Digestive symptoms are common, which is why they can be easy to overlook.
However, a new and persistent change in bowel function should not automatically be attributed to age, diet, or stress.
The American Cancer Society identifies changes in bowel habits, rectal bleeding, abdominal pain, fatigue, and unexplained weight loss as possible symptoms of colorectal cancer. The CDC also emphasizes that colorectal cancer and precancerous polyps may exist without noticeable symptoms.
One particularly important lesson is that people should not wait until abdominal pain becomes severe before seeking help.
Early evaluation can identify many treatable digestive conditions and help determine whether more specialized investigation is necessary.
Chapter 4: Breathing Problems, Bleeding, and Other Unusual Symptoms
Not every possible warning sign of cancer involves the digestive system or a visible lump.
Some symptoms affect breathing, the urinary system, blood circulation, or the nervous system.
Because these symptoms can be associated with many different conditions, understanding their possible causes is important.
The following eight warning signs complete the list of 20.
13. Unexplained changes in urination
Changes in bladder habits are common as people get older.
Urinary infections, prostate enlargement, diabetes, kidney stones, and certain medications can all affect how frequently someone urinates.
However, persistent or unusual changes should be evaluated.
Potential warning signs include:
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Needing to urinate much more frequently.
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Difficulty starting urination.
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A weak or interrupted urine stream.
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Pain or burning during urination.
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Blood appearing in the urine.
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Feeling that the bladder does not empty completely.
Bladder cancer may cause blood in the urine, sometimes without pain.
Kidney cancer can also cause blood in the urine, although it may produce other symptoms or remain unnoticed initially.
In men, prostate enlargement and prostate cancer can sometimes produce overlapping urinary symptoms.
These symptoms are not enough to identify the underlying condition.
A medical assessment may involve urine testing, blood tests, imaging, or specialist examination.
Visible blood in the urine should be checked promptly, even if it occurs only once.
14. A persistent cough
Coughing is one of the body's natural ways of clearing irritants and mucus from the respiratory system.
Most coughs are caused by infections, allergies, asthma, acid reflux, or environmental irritation.
However, a cough that continues without a clear explanation deserves attention.
Some lung cancers can cause a persistent cough or a noticeable change in an existing cough.
People may find that they cough more frequently, experience repeated chest discomfort, or produce unusual mucus.
A cough that contains blood is particularly concerning and requires prompt medical evaluation.
Other symptoms may include unexplained weight loss, breathlessness, chest pain, and repeated respiratory infections.
People who smoke or have a history of significant exposure to harmful airborne substances may have additional risk factors.
Nevertheless, lung cancer can also occur in people who have never smoked.
A persistent cough should therefore be assessed based on the individual's overall health rather than smoking history alone.
15. Persistent hoarseness or voice changes
A person's voice may become temporarily hoarse because of a cold, throat infection, allergies, or excessive talking.
In most cases, the voice gradually returns to normal.
However, hoarseness that persists or repeatedly returns without an obvious explanation should be investigated.
Some cancers involving the larynx or nearby structures can affect the vocal cords and change the sound of the voice.
A person may notice:
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A rough or breathy voice.
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Difficulty speaking loudly.
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A persistent change in vocal quality.
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Discomfort when speaking.
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A feeling of irritation in the throat.
Other causes include vocal cord nodules, reflux, chronic inflammation, and neurological conditions.
A healthcare professional may examine the throat and recommend an ear, nose, and throat specialist if necessary.
16. Unexplained shortness of breath
Feeling breathless after intense exercise is normal.
However, becoming unusually short of breath during ordinary activities may indicate an underlying health problem.
A person might notice difficulty climbing stairs, walking a short distance, or performing everyday household tasks.
Possible causes include heart disease, asthma, anemia, blood clots, lung infections, and other respiratory conditions.
Lung cancer can also cause breathlessness, particularly when a tumor affects the airways, lung tissue, or surrounding structures.
Some people experience breathlessness alongside a persistent cough, chest discomfort, or unexplained fatigue.
Sudden or severe difficulty breathing is a medical emergency and should not be treated as an ordinary cancer warning sign. Emergency services should be contacted immediately.
17. Unusual bleeding or discharge
Unexplained bleeding can occur in several parts of the body.
Examples include:
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Bleeding between menstrual periods.
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Bleeding after menopause.
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Unusual vaginal discharge.
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Blood in the urine.
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Blood in the stool.
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Blood in coughed-up mucus.
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Unexplained nipple discharge.
Some forms of cancer involving the reproductive organs, urinary tract, digestive system, or lungs may produce abnormal bleeding.
For example, bleeding after menopause should always be medically assessed.
Although many cases are caused by benign conditions, endometrial cancer is one possible cause.
Similarly, unusual bleeding from the digestive tract can sometimes be associated with colorectal or stomach cancer.
The location, amount, frequency, and timing of bleeding all help guide the medical investigation.
18. Unusual bruising or bleeding that is difficult to explain
Bruises often develop after minor injuries that people do not remember.
Certain medications, including blood thinners, can also increase bruising.
However, frequent unexplained bruising, prolonged bleeding, or repeated nosebleeds may sometimes indicate a blood disorder.
Certain blood cancers, including leukemia, can interfere with the normal production of healthy blood cells.
This may affect platelets, which help the blood clot.
A person may notice bruises appearing without an obvious injury, small red or purple spots under the skin, or bleeding that takes longer than expected to stop.
Other possible symptoms include frequent infections, fever, and persistent fatigue.
A blood test can help doctors investigate abnormalities in blood cell counts.
19. Persistent or unexplained pain
Pain is an important signal that something may be wrong.
It can result from injuries, inflammation, infections, arthritis, nerve problems, and many other conditions.
However, new pain that does not improve or gradually becomes worse deserves attention.
Certain cancers can cause pain by pressing on nearby organs, bones, nerves, or other tissues.
For example, bone cancer may cause localized bone pain, while tumors in other areas may produce discomfort in the back, abdomen, or chest.
Pain is not always present during the early stages of cancer.
In addition, the absence of pain does not mean that a person is free from disease.
People should pay particular attention to persistent pain that has no clear explanation or is accompanied by other unusual symptoms.
20. Persistent headaches, vision changes, or neurological symptoms
The nervous system controls movement, sensation, balance, speech, and many other important functions.
Changes in neurological function can have numerous causes, including migraines, infections, medication effects, vascular conditions, and neurological disorders.
In some cases, tumors involving the brain or nervous system may produce symptoms such as:
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Persistent or progressively worsening headaches.
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New seizures.
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Unexplained vision changes.
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Hearing changes.
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Balance problems.
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Weakness or numbness.
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Difficulty speaking.
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Changes in behavior or concentration.
These symptoms should be evaluated based on their severity and progression.
A sudden severe headache, new seizure, facial drooping, or sudden weakness on one side of the body requires emergency assessment because it may indicate a stroke or another serious neurological emergency.
It is important not to assume that neurological symptoms automatically mean a brain tumor.