Symptoms of Cancer: What to Watch For
A plain-language overview of common symptoms that cancer may cause and when to see a doctor, based on National Cancer Institute resources.
Source: National Cancer Institute · NCI reviewed 2019-05-16 · Verified 2026-07-02
5 min readBeginnerUpdated 2026-07-02
The 30-second version
Cancer can cause many symptoms, but these symptoms are most often caused by other problems, such as illness, injury, or benign tumors. If you have symptoms that do not get better after a few weeks, see a doctor so problems can be found and treated early. Cancer often does not cause pain.
Key takeaways
- Cancer can cause many symptoms, but these are most often caused by illness, injury, benign tumors, or other problems.
- If symptoms do not get better after a few weeks, see a doctor so problems can be diagnosed and treated early.
- Cancer often does not cause pain, so do not wait to feel pain before seeing a doctor.
- Symptoms can affect many parts of the body, including the breast, bladder, bowel, skin, and mouth.
- Unexplained bleeding, bruising, fatigue, fever, or weight change can be among the symptoms cancer may cause.
- Each specific type of cancer has its own detailed symptom information.
Choose how you want to understand this
The full explanation.
The simple version
Cancer can cause many symptoms, but these symptoms are most often caused by illness, injury, benign tumors, or other problems.
If you have symptoms that do not get better after a few weeks, see your doctor so that problems can be diagnosed and treated as early as possible. Often, cancer does not cause pain, so do not wait to feel pain before seeing a doctor.
Most symptoms are not cancer — but symptoms that stick around for a few weeks are worth checking with a doctor.
Don't wait for pain
One of the most important points is that cancer often does not cause pain. It can be tempting to wait until something hurts before seeing a doctor. But if you have symptoms that last for a couple of weeks, it is important to see a doctor rather than waiting for pain to appear.
Seeing a doctor early gives the best chance for any problem—whether it is cancer or something else—to be found and treated as early as possible.
Symptoms cancer may cause
Some of the symptoms that cancer may cause include the following. Remember that these are most often caused by conditions other than cancer.
Breast changes
- Lump or firm feeling in your breast or under your arm
- Nipple changes or discharge
- Skin that is itchy, red, scaly, dimpled, or puckered
Bladder changes
- Trouble urinating
- Pain when urinating
- Blood in the urine
Bleeding or bruising, for no known reason
Bowel changes
- Blood in the stools
- Changes in bowel habits
Cough or hoarseness that does not go away
Eating problems
- Pain after eating (heartburn or indigestion that doesn't go away)
- Trouble swallowing
- Belly pain
- Nausea and vomiting
- Appetite changes
Fatigue that is severe and lasts
Fever or night sweats for no known reason
Mouth changes
- A white or red patch on the tongue or in your mouth
- Bleeding, pain, or numbness in the lip or mouth
Neurological problems
- Headaches
- Seizures
- Vision changes
- Hearing changes
- Drooping of the face
Skin changes
- A flesh-colored lump that bleeds or turns scaly
- A new mole or a change in an existing mole
- A sore that does not heal
- Jaundice (yellowing of the skin and whites of the eyes)
Swelling or lumps anywhere, such as in the neck, underarm, stomach, and groin
Weight gain or weight loss for no known reason
Learning about a specific cancer
The list above covers general symptoms. Each type of cancer can have its own symptoms. To learn about symptoms for a specific cancer, the National Cancer Institute provides PDQ cancer treatment summaries for adult and childhood cancers, and each summary includes detailed information about symptoms caused by that specific type of cancer.
The best next step for any symptom that lasts is to see a doctor — early answers help, whatever the cause.
Watch instead
Animated lessons are in production. Here’s the planned video slate for this topic — each one will be based on the same NCI-sourced explanation you’re reading.
Symptoms of Cancer: What to Watch For: the quick overview
A one-breath explanation you can watch before an appointment.
Coming soonSymptoms of Cancer: What to Watch For, explained simply
The core ideas with friendly animation and plain language.
Coming soonUnderstanding symptoms of cancer: what to watch for — full lesson
A deeper walkthrough covering the key takeaways and common questions.
Coming soonVideo transcript▾
A full, readable transcript will appear here when the video is published — so the lesson is accessible whether you prefer to watch, listen, or read. For now, the article above is the complete text version.
Suggested animation storyboard▾
- 1Open on a calm title card: "Symptoms of Cancer: What to Watch For" with the Cancer Explained mark.
- 2Narrator reads the 30-second summary while a soft animated diagram builds on screen: "Cancer can cause many symptoms, but these symptoms are most often caused by other problems, such as illness, injury, or benign tumors. If you have symptoms that do not get better after a few weeks, see a doctor so problems can be found and treated early. Cancer often does not cause pain."
- 3Scene 2: illustrate the idea — "Cancer can cause many symptoms, but these are most often caused by illness, injury, benign tumors, or other problems."
- 4Scene 3: illustrate the idea — "If symptoms do not get better after a few weeks, see a doctor so problems can be diagnosed and treated early."
- 5Scene 4: illustrate the idea — "Cancer often does not cause pain, so do not wait to feel pain before seeing a doctor."
- 6Close on a reminder card: this is educational only; talk with your healthcare team, and a link to the NCI source.
Words to know
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Quick knowledge check
According to this article, what most often causes the symptoms that cancer can cause?
Frequently asked questions
▸What are common symptoms of cancer?
Cancer may cause many symptoms. Some examples include breast changes such as a lump, bladder changes such as trouble or pain when urinating, unexplained bleeding or bruising, bowel changes, a lasting cough or hoarseness, eating problems, severe and lasting fatigue, fever or night sweats for no known reason, mouth changes, neurological problems, skin changes, swelling or lumps, and unexplained weight gain or loss.
▸Do these symptoms mean I have cancer?
Not usually. Cancer can cause many symptoms, but these symptoms are most often caused by illness, injury, benign tumors, or other problems. Still, if you have symptoms that do not get better after a few weeks, it is important to see a doctor so problems can be diagnosed and treated as early as possible.
▸When should I see a doctor about symptoms?
See your doctor if you have symptoms that do not get better after a few weeks. Cancer often does not cause pain, so do not wait to feel pain before seeing a doctor. Seeing a doctor early helps problems get diagnosed and treated as early as possible.
▸Does cancer always cause pain?
No. Often, cancer does not cause pain. That is why the National Cancer Institute advises not to wait to feel pain before seeing a doctor. If you have symptoms that last for a couple of weeks, it is important to see a doctor.
▸What skin changes can be a symptom of cancer?
Skin changes that cancer may cause include a flesh-colored lump that bleeds or turns scaly, a new mole or a change in an existing mole, a sore that does not heal, and jaundice (yellowing of the skin and whites of the eyes). A doctor can evaluate any of these changes.
▸Where can I find symptoms for a specific type of cancer?
To learn about symptoms for a specific cancer, the National Cancer Institute provides PDQ cancer treatment summaries for adult and childhood cancers. Each summary includes detailed information about symptoms caused by that specific type of cancer.
Test your understanding
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Review key terms
Study 10 flashcards built from this topic’s key terms and common questions — flip each card to reveal a plain-language explanation.
Questions to ask your healthcare team
Consider bringing these questions to your next appointment.
- I have had this symptom for a few weeks—could it be something serious?
- What tests can help find the cause of my symptom?
- Should I be watching for any other symptoms?
- Which symptoms should prompt me to call you right away?
- Could my symptom be caused by something other than cancer?
- How soon should I be seen if a symptom does not improve?
- Where can I read about symptoms for a specific type of cancer?
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