What is Breast CancerBreast cancer is a disease in which abnormal cells in the breast grow uncontrollably and may invade nearby tissues or spread to other parts of the body. It is one of the most common cancers affecting women worldwide, although men can also develop breast cancer.
Most breast cancers begin in the milk ducts or lobules of the breast. These cancers are generally classified as carcinomas because they develop from epithelial cells. Less common breast malignancies, such as breast sarcomas, arise from connective or other supporting tissues.
Breast cancer can be classified as non-invasive or invasive:
Non-invasive breast cancer:Abnormal cells remain within their original location, such as the milk ducts, without invading surrounding breast tissue.
Invasive breast cancer:Cancer cells have spread beyond their original location into nearby breast tissue and may spread to lymph nodes or distant organs.
Breast cancer is not a single disease. Its biological characteristics, growth rate, treatment response and prognosis vary according to the cancer subtype, stage and individual patient factors.
Early breast cancer may not cause noticeable symptoms and is sometimes detected through screening mammography. Recognising changes in the breast and attending recommended screening appointments can help facilitate earlier diagnosis.
For more information, visit the National Cancer Institute's breast cancer overview.
Types of Breast Cancer
Breast cancer is classified according to where it originates, whether it has invaded surrounding tissue and its molecular characteristics. Identifying the type is important because it helps doctors select appropriate treatment.
Ductal Carcinoma in Situ (DCIS)
DCIS is a non-invasive condition in which abnormal cells are confined to the milk ducts. It is considered stage 0 breast cancer and has not invaded surrounding breast tissue. Treatment commonly involves breast-conserving surgery or mastectomy, with additional treatment considered according to individual risk.
Invasive Ductal Carcinoma (IDC)
IDC begins in the milk ducts and spreads into the surrounding breast tissue. It is the most common type of invasive breast cancer. Depending on its stage and biological features, treatment may involve surgery, radiotherapy and systemic therapies.
Invasive Lobular Carcinoma (ILC)
ILC begins in the milk-producing lobules and spreads into surrounding breast tissue. It may grow in a diffuse pattern, making it less noticeable as a distinct lump in some patients.
Other forms of breast cancer include:
Inflammatory breast cancer: An uncommon, aggressive type that may cause breast redness, swelling, warmth and skin thickening.
Paget disease of the breast: A rare condition involving the nipple and surrounding areola, often associated with an underlying breast cancer.
Medullary, mucinous and tubular carcinomas: Less common pathological types with different characteristics and prognoses.
Breast sarcoma: A rare malignancy arising from supporting tissues rather than the usual epithelial cells of the breast.
Doctors also classify breast cancer according to biomarkers identified through laboratory testing.
Hormone receptor-positive breast cancer (ER-positive and/or PR-positive)
These cancers have receptors for oestrogen and/or progesterone. Hormone therapy may help slow or prevent cancer growth by blocking hormone effects or reducing hormone production.
HER2-positive breast cancer
These cancers have increased HER2 protein activity, which can promote tumour growth. HER2-targeted medicines may be used as part of treatment.
Triple-negative breast cancer (TNBC)
TNBC lacks oestrogen receptors, progesterone receptors and HER2 overexpression. Hormone therapy and conventional HER2-targeted treatments are therefore not suitable for this subtype, although chemotherapy, immunotherapy and certain targeted medicines may be options in selected cases.
Read more about breast cancer types from the National Cancer Institute.
Breast Cancer Stages
Breast cancer staging describes the extent of the disease and helps guide treatment planning. Doctors use the TNM system, which assesses the primary tumour (T), regional lymph nodes (N) and distant metastasis (M).
The stage may also incorporate tumour grade and biomarkers such as ER, PR and HER2. Therefore, stage alone does not determine every treatment decision.
Stage 0 – Non-Invasive Breast Cancer
Stage 0 generally refers to DCIS, in which abnormal cells remain confined to the milk ducts without invading surrounding tissue. Treatment aims to reduce the risk of developing invasive breast cancer.
Stage I – Early Breast Cancer
Cancer is relatively small and may have no lymph node involvement or only limited involvement, depending on the specific stage classification. Treatment commonly includes surgery, with radiotherapy and systemic treatment considered according to tumour characteristics.
Stage II – Localised or Regional Breast Cancer
The tumour may be larger, or cancer may have spread to a limited number of nearby lymph nodes. Treatment may involve surgery, radiotherapy, chemotherapy, hormone therapy or targeted therapy, depending on the cancer subtype and individual circumstances.
Stage III – Locally Advanced Breast Cancer
Cancer may involve more extensive regional lymph nodes or nearby tissues, such as the skin or chest wall. Treatment often combines systemic therapy, surgery and radiotherapy. Medicines may be given before surgery to reduce tumour size.
Stage IV – Metastatic Breast Cancer
Cancer has spread to distant organs, such as the bones, liver, lungs or brain. Treatment generally focuses on controlling the disease, relieving symptoms, maintaining quality of life and prolonging survival. Treatment options depend on biomarkers, previous treatment and the patient's overall health.
Breast cancer treatment is individualised. Two patients with the same anatomical stage may receive different treatment because their tumour biology and medical circumstances differ.
For further details, see the American Cancer Society's breast cancer staging and treatment information.
Several factors may increase the likelihood of developing breast cancer. Having one or more risk factors does not mean that a person will necessarily develop the disease, and some patients have no identifiable risk factors.
Female Sex
Breast cancer occurs predominantly in women, although men can also develop the disease.
Increasing Age
The risk of breast cancer generally increases with age. However, younger people can also develop breast cancer.
Family History
Having a close relative with breast or ovarian cancer may increase risk, particularly when several relatives are affected or cancer develops at a young age.
Inherited Genetic Mutations
Inherited changes in genes such as BRCA1 and BRCA2 can substantially increase breast cancer risk. Genetic counselling and testing may be appropriate for selected individuals with a strong family history or other indicators of inherited susceptibility.
Reproductive and Hormonal Factors
Early menstruation, late menopause and certain reproductive histories can influence lifetime hormone exposure and may affect risk.
Obesity and Physical Inactivity
Excess body weight, particularly after menopause, and limited physical activity are associated with an increased risk of breast cancer in certain populations.
Alcohol Consumption
Alcohol intake is associated with increased breast cancer risk. Reducing or avoiding alcohol can help lower this particular risk.
Hormone Replacement Therapy
Some forms of menopausal hormone therapy, especially combined oestrogen-progestogen therapy, are associated with increased breast cancer risk. The effect varies by regimen and duration of use.
Pregnancy History
Having a first full-term pregnancy at a later age or never having a full-term pregnancy may influence breast cancer risk. These associations should not be interpreted as a reason to make reproductive decisions solely for cancer prevention.
Not all breast cancers can be prevented. However, maintaining a healthy weight, engaging in regular physical activity, limiting alcohol and discussing personal risk with a healthcare professional may help reduce risk.
People with a strong family history or inherited genetic risk may benefit from a personalised screening and prevention plan.
For more information, consult the American Cancer Society's breast cancer risk factors guide.
Early breast cancer may cause no noticeable symptoms. Some cases are identified through screening before a lump or other change develops.
Possible symptoms include:
Breast lump or thickening: A new lump or area of thickened tissue, which may or may not be painful.
Change in breast size or shape: A noticeable change that is not typical for the individual.
Skin dimpling or puckering: The breast skin may develop an uneven or pulled-in appearance.
Nipple inversion: A newly inverted or retracted nipple may require assessment.
Nipple discharge: Spontaneous discharge, particularly bloody discharge, should be evaluated.
Skin redness or scaling: Persistent changes affecting the nipple or breast skin may require investigation.
Breast swelling: Part or all of the breast may become swollen or enlarged.
Swollen lymph nodes: A lump or swelling in the armpit or near the collarbone may indicate lymph node involvement.
Inflammatory breast cancer may cause rapid breast swelling, redness, warmth and skin changes, sometimes without a distinct lump.
These symptoms do not automatically mean that someone has breast cancer. Benign conditions, infections and hormonal changes can produce similar findings. However, any new, persistent or unexplained breast change should be assessed by a healthcare professional.
Do not wait for pain to develop before seeking medical advice. Breast cancer can be painless, particularly in its early stages.
For additional information, see the National Cancer Institute's breast cancer symptoms guide.
How Is Breast Cancer Diagnosed?Breast cancer diagnosis involves a combination of medical history, clinical examination, imaging and tissue analysis. The exact investigations depend on the symptoms, examination findings and individual risk.
A doctor will ask about breast changes, symptom duration, personal medical history and family history. A clinical breast examination may be performed to assess lumps, skin changes, nipple abnormalities and nearby lymph nodes.
Breast self-awareness can help individuals recognise unusual changes, but self-examination alone cannot rule out breast cancer or replace recommended screening.
Mammography
Mammography uses low-dose X-rays to identify suspicious breast changes. It is used for screening and diagnostic assessment.
Breast Ultrasound
Ultrasound helps evaluate breast lumps and distinguish fluid-filled cysts from solid masses. It may also be used to guide a biopsy.
Breast MRI
MRI may be recommended for selected high-risk patients, complex diagnostic cases or assessment of disease extent. It is not necessary for every patient.
Core Needle Biopsy
A core needle biopsy removes small tissue samples from a suspicious area. It is commonly used to determine whether cancer is present and to assess its characteristics.
Fine Needle Aspiration
Fine needle aspiration collects cells or fluid using a thin needle. It can be useful in selected situations, but it does not always provide enough tissue to classify a breast tumour fully.
Surgical Biopsy
A surgical biopsy may be required when needle biopsy results are inconclusive or further tissue assessment is needed.
If breast cancer is confirmed, laboratory testing commonly assesses:
ER and PR status: Helps determine whether hormone therapy may be beneficial.
HER2 status: Helps identify patients who may benefit from HER2-targeted treatment.
Tumour grade and pathology: Provides information about the appearance and behaviour of cancer cells.
Genetic testing: May be considered when personal or family history suggests an inherited cancer predisposition.
Additional molecular tests: Selected patients may benefit from tests that help estimate recurrence risk or guide systemic treatment decisions.
Accurate diagnosis and biomarker assessment are essential because they influence treatment recommendations.
Breast cancer treatment depends on the stage, tumour subtype, biomarker results, risk of recurrence, previous treatment, overall health and personal preferences. Many patients receive a combination of local treatments and systemic therapies.
Treatment may be given before surgery to shrink a tumour, after surgery to reduce recurrence risk, or as the main approach for advanced disease.
Surgery aims to remove the cancer and, when indicated, assess nearby lymph nodes.
Breast-Conserving Surgery (Lumpectomy)
A lumpectomy removes the tumour and a margin of surrounding tissue while preserving most of the breast. Radiotherapy is commonly recommended afterward, although the need for additional treatment depends on individual clinical factors.
Mastectomy
A mastectomy removes the entire breast. It may be recommended when the tumour is extensive, multiple areas are affected, breast-conserving surgery is unsuitable or other clinical considerations favour removal of the breast.
Some patients may choose breast reconstruction or a flat closure after mastectomy. These options can be discussed with the surgical team.
Lymph Node Surgery
A sentinel lymph node biopsy may be used to assess whether cancer has spread to the first lymph nodes likely to receive drainage from the breast. Some patients require more extensive lymph node surgery, depending on the findings and treatment plan.
The choice between breast-conserving surgery and mastectomy depends on clinical suitability, expected outcomes and patient preference. Removing the entire breast is not always necessary.
Radiotherapy uses high-energy radiation to destroy cancer cells in a specific area. It is commonly used after breast-conserving surgery and may also be recommended after mastectomy for patients with particular risk factors.
The aim is to reduce the risk of cancer returning in the treated area. The need for radiotherapy, the treatment area and the schedule depend on the tumour characteristics and surgery performed.
Possible side effects include skin redness, fatigue, breast swelling or tenderness. Longer-term effects are possible but vary according to the treatment plan.
Chemotherapy uses medicines to kill cancer cells or prevent them from dividing. It can be administered before surgery to shrink a tumour or after surgery to reduce the risk of recurrence.
Chemotherapy may be recommended for certain higher-risk cancers, including some triple-negative and HER2-positive breast cancers, as well as selected hormone receptor-positive cancers.
Not everyone with breast cancer requires chemotherapy. The decision depends on factors such as tumour size, lymph node involvement, grade, biomarkers, recurrence risk and the likely benefit of treatment.
Common side effects may include fatigue, nausea, hair loss, reduced blood cell counts and increased susceptibility to infection. Side effects vary by medication, and supportive treatments can help manage many of them.
Hormone therapy, also called endocrine therapy, is used for breast cancers that express oestrogen receptors and/or progesterone receptors.
These medicines reduce hormone stimulation of cancer cells or block the effects of hormones. Treatment may be recommended after surgery to reduce recurrence risk or used to control advanced disease.
Examples include:
Tamoxifen: Blocks oestrogen receptors in breast tissue.
Aromatase inhibitors: Such as anastrozole, letrozole and exemestane, which reduce oestrogen production in appropriate patients.
Ovarian function suppression: May be combined with other endocrine treatment in selected premenopausal patients.
The appropriate medicine and duration depend on menopausal status, recurrence risk, treatment tolerance and other clinical factors.
Hormone therapy is not effective for every breast cancer subtype. It is generally used when the tumour has relevant hormone receptors.
Targeted therapy uses medicines that act on specific proteins, pathways or genetic changes involved in cancer growth.
HER2-Targeted Therapy
Patients with HER2-positive breast cancer may benefit from medicines that target the HER2 protein. These therapies may be combined with chemotherapy or other treatments, depending on the stage and treatment setting.
Other Targeted Medicines
Selected patients may benefit from targeted medicines directed at specific tumour features or genetic alterations, such as certain BRCA-related changes or pathways involved in hormone receptor-positive disease.
Biomarker and genetic test results help doctors determine whether a targeted medicine is appropriate. These treatments are not suitable for all patients and may have their own side effects.
Read more about targeted therapy for breast cancer from the National Cancer Institute.
Immunotherapy helps the immune system recognise and attack cancer cells. It may be used for selected patients with triple-negative breast cancer, depending on disease stage, biomarker results and the treatment setting.
For some patients, immunotherapy is combined with chemotherapy. It is not appropriate for every breast cancer subtype, and the expected benefits and potential immune-related side effects should be discussed with the treating team.
When breast cancer has spread to distant organs, treatment generally focuses on controlling disease, relieving symptoms, maintaining quality of life and extending survival.
Options may include hormone therapy, targeted therapy, chemotherapy, immunotherapy for selected cases, radiotherapy for symptom relief and other supportive treatments.
Treatment selection depends on the tumour's ER, PR and HER2 status, relevant genetic changes, previous therapies, symptoms and the patient's overall health.
Even when the disease cannot be cured, treatment may help control cancer for a period of time. Supportive and palliative care can also help manage symptoms and improve quality of life.
A personalised breast cancer treatment plan considers several factors:
Stage of disease: Whether cancer is confined to the breast, involves nearby lymph nodes or has spread to distant organs.
Tumour biology: ER, PR and HER2 status, along with other relevant pathological or molecular findings.
Recurrence risk: Tumour size, grade, lymph node involvement and other clinical or genomic information where appropriate.
Overall health: Other medical conditions, age, menopausal status and ability to tolerate treatment.
Patient preferences: Treatment goals, potential side effects, fertility considerations, quality of life and personal circumstances.
Patients should discuss the potential benefits, risks and alternatives of recommended treatments with their oncology team.
For a detailed overview, see the National Cancer Institute's breast cancer treatment guide.
Not all breast cancers can be prevented. However, maintaining a healthy weight, staying physically active, limiting alcohol and discussing individual risk factors with a healthcare professional may help reduce risk. People at elevated inherited risk may need a personalised screening or prevention plan.
Breast cancer outcomes vary according to the stage, tumour subtype, response to treatment and individual health factors. Many people with early-stage breast cancer can be treated successfully, while metastatic breast cancer generally requires ongoing disease management. Early assessment and appropriate treatment can improve outcomes.
Not every breast lump is cancerous. Cysts, fibroadenomas and other benign conditions can cause breast lumps. However, a new or suspicious lump may require imaging and, when indicated, a biopsy to establish the diagnosis.
Yes. Breast cancer can recur in the breast area, nearby lymph nodes or distant organs. The risk depends on the tumour characteristics, stage, treatment received and other factors. Follow-up appointments help monitor recovery, manage treatment effects and assess new symptoms.
Yes. Some breast cancers are detected by screening mammography before symptoms appear. The appropriate starting age and screening interval depend on local guidelines, individual risk and personal medical history. People at increased risk may require a different screening plan.
No. Some patients may be treated with surgery, radiotherapy, hormone therapy or targeted treatment without chemotherapy. Others benefit from chemotherapy because of their cancer subtype or recurrence risk. The decision should be based on an individual clinical assessment.
Yes. Although breast cancer is much less common in men, it can occur. A persistent breast lump, nipple changes or bloody nipple discharge in a man should be medically evaluated.
This article is intended for general health education only and should not replace professional medical advice, diagnosis or treatment. Breast cancer diagnosis and treatment should be guided by qualified healthcare professionals. Treatment options, benefits and risks vary according to individual circumstances. Anyone experiencing a suspicious breast change should seek medical assessment.
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