The short answer
Possible breast cancer signs include a new lump, changes in breast size or shape, skin dimpling, nipple changes, or discharge. Many of these have non-cancer causes, but any new or lasting change should be checked by a doctor.
A new lump in the breast or underarm is the most common sign, but not all lumps are cancer.
Other signs include changes in breast size or shape, skin dimpling, or redness.
Nipple changes, such as turning inward or new discharge, can also be signs.
Many breast changes have non-cancer causes, but new or lasting ones should be checked.
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The full explanation.
The simple version
Breast cancer can cause a lump or other changes in the breast. But many breast changes are not cancer. Knowing the possible signs helps you notice changes and get them checked. Screening can also find breast cancer before any symptoms appear.
The most common sign: a new lump
The most common sign of breast cancer is a new lump or mass. It can be in the breast or under the arm. A lump linked to cancer is often painless. It can feel hard, with edges that are not smooth. But lumps can also feel soft, tender, or round. Because of this, any new lump should be checked. You cannot tell by touch alone whether it is cancer.
Other changes to watch for
Breast cancer can also cause changes that are not a lump:
- Swelling, or a change in the size or shape of a breast
- Skin that dimples or puckers, sometimes described as looking like an orange peel
- Redness, scaling, or thickening of the skin on the breast, nipple, or areola
- A nipple that turns inward, or fluid coming from the nipple that is not breast milk
- A rash on the breast skin that does not clear up
Pain is usually not the main clue
Breast cancer does not usually cause pain, especially early on. Pain is more often linked to non-cancer causes, such as hormonal changes or cysts. This matters because it is easy to assume that "no pain" means "no problem." A painless lump deserves the same attention as a painful one.
Symptoms of cancer that has spread
If breast cancer spreads beyond the breast, it can cause other symptoms. These depend on where it spreads. They can include back pain, bone pain, or a bone that breaks more easily than expected. Shortness of breath can also occur. These symptoms have many other causes too. But if you have a breast cancer history and notice new symptoms like these, tell your doctor.
Many breast changes are not cancer
Many breast changes come from non-cancer causes, such as cysts, normal hormonal shifts, or infection. This is genuinely reassuring — most lumps and changes turn out to be benign. But because some changes are signs of cancer, any new or lasting change should still be evaluated by a doctor. Waiting to see if it goes away on its own is not the safer choice.
Follow up with your doctor when you notice a breast change, even if you had a recent normal mammogram. A mammogram is a picture taken at one point in time. It cannot rule out a change that shows up later.
Screening finds it early
Screening mammograms are an important way to find breast cancer before it causes any symptoms. Cancer found this way is often smaller and easier to treat. Talk with your doctor about when to start screening and how often, based on your age and your personal risk factors.
What to ask your team
If you notice a change, ask whether it needs a mammogram, an ultrasound, or a biopsy — a small tissue sample checked under a microscope. Ask when you should start or resume regular screening. Ask whether your family or personal history puts you at higher risk. And ask exactly which symptoms should prompt you to call before your next visit, rather than wait.
For more detail on specific next steps, see Is a Breast Lump a Sign of Cancer?, What Does BI-RADS 3 Mean?, What Does BI-RADS 4 Mean?, and Breast Cancer Treatment by Stage.
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Words to know
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Common questions
What is the most common sign of breast cancer?
The most common sign is a new lump or mass in the breast or underarm. A painless, hard lump with irregular edges is more likely to be cancer, but lumps can also be soft, tender, or rounded, so any new lump should be checked.
What other symptoms can occur?
Other possible signs include swelling or a change in breast size or shape, skin dimpling or puckering, redness or thickening of the skin, nipple pain or turning inward, and nipple discharge other than breast milk.
Do all breast changes mean cancer?
No. Many breast changes are caused by non-cancer conditions. But because some are signs of cancer, any new or lasting change should be evaluated by a doctor.
Can breast cancer be found before symptoms?
Yes. Screening mammograms can find breast cancer early, before it causes any symptoms, which is why regular screening is recommended for many people.
When should I see a doctor?
See a doctor if you notice a new lump, a change in the size or shape of a breast, skin or nipple changes, or nipple discharge. Getting new changes checked promptly is important.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
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Last updated: 2026-08-05Next planned review: 2027-07-07
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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