM)

The idea of complementary and alternative medicine is to augment standard therapy. This can range from helping to ease stress to working to relieve treatment side effects. Approaches here can include the following:¹⁷

• Mind-body therapies such as meditation, biofeedback, hypnosis, or yoga

• Biological and nutritional supplements such as vitamins, minerals, and herbs

• Botanicals ranging from herbs and spices to cannabis

• The use of alternative medicine, such as a special diet

• Body-based practices such as massage, chiropractic therapy, or reflexology

• Energy healing based on the idea that energy runs on pathways through the body, including using techniques such as acupuncture, reiki, and therapeutic touch

Palliative Care

Palliative care is meant to improve the quality of life rather than cure a condition. It aims to lessen symptoms and side effects that may arise from the cancer itself or from a treatment. It may range from managing physical problems such as nausea and shortness of breath to emotional and spiritual ones.¹⁸

Cancer Staging

Determining what stage your cancer has progressed to is pivotal in fighting this condition. It helps your oncologist to determine the best treatment for you and whether you are eligible for upcoming clinical trials that are studying new approaches.

Your oncologist may describe your cancer in the following ways:¹⁹

• In situ: Cancer cells have been found at the original site but not in nearby tissue.

• Localized: This means that the cancer remains strictly at the site where it was found, with no signs of spreading elsewhere.

• Regional: The cancer has spread to nearby lymph nodes, organs, or tissues.

• Distant: The cancer is no longer just in the area where it began. It has spread to distant areas of the body.

They may also use more specific staging terminology. The "TNM" system stands for "tumor," "node," and "metastasis," as follows:

• T is the size of the tumor, with a number ranging from 1 to 4 that denotes small to large size.

• N denotes whether the cancer has spread to the lymph nodes, with numbers ranging from 0, meaning no lymph node involvement, to 3, suggesting many lymph nodes have been affected.

• M denotes that the cancer has metastasized elsewhere in the body. Zero (0) means the cancer hasn't spread, and a 1 indicates that it has.

Staging ranges from 1 to 4 and general includes the following information:²⁰

• Stage 1 indicates that the cancer is small and still contained within the organ where it was initially detected.

• Stage 2 indicates that while it is bigger than a stage 1 tumor, the cancer still has not spread to the lymph nodes. In stage 2 of some types of cancer, such as lung or breast cancer, it may have spread to the lymph nodes also.

• Stage 3 indicates that the tumor has increased in size and cancer has been found in nearby lymph nodes.

• Stage 4 indicates that the tumor has now spread from the original site to another organ.

As staging definitions may be different for the type of cancer you have, your oncologist can explain in detail what the stage of cancer means for your treatment plan and prognosis.

Can You Prevent Cancer?

Cancer can occur in any person, even when you have tried to eliminate risk factors that are under your control.

Healthy life choices may lower the risk of developing some types of cancer. These include healthy eating, avoiding smoking, wearing sunscreen, keeping alcohol consumption to a minimum, and taking other protective steps, such as HPV vaccination.²¹

Detecting cancer early with the aid of regular screening tests for breast cancer, cervical cancer, colorectal cancer, lung cancer, and prostate cancer can improve treatment outcomes.²² See a healthcare provider regularly to ensure you get appropriate screenings and have any early symptoms of cancer addressed.

How to Find an Oncologist

To find the right cancer specialist, you may start by talking to your primary care healthcare provider and asking for suggestions.

Another possibility is to search the American Society for Clinical Oncology database. The Centers for Medicare and Medicaid Services provides a search tool for an oncologist who takes Medicare.²³

Outlook

No two cases of cancer are necessarily alike. Some types of cancer have a favorable outlook, especially when caught at an early stage.

The outlook in your particular case will depend on the type of cancer you have been diagnosed with its stage, and the type of treatment available. Other factors that influence prognosis include the following:²⁴

• How aggressive the cancer is

• Your health before being diagnosed with cancer

• How well you respond to treatment

If you are looking for support, the American Cancer Society has a helpline (800-227-2345) and online chat to connect to an information specialist who can help answer your questions.

Other support services you can search for on the American Cancer Society website include:²⁵

• Rides to treatment

• Grants for lodging when traveling for treatment

• A peer support network

• A resource list to help patients navigate support options

Finding a Caretaker

People seeking a caregiver can contact a home healthcare agency that will provide a screened and supervised caregiver. To find such an agency near you, use this home health agency locator. While it is a Medicare-related service, you do not have to be a part of the program to use this locater.²⁶

Summary

Cancer starts on the cellular level, with genetic changes allowing a cancerous cell to multiply out of control. Symptoms arise as cancer growth begins to affect the tissues and organs in which it starts. It may eventually spread elsewhere in the body.

The symptoms you experience will be unique to you and the type of cancer you have. Likewise, your oncologist will design a treatment plan just for you. How you fare will depend on the specifics of your cancer, how aggressive it is, the available treatment options, and your unique makeup.