If you mean “20 early warning signs that may sometimes occur when cancer is developing,” it’s important to clarify one thing: there is no reliable list of symptoms that proves your body is “fighting cancer.” Many of these symptoms are much more commonly caused by infections, inflammation, medications, hormonal changes, digestive problems, or other non-cancerous conditions. The National Cancer Institute recommends getting persistent or worsening symptoms evaluated rather than trying to diagnose cancer from symptoms alone.
20 Possible Early Warning Signs of Cancer
1. Unexplained weight loss
Losing weight without changing your diet or exercise can sometimes be an early sign, particularly when the loss is substantial or continues over time. Cancer can affect appetite and the way the body uses energy. The American Cancer Society lists unexplained loss or gain of about 10 pounds or more as a symptom worth discussing with a healthcare professional.
Pay attention to: persistent weight loss accompanied by reduced appetite, weakness, abdominal symptoms, or other unexplained changes.
2. Persistent or unusual fatigue
Cancer-related fatigue can be different from ordinary tiredness. You may feel exhausted even after adequate sleep or relatively little physical activity. Cancer can contribute to fatigue through anemia, inflammation, nutritional problems, or changes in the body’s metabolism.
However, fatigue is extremely common and is more often caused by things such as poor sleep, anemia, infections, stress, thyroid problems, or other medical conditions.
3. A new lump or swelling
A new lump under the skin, in the breast, neck, armpit, abdomen, or groin deserves attention, especially if it persists or grows.
Swollen lymph nodes are often caused by infections or inflammation rather than cancer, but persistent, firm, or unexplained swelling should be examined.
4. Unexplained bleeding or bruising
Unexpected bleeding can occur with several different conditions, but unexplained bleeding is one of the symptoms doctors take seriously.
Examples include:
- Blood in the stool
- Blood in the urine
- Coughing up blood
- Unusual vaginal bleeding
- Frequent unexplained nosebleeds
- Bruising unusually easily
The significance depends greatly on your age, sex, medications, and other symptoms.
5. Changes in bowel habits
A persistent change in your normal bowel pattern can include:
- New constipation
- Persistent diarrhea
- Alternating constipation and diarrhea
- Narrower-than-usual stools
- A persistent change in stool appearance
- Feeling that you haven’t completely emptied your bowel
These changes have many possible causes, including diet, medications, irritable bowel syndrome, and infections. Persistent changes should nevertheless be evaluated.
6. Blood in the stool
Blood in the stool can appear bright red, dark, or sometimes be hidden and detectable only through testing.
Hemorrhoids and other non-cancerous conditions are common causes, but colorectal cancers can also cause bleeding. Therefore, unexplained or recurrent blood in the stool shouldn’t simply be assumed to be hemorrhoids.
7. Persistent cough or hoarseness
A cough that doesn’t resolve, particularly when it is new or progressively worsening, should be assessed.
Persistent hoarseness can also be important. These symptoms may result from infections, allergies, asthma, reflux, smoking, or other conditions—not necessarily cancer.
8. Shortness of breath
New or unexplained breathlessness can have many causes, including asthma, heart problems, anemia, infections, and lung disease.
Because some cancers can affect the lungs or surrounding structures, persistent unexplained shortness of breath should be medically evaluated rather than self-diagnosed.
Seek urgent medical care for severe or sudden difficulty breathing, especially with chest pain, fainting, blue lips, or confusion.
9. Persistent or unexplained pain
Cancer can sometimes cause pain when a tumor presses on nearby organs, tissues, nerves, or bones. Pain may be localized or more widespread depending on the underlying condition.
But pain is extremely nonspecific. Back pain, headaches, abdominal pain, joint pain, and muscle pain are much more commonly caused by non-cancerous conditions.
The important features are new, persistent, unexplained, progressively worsening, or otherwise unusual pain.
10. Persistent fever
An unexplained fever that repeatedly occurs or doesn’t resolve can sometimes accompany cancer, particularly certain blood cancers.
But infections are overwhelmingly more common causes of fever. Fever associated with other symptoms—such as unexplained weight loss, night sweats, persistent fatigue, or enlarged lymph nodes—deserves medical assessment.
11. Drenching night sweats
Occasional sweating at night is usually not concerning. More significant are repeated, unexplained, drenching night sweats that soak your clothing or bedding.
Night sweats can occur with infections, hormonal changes, medications, anxiety, and many other conditions, as well as some cancers.
12. Changes in a mole or other skin lesion
Watch for:
- A new mole appearing
- A mole becoming asymmetrical
- Irregular borders
- Multiple or changing colors
- Increasing size
- A mole that changes over time
- A sore that doesn’t heal
- A skin growth that repeatedly bleeds or becomes scaly
These changes don’t automatically mean skin cancer, but changing lesions should be examined.
13. A sore that doesn’t heal
A persistent sore on the skin or in the mouth that doesn’t heal normally deserves attention.
Particularly concerning changes include a sore that:
- Continues for weeks
- Bleeds repeatedly
- Becomes increasingly painful
- Develops a lump
- Changes in appearance
Persistent mouth sores or patches should also be evaluated by a healthcare professional or dentist.
14. Persistent difficulty swallowing
Trouble swallowing—called dysphagia—can involve difficulty swallowing solid foods, liquids, or both.
Possible causes include reflux, inflammation, neurological conditions, narrowing of the esophagus, and other problems. Certain cancers can also cause swallowing difficulties.
Progressive difficulty swallowing or unexplained weight loss alongside swallowing problems warrants prompt medical evaluation.
15. Persistent indigestion, bloating, or abdominal discomfort
Ongoing:
- Indigestion
- Heartburn
- Abdominal discomfort
- Bloating
- Feeling unusually full after eating
- Nausea
- Loss of appetite
can sometimes occur with cancers of the digestive system. For example, the NCI notes that some people with early stomach cancer may experience indigestion, bloating after eating, mild nausea, appetite loss, or heartburn.
However, these symptoms are far more commonly caused by ordinary gastrointestinal conditions.
16. Persistent changes in urination
Possible warning signs include:
- Blood in the urine
- Burning or pain when urinating
- Needing to urinate much more frequently
- A persistent urge to urinate
- Difficulty urinating
- Significant changes in normal urinary patterns
Blood in the urine is particularly important to have checked. Although bladder cancer can cause it, urinary infections, kidney stones, prostate problems, and other conditions can also cause it.
17. Unexplained loss of appetite
A sustained reduction in appetite without an obvious explanation can accompany some cancers.
It becomes more important when combined with:
- Unintentional weight loss
- Persistent nausea
- Abdominal discomfort
- Difficulty swallowing
- Severe fatigue
Loss of appetite itself is nonspecific and can result from medications, infections, depression, gastrointestinal disorders, and many other conditions.
18. Persistent mouth changes
Changes that should be checked include:
- A sore that doesn’t heal
- A white patch
- A red patch
- Unexplained bleeding
- Persistent mouth pain
- Numbness
- Difficulty chewing or swallowing
- A lump in the mouth or neck
These symptoms can have many causes, but persistent mouth changes should be evaluated by a dentist or healthcare professional.
19. Jaundice or yellowing of the skin/eyes
Yellowing of the whites of the eyes or skin is called jaundice.
It can occur when bilirubin builds up in the body. Causes include gallstones, hepatitis, liver disease, medication effects, and problems affecting the bile ducts or pancreas. Some cancers can also cause jaundice.
New unexplained jaundice should be medically evaluated promptly.
20. Persistent headaches, vision, hearing, or neurological changes
Some cancers affecting the brain or nervous system can produce neurological symptoms such as:
- Persistent or unusual headaches
- Seizures
- Vision changes
- Hearing changes
- Weakness
- Facial drooping
- Problems with coordination
Most headaches and many neurological symptoms are not caused by cancer. But a new, severe, persistent, or progressively worsening neurological symptom requires medical attention.
The most important point
Having one or even several of these symptoms does NOT mean you have cancer. In fact, the NCI specifically notes that cancer symptoms are often caused by illness, injury, benign tumors, or other problems.
What matters more is a symptom that is:
- New
- Unexplained
- Persistent for several weeks
- Getting worse
- Associated with unexplained weight loss or bleeding
- Significantly different from your normal health
If something like this is happening, it’s better to have a clinician investigate the cause rather than waiting for more symptoms. Cancer also doesn’t always cause symptoms early, which is why recommended screening can be important even when you feel completely healthy.
If you tell me your age, sex, and the specific symptoms you’re experiencing (including how long you’ve had them), I can explain what they may mean and which ones warrant prompt medical evaluation.