Breast cancer !

Breast cancer is a malignant tumour that starts in the milk ducts or lobules of the breast; it is the most common cancer in women.

Updated 2026-10-30

Structures involved

Tap one to see what it is and open it in 3D.

In biochemistry

In immunology

Lymph node: cortex, paracortex, medulla

In histology

In the clinical exam

In physiology

Actions of estrogen and progesterone

Why it happens

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What it is

Malignant tumour arising from the epithelial cells of the breast's ducts or lobules. It is the most common cancer in women; it also occurs, rarely, in men.

Who gets it

The most frequent cancer and a leading cause of cancer death in women in Colombia and Latin America; incidence rises with age. In a meta-analysis of 63 studies (221,255 women diagnosed 1966–2017), 40.8% of cases in Latin America and the Caribbean were found at stage III–IV. About 1% of cases occur in men.

Causes

Accumulated genetic and epigenetic changes in ductal or lobular cells
Hormonal stimulation (oestrogen and progesterone) of breast tissue
Inherited mutations (e.g. BRCA1, BRCA2) in a minority of cases

Risk factors

Female sex and older age
Family history or inherited mutations (BRCA1/2)
Early menarche, late menopause, no pregnancies or first pregnancy after 30
Menopausal hormone therapy
Obesity after menopause, alcohol and physical inactivity
Previous chest radiation or atypical hyperplasia

Pathophysiology

Breast cancer usually begins in the terminal duct–lobular unit. Carcinoma in situ stays within the basement membrane; invasive carcinoma breaks through it and can spread by lymphatics to the axillary and internal mammary (parasternal) nodes and by blood to bone, lung, liver and brain. Hormone receptor and HER2 status define biological subtypes that guide treatment.

Classification

In situ (ductal, DCIS) vs invasive (ductal/no special type, lobular)
Molecular subtypes: luminal A and B (hormone receptor positive), HER2-positive, triple negative
TNM staging (0–IV)

Symptoms and signs

Painless, hard, irregular lump
Skin dimpling or retraction (Cooper ligament involvement)
Nipple retraction or bloody discharge
Peau d'orange skin or redness (inflammatory breast cancer)
Axillary lump
Often no symptoms when found on screening

Diagnosis

Clinical: Triple assessment: clinical examination, imaging and tissue biopsy. History includes family history and hormonal factors.
Tests: Core needle biopsy with histology and receptor status: oestrogen receptor (ER), progesterone receptor (PR) and HER2. Genetic counselling and testing in selected patients; staging bloods.
Imaging: Mammography (and ultrasound, especially in young women or dense breasts); MRI in selected cases. Staging with CT and bone scan in advanced disease. Screening mammography starts at ages that vary between guidelines.

Differential diagnosis

Fibroadenoma
Breast cyst
Fibrocystic breast changes
Fat necrosis
Breast abscess or mastitis
Phyllodes tumour

Goal of treatment

Remove the tumour with clear margins, stage and treat the axilla, lower the risk of recurrence with systemic therapy chosen by subtype, and preserve quality of life and body image.

Treatment

Surgical: Breast-conserving surgery (followed by radiotherapy) or mastectomy, with breast reconstruction when appropriate.
Surgical: Axillary staging with sentinel lymph node biopsy; axillary dissection when nodes are involved, per guidelines.
Medical: Endocrine therapy for hormone-receptor–positive tumours (selective oestrogen receptor modulators, aromatase inhibitors).
Medical: Chemotherapy and HER2-targeted antibodies by subtype and stage, before (neoadjuvant) or after surgery.
Procedure: Radiotherapy after breast-conserving surgery and in selected cases after mastectomy.
Follow-up: Multidisciplinary follow-up with clinical review and annual mammography, plus survivorship and psychological support.

Drugs for this condition

Complications

Local recurrence
Metastases to bone, lung, liver and brain
Lymphoedema of the arm after axillary treatment
Treatment effects: cardiotoxicity, bone loss, early menopause
Psychological impact

Prognosis

Early-stage, hormone-receptor–positive disease has a very good prognosis. Outlook depends on stage, nodal status, grade and subtype; triple-negative and late-diagnosed disease do worse.

Prevention

Screening mammography in eligible women per national guidelines
Healthy weight, physical activity and limited alcohol
Breastfeeding
Genetic counselling and risk-reducing options for high-risk carriers

Test yourself

Think of the answer, then tap the question to see it.

What is the triple assessment of a breast lump?

Clinical examination, imaging (mammography and/or ultrasound) and tissue biopsy, usually core needle biopsy.

Which three receptors are tested in breast cancer and why?

Oestrogen receptor, progesterone receptor and HER2; they define subtype, prognosis and eligibility for endocrine or HER2-targeted therapy.

Which lymph nodes receive most of the breast's lymphatic drainage?

The axillary nodes; medial parts of the breast also drain to the internal mammary (parasternal) nodes.

What causes skin dimpling over a breast cancer?

Tumour infiltration and shortening of the suspensory (Cooper) ligaments, which pulls the skin inwards.

Can men develop breast cancer?

Yes. It is rare (about 1% of cases), often presents as a lump behind the nipple, and is linked to BRCA2 mutations and high oestrogen states.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Breast Cancer (StatPearls (NCBI Bookshelf), 2024); Stage at diagnosis and stage-specific survival of breast cancer in Latin America and the Caribbean: A systematic review and meta-analysis (PloS one, 2019) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.

Parasternal lymph nodes highlighted on the Durgical 3D model