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What is Cancer

Cancer can take on many forms and affect patients in a lot of different ways. It can be a difficult thing to understand for patients and family. We've compiled this cancer information to help you get a better understanding of what cancer is, how it develops, and how it can be treated. Arming yourself with the proper cancer information can help you understand, prepare for, and cope with cancer.

Cancer Information: What Is Cancer?

Put simply, cancer is the abnormal growth of cells. Cancers arise from an organ or body structure and are composed of tiny cells that have lost the ability to stop growing. This growing structure then sticks out from that organ or body structure until it reaches a size large enough to be noticed by a patient or physician. Occasionally, cancer may be detected "incidentally" by a laboratory test or X-ray - that is, the test or X-ray may have been ordered for purposes of routine screening or for an entirely different reason; in such a case, the cancer gets noticed almost by accident. At this point, it may be referred to as a "mass," a "growth," a "tumor," a "nodule," a "spot," a "lump," a "lesion," or a "malignancy."

In general, the cancer must reach a size of one centimeter (that is, between one-third and one-half of an inch), or be comprised of one million cells, before it is detected. Exceptions to this general rule include cancers of the blood and bone marrow - called lymphomas and leukemias - which frequently do not produce a "mass," but will be evident on laboratory tests; these cancers still require more than a million cells to be present before they are detected. Lymphomas and leukemias are examples of "liquid tumors" - or cancers present in body fluids (the blood and bone marrow), and are detectable by blood laboratory tests. "Solid tumors," including cancers of the lung, breast, prostate, colon and rectum, bladder, are not present in large enough numbers in body fluids to be detected with a blood test. However, they may release chemicals that are detectable in body fluids. (A person with prostate cancer, for example, may have an elevated level of Prostate-specific Antigen, or PSA, in the blood stream).

Cancer Information: Where In the Body Can Cancer Develop?

Cancer can occur anywhere in the body. Any area of the body that you can name can be the target area for a cancer. Some cancers even arise in parts of the body that only contained structures when that person was just an embryo -- only weeks after conception! Cancer cells - those abnormal cells that have lost the ability to stop growing - arise from cells that used to be normal components of organs and tissues. What causes cells to become cancerous? Cells grow abnormally because of environmental factors (such as cigarette smoking or radiation exposure), dumb luck, and as yet unexplained causes. And "just dumb luck" explains the majority of cancers.

Cancer Information: What Makes Cancerous Cells Stop Growing?

Cancer cells continue to grow unless one of four things occurs: 1) The cancerous mass is removed by a surgeon; 2) Chemotherapy or another type of cancer-specific medication, such as hormonal therapy, is given to the person with cancer; 3) A person with cancer receives radiation therapy; or 4) The cancer cells shrink and disappear on their own. This last event, while extremely rare, can occur with some melanomas (a type of skin cancer) or some kidney cancers.

Why Not Just Let the Cancer Grow?

In some cases, this may be the right thing to do. Since some cancers grow very slowly, exposing a person with a slowly growing tumor to either surgery or chemotherapy may make him/her very sick without doing much to improve that person's survival. Older adults in particular are more prone to experience the side effects of therapy; if those side effects outweigh the potential benefit of therapy or the potential harm of living with cancer, then the proposed therapy may not really be of benefit. This is where the notion of "quality of life" becomes important. Alternatively, a person may be ideologically opposed to therapy; for that individual, letting the cancer grow might be the right thing to do.

In other cases, letting the cancer grow may not be the right thing to do. Unfortunately, many cancer cells do not respect the boundaries of other organs or body structures. A growing cancer might either press on another organ and prevent that organ's ability to function normally, or it might actually invade another organ, and prevent that organ's ability to function normally. At these times, a situation may be created in which bleeding or an infection might occur. A lung cancer, for example, might press on the esophagus (the tube that carries food from the mouth to the stomach) and block the transit of food. A person with this cancer might describe a sensation of "…food getting caught in my throat - I just can't get it down." Alternatively, if the cancer invaded a blood vessel in the lungs, bleeding would occur, and a person might describe episodes of "coughing up blood."

Cancer Information: Why Does Having Cancer Make a Person Feel Sick?

Some types of cancer release chemicals that make a person feel ill. These chemicals, called "cytokines," may cause fevers, chills, sweats, fatigue, anorexia (the loss of appetite), or even nausea and vomiting. These are the same chemicals released into the bloodstream when a person has the flu; this explains why the symptoms of flu and of cancer often are similar. One of these cytokines, called "tumor necrosis factor" or "TNF," used to be called "cachexin" because its release from cancer cells was associated with cachexia, or wasting. These symptoms are, in fact, the ones that often bring a person with cancer to a doctor's attention in the first place. As a cancer continues to grow, these chemicals continue to be released. Treating the cancer should alleviate these symptoms.

Is Cancer Curable?

The short answer to this question is "Yes." In fact, all cancers are curable if they are caught early enough. That is the justification for screening tests, (such as mammograms, colonoscopies, and prostate exams). When cancers are caught early, they tend to be smaller; they are thus either easier to remove surgically, or more likely to shrink in response to chemotherapy or radiation therapy.

Cancers not caught "early enough" (when they are no longer small in size or few in number) may be curable, and almost certainly are treatable. Even advanced cancers that have spread to different parts of the body are usually treatable. More often, they are thought of as "chronic diseases," meaning they are diseases a person will live with over a long period of time. While a given therapy may not be able to cure the disease, it may be able to extend a person's life until a more promising, and potentially curative, therapy becomes available.

Where Can I Get More Cancer Information?

This website is a remarkable resource. The Taussig homepage provides a gateway to a lot of useful cancer information. Also, our cancer information and answer line is available by calling 1.866.223.8100 Monday through Friday from 8:00 A.M to 4:30 P.M.

Cancer Answers & Appointments

Speak with a cancer nurse specialist for appointment assistance and for answers to your questions about cancer locally at 216.444.7923 or toll-free 1.866.223.8100.

Monday through Friday from 8 a.m. – 4:30 p.m. (ET).

Referrals

Resources for medical professionals

  • Outpatient appointment referrals: 216.444.7923 or 866.223.8100
  • Inpatient hospital transfers: 800.553.5056
  • Referring Physician Concierge: 216.444.6196 or 216.312.4910.

Clinical Trials

Search available cancer clinical trials by disease, hospital, phase or number.

This information is provided by Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.

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