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Warning Signs of Cancer


Robert Peter Gale

, MD, PhD, Imperial College London

Last full review/revision Sep 2020| Content last modified Sep 2020
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Cancer can cause many different symptoms, some subtle and some not at all subtle. (See also Overview of Cancer and Symptoms of Cancer.)

Some symptoms develop early in the course of cancer, such as a painless lump in the breast, and are therefore important warning signs that should be evaluated by a doctor. Other symptoms, such as weight loss or fever, develop only after the cancer progresses. Still other symptoms, such as a change in bowel habits, blood in the stool, or swallowing difficulty, are signs of cancer in specific sites of the body.

Because cancer is more likely to be cured if it is less advanced when treatment is begun, it is critical that cancer be discovered early. Some symptoms may give early warning of cancer and should, therefore, trigger a person to seek medical care. Fortunately, most of these symptoms are usually caused by far less serious conditions. Nonetheless, the development of any of the warning signs of cancer should not be ignored.

Some of the warning signs are general. That is, they are vague changes that do not help pinpoint any particular cancer. Still, their presence can help direct doctors to do the physical examinations and laboratory tests necessary to exclude or confirm a diagnosis. Other symptoms are much more specific and steer doctors to a particular kind of cancer or location.

Warning signs of possible cancer include the following:

  • Unexplained weight loss

  • Fatigue

  • Night sweats

  • Loss of appetite

  • New, persistent pain

  • Recurrent nausea or vomiting

  • Blood in urine

  • Blood in stool (either visible or detectable by special tests)

  • A recent change in bowel habits (constipation or diarrhea)

  • Recurrent fever

  • Chronic cough

  • Changes in the size or color of a mole or changes in a skin ulcer that does not heal

  • Enlarged lymph nodes

  • A sore that does not heal

  • A growth or mark on the skin that gets larger or changes in appearance

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