Breast Cancer — Causes, Staging, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Breast cancer is the most commonly diagnosed cancer in women globally, accounting for 11.7% of all new cancer diagnoses and 2.3 million new cases annually (WHO 2020). It is the leading cause of cancer death in women worldwide, though 5-year survival exceeds 90% for localised early-stage disease, highlighting the critical role of early detection. Breast cancer arises from malignant transformation of epithelial cells in the breast ducts (ductal carcinoma — most common, ~80%) or lobules (lobular carcinoma). Tumours are classified by hormone receptor status (oestrogen receptor/ER and progesterone receptor/PR), HER2 protein overexpression, and grade, which together determine prognosis and guide treatment selection. Triple-negative breast cancer (ER-, PR-, HER2-negative), accounting for 10-15% of cases, is the most aggressive subtype with the fewest targeted treatment options. Men account for less than 1% of all breast cancer cases.

Most breast cancers are sporadic — arising from acquired somatic mutations in breast epithelial cells over a lifetime. Hereditary breast cancer accounts for 5-10% of cases: BRCA1 mutations confer a 55-72% lifetime risk (also high ovarian cancer risk); BRCA2 mutations a 45-69% lifetime risk; other genes include PALB2, CHEK2, ATM, and CDH1. Established risk factors include female sex (100x higher risk than men), advancing age (risk increases sharply after 50), personal or family history of breast cancer, early menarche (before 12), late menopause (after 55), nulliparity, first childbirth after age 30, long-term combined hormone replacement therapy (HRT), postmenopausal obesity (adipose tissue produces oestrogen), alcohol consumption (dose-dependent risk — each unit/day increases risk by approximately 7%), dense breast tissue on mammography, and prior chest wall radiation. Breastfeeding is protective (reduces lifetime oestrogen exposure).

Early breast cancer is frequently asymptomatic and detected only on screening mammography. Symptoms to be aware of include: a new painless lump or thickening in the breast or axilla (armpit), change in breast size or shape, skin changes — dimpling, puckering, or tethering (pulling inward), nipple changes — inversion, discharge (especially unilateral blood-stained discharge), nipple eczema (Paget's disease of the nipple), skin erythema or warmth (inflammatory breast cancer — an aggressive form presenting as diffuse breast redness and oedema mimicking mastitis), and persistent breast pain (uncommon but possible). Advanced disease may present with bone pain (skeletal metastases), breathlessness (pleural effusion, lung metastases), jaundice (liver metastases), or neurological symptoms (brain metastases). Any breast change persisting beyond 2-3 weeks warrants prompt medical assessment.

Triple assessment (clinical examination, imaging, tissue biopsy) is the standard diagnostic approach. Imaging: mammography is the primary screening and diagnostic tool (sensitivity 85%, lower in dense breasts); breast ultrasound evaluates focal abnormalities, distinguishes solid from cystic lesions, and guides biopsy — preferred in women under 35; MRI provides the most detailed assessment of extent of disease, multifocality, and contralateral breast. Core needle biopsy (CNB) under ultrasound or stereotactic guidance provides histological diagnosis, receptor status (ER/PR/HER2 by immunohistochemistry), and grade. Staging (TNM): Stage I (tumour less than 2 cm, node-negative); Stage II (tumour 2-5 cm or 1-3 axillary nodes); Stage III (locally advanced — skin/chest wall involvement or 4+ nodes); Stage IV (distant metastases). Genomic assays (Oncotype DX, MammaPrint) help assess chemotherapy benefit in early hormone receptor-positive disease.

Treatment is multidisciplinary and tailored to tumour biology, stage, and patient factors. Surgery: breast-conserving surgery (lumpectomy/wide local excision) followed by radiotherapy for suitable early-stage tumours; mastectomy (total breast removal) for larger tumours, multifocal disease, or patient preference — immediate reconstruction is widely offered. Sentinel lymph node biopsy replaces routine axillary clearance for clinically node-negative patients. Systemic therapy: Hormone receptor-positive (ER+) breast cancer: anti-oestrogen therapy is the cornerstone — tamoxifen (premenopausal) or aromatase inhibitors (anastrozole, letrozole — postmenopausal) for 5-10 years reduces recurrence by ~50%. CDK4/6 inhibitors (palbociclib, ribociclib) combined with endocrine therapy significantly improve outcomes in metastatic HR+ HER2- disease. HER2-positive: trastuzumab (Herceptin) plus pertuzumab plus chemotherapy is standard adjuvant therapy. Triple-negative: chemotherapy (anthracycline + taxane); pembrolizumab (immunotherapy) for PD-L1+ metastatic disease; olaparib for BRCA-mutated metastatic TNBC. Radiotherapy follows breast-conserving surgery and is used in node-positive mastectomy cases.

Untreated breast cancer progresses to locally advanced then metastatic disease. Bone metastases — the most common site in Stage IV disease — cause severe pain, pathological fractures, and hypercalcaemia. Brain metastases (occurring in 20-30% of HER2-positive and triple-negative breast cancers) cause headaches, cognitive impairment, seizures, and focal neurological deficits. Liver metastases cause progressive liver failure and jaundice. Lymphoedema from axillary node involvement or surgery affects 20-30% of patients, causing chronic arm swelling and infection risk. Locally advanced untreated cancer causes skin ulceration and fungating chest wall wounds requiring specialist wound care. Stage I 5-year survival is 99%; Stage IV is approximately 28% — underscoring the critical importance of early detection through screening.

Screening mammography is the most important preventive tool — recommended every 2-3 years for women aged 50-74 in most national guidelines, detecting cancer at an early curable stage. High-risk individuals (BRCA carriers, strong family history) should have annual MRI from age 25-30. Chemoprevention: tamoxifen (20 mg daily for 5 years) reduces breast cancer risk by 33% in high-risk postmenopausal women; exemestane and anastrozole are alternatives. BRCA carriers may elect risk-reducing surgery: bilateral risk-reducing salpingo-oophorectomy (reduces breast and ovarian cancer risk) or prophylactic bilateral mastectomy. Lifestyle modification: limit alcohol (below 14 units/week), maintain healthy weight, exercise regularly (150 minutes moderate activity per week), and breastfeed where possible. Know your breast baseline and report changes promptly.

See a doctor promptly — ideally within 2 weeks — if you notice any new breast lump, skin changes (dimpling, redness), nipple discharge (especially blood-stained or unilateral), nipple inversion, or persistent breast pain. Do not wait to see if it resolves. Inflammatory breast cancer presents as rapid onset breast redness, warmth, and swelling — this can be mistaken for mastitis, but if antibiotics do not resolve symptoms within 1 week, urgent specialist review is required. Any breast lump in a man requires urgent assessment. If you carry a BRCA mutation or have a strong family history, discuss earlier and more frequent screening with your oncology team. Bone pain, breathlessness, or new neurological symptoms in a breast cancer survivor warrant urgent oncology review to exclude metastatic disease.