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Overview

What Is Breast Cancer?

Breast cancer is a group of diseases in which cells in the breast grow abnormally and may form a tumor. It can begin in different breast tissues, including the milk ducts or lobules, and some tumors can spread to nearby lymph nodes or distant organs. Breast cancer affects people of any sex, although it is much more common in women. In medical terms, many breast cancers are carcinomas of the breast, or malignant neoplasms of the breast.

Symptoms

Breast Cancer Symptoms and Signs

  • A new lump or area of thickening in the breast or underarm should be checked, even if it is not painful.
  • A change in breast size, shape, or appearance may be a sign of a condition that needs evaluation.
  • Skin dimpling, puckering, or an orange-peel-like texture warrants medical assessment.
  • Redness, scaling, irritation, or thickening of the breast skin or nipple should be evaluated if it persists.
  • A nipple that turns inward or produces unexpected discharge, especially bloody discharge, should be assessed.
  • Persistent, localized breast pain should be discussed with a healthcare professional.
  • Swelling near the underarm or collarbone may reflect enlarged lymph nodes and should be checked.

WHEN TO GET CHECKED

Do not wait for pain

Breast cancer may not cause pain, itching, or any noticeable symptom early on. Many breast changes are caused by conditions other than cancer, but a new or persistent change should not be self-diagnosed or ignored.

These symptoms can occur in women and men. A healthcare professional should assess any new, persistent, or changing finding in the breast, nipple, chest, or underarm; symptoms alone cannot confirm or rule out breast cancer.

Causes

What Causes Breast Cancer?

Breast cancer begins when genetic changes cause breast cells to grow and divide without normal controls. These abnormal cells can accumulate and form a tumor, and some tumors can invade nearby tissue or spread elsewhere. Breast cancers can arise through different molecular pathways, so the precise cause is often not identifiable in one individual. Risk factors can increase the likelihood of disease, but they are not the same as a single direct cause.

Inherited and acquired genetic changes

Inherited mutations, such as changes in BRCA1 or BRCA2, are present from birth and can raise breast cancer risk, but most breast cancers result from acquired changes that develop during a person’s lifetime. Breast cancer is not contagious and is not caused by ordinary contact, touching, or sharing food. Factors such as age, family history, hormone exposure, and lifestyle may affect risk without guaranteeing that someone will develop the disease.

Risk Factors

Breast Cancer Risk Factors

Risk factor groupExamplesWhat patients should know
Less modifiableOlder age, female sex, dense breasts, and a personal history of breast cancerThese factors cannot usually be changed, but they can help guide screening and risk discussions.
Inherited and family-relatedA close family history or inherited gene changes such as BRCA1 or BRCA2Family history is not the same as an inherited mutation, and genetic counseling may clarify risk.
Reproductive and hormonalLonger lifetime exposure to estrogen, some hormone therapies, and certain reproductive factorsThe effect varies by the type, timing, and duration of exposure; discuss personal risks with a clinician.
Potentially modifiableAlcohol use, physical inactivity, and excess body weight after menopauseReducing alcohol, being active, and maintaining a healthy weight when possible may lower risk, but cannot prevent every case.
Medical and environmental contextPrior chest radiation and some medical historiesIndividual risk depends on the specific exposure or condition and may warrant earlier or additional assessment.

Side Effects & Complications

Breast Cancer Complications and Treatment Side Effects

Possible disease complications

  • Local disease can invade nearby breast or chest-wall tissues and may require more extensive treatment.
  • Cancer cells can involve lymph nodes in the underarm or near the collarbone.
  • Breast cancer can recur in the breast, chest wall, nearby tissues, or elsewhere after treatment.
  • Metastatic breast cancer has spread to distant organs such as bone, liver, lungs, or brain and requires ongoing disease management.
  • Fatigue may occur during or after cancer treatments and can affect daily activities.
  • Nausea or appetite changes can occur with some chemotherapy, targeted treatments, or other medicines.
  • Hair loss may occur with some chemotherapy regimens and usually depends on the specific medicine.
  • Radiation or medicines may cause skin changes such as redness, dryness, irritation, or sensitivity.
  • Some treatments can lower infection-fighting blood cells and increase infection risk.
  • Hormone therapies and chemotherapy may cause hot flashes, menstrual changes, or other menopausal symptoms.
  • Nerve irritation or neuropathy can cause numbness, tingling, or pain in the hands and feet.
  • Lymphedema can cause swelling in an arm, breast, or chest area after lymph-node treatment.
  • Some treatments can affect fertility, so fertility preservation should be discussed before treatment when relevant.
  • Emotional distress, anxiety, depression, or changes in body image may occur during or after treatment.

GET MEDICAL HELP

Report serious or rapidly worsening effects

Contact your care team promptly for fever, sudden swelling, shortness of breath, uncontrolled pain, severe allergic symptoms, or rapidly worsening treatment effects. Use emergency services when symptoms are severe or life-threatening.

Diagnosis & Staging

Breast Cancer Diagnosis and Staging

  • A clinical breast examination checks the breast, chest, underarm, and nearby areas for concerning changes.
  • A diagnostic mammogram uses detailed X-ray images to investigate a symptom or abnormal screening result.
  • Ultrasound can help distinguish fluid-filled areas from solid tissue and guide evaluation of a finding.
  • Breast MRI may be recommended for selected people when additional imaging is needed.
  • A biopsy removes a sample of tissue so a pathologist can determine whether cancer is present.
  • Laboratory analysis identifies tumor biomarkers, including hormone receptors and HER2, that help guide treatment.

What breast cancer stages mean

Staging describes how far the cancer has developed and helps guide treatment planning. Stage 0 refers to noninvasive disease confined to its original tissue, while stages I through III generally describe invasive cancer with increasing tumor extent or lymph-node involvement; stage IV means distant spread. Doctors also consider tumor size, lymph nodes in the breast region, grade, hormone-receptor and HER2 findings, and sometimes other molecular features. Stage is important, but it does not promise a specific outcome.

Disease extentGeneral meaningRole in treatment planning
LocalizedCancer is confined to the breast or has limited local involvement.Treatment often focuses on removing or destroying the tumor and lowering the chance of recurrence.
RegionalCancer has reached nearby tissues or regional lymph nodes but not distant organs.Treatment may combine local therapy with systemic treatment based on tumor features and risk.
MetastaticCancer has spread to distant organs and is also called stage IV disease.Treatment generally focuses on controlling cancer, relieving symptoms, preserving function, and supporting quality of life.

Treatment Options

Breast Cancer Treatment Options

SURGERY

Surgery removes the tumor, part of the breast, or the whole breast when appropriate, and may include evaluation or removal of lymph nodes.

RADIATION THERAPY

Radiation uses focused energy to destroy remaining cancer cells, often after breast-conserving surgery or for selected advanced disease.

CHEMOTHERAPY

Chemotherapy uses medicines that travel through the body and may be given before surgery, after surgery, or for advanced disease.

HORMONE THERAPY

Hormone therapy slows or blocks hormone signals in cancers with estrogen or progesterone receptors.

TARGETED THERAPY

Targeted medicines act on specific features of cancer cells, such as HER2, and are used when testing shows the relevant target.

IMMUNOTHERAPY

Immunotherapy helps the immune system recognize or attack cancer and may be considered for selected subtypes, including some triple-negative breast cancers.

When treatments are given

Treatment may be given before surgery to shrink a tumor, after surgery to reduce recurrence risk, or as the main approach for advanced or metastatic breast cancer. Some therapies are used to relieve symptoms or protect function when cure is not possible. A plan may combine several breast cancer treatments and is based on stage, subtype, biomarkers, overall health, and personal goals.

Prevention & Screening

Breast Cancer Prevention and Screening

  • Regular physical activity may help lower breast cancer risk and supports overall health.
  • Limiting alcohol can reduce one modifiable breast cancer risk factor.
  • Avoiding tobacco supports general health, although the relationship between tobacco and breast cancer is complex.
  • Maintaining a healthy weight when possible, particularly after menopause, may reduce risk.
  • Discuss the benefits and risks of hormone therapy with a healthcare professional before starting or continuing it.
  • Breastfeeding when feasible may provide a modest reduction in breast cancer risk.
Risk groupTypical screening discussionWhy individualized advice matters
Average riskMammography is discussed according to age, risk, country, and current guideline recommendations.Schedules and starting or stopping ages differ, so follow local guidance and personal medical advice.
Higher riskEarlier specialist assessment and additional breast MRI or other imaging may be recommended for some people.Family history, inherited mutations, prior chest radiation, and breast density can change the screening plan.
A new symptom or findingDiagnostic evaluation may include examination, mammography, ultrasound, MRI, or biopsy rather than routine screening alone.Screening is for people without symptoms; a new change requires timely clinical evaluation.

SCREENING REMINDER

Know your normal

Breast self-awareness can help people notice a new change, but it does not replace recommended mammography or clinical evaluation. Breast cancer awareness activities support education and early action, not a substitute for medical care.

Outlook and Prognosis

Breast Cancer Outlook and Prognosis

Many breast cancers can be treated successfully, especially when found before distant spread, but prognosis differs substantially among individuals. The outlook depends on stage, tumor grade, receptor and molecular subtype, response to treatment, overall health, and whether the cancer returns. Metastatic breast cancer is generally treated as a long-term condition focused on control, symptom relief, and quality of life.

Stage-specific

Survival estimates should be interpreted by stage and population.

Subtype-specific

Receptor status and tumor biology affect outlook and treatment response.

Time-dependent

Statistics are based on people treated in earlier periods and may change as care improves.

Not personal predictions

Population statistics cannot predict one person's outcome.

Survivorship & Follow-up

Breast Cancer Survivorship and Follow-up

  • Scheduled follow-up visits help review recovery, treatment effects, medications, and ongoing care needs.
  • Breast or chest imaging is performed when indicated by treatment history, symptoms, and clinical guidance.
  • Taking prescribed medicines as directed and discussing barriers supports ongoing treatment goals.
  • Treatment effects such as pain, fatigue, neuropathy, menopausal symptoms, or lymphedema should be managed with the care team.
  • Follow-up includes monitoring for recurrence and assessing new symptoms rather than assuming every change is cancer.
  • A survivorship care plan can summarize treatment history, follow-up needs, and health priorities.

Changes to report between visits

Tell your oncology team about a new lump, persistent bone or chest pain, unexplained weight loss, breathlessness, neurological changes, or ongoing swelling. These symptoms can have many causes, but they deserve timely assessment, particularly after breast cancer treatment.

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Symptoms

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