Breast Cancer: Risk Factors, Diagnosis and Treatment

Breast Cancer: Risk Factors, Diagnosis and Treatment

Breast cancer occurs when cells in the breast tissue grow and divide abnormally, forming a tumour. It is the most frequently diagnosed cancer in women globally and a leading cause of cancer death in women worldwide. It also occurs in men, though rarely — accounting for less than 1% of all breast cancer cases.

Outcomes are generally better when breast cancer is found before it has spread. US SEER data for women diagnosed in 2016–2022 report five-year relative survival of 100.0% for localised disease, 87.5% for regional disease and 33.8% for distant disease. Relative survival compares a population with the general population; a rounded 100.0% is not a guarantee of survival or cure for every patient. These US summary-stage groups are not the same as TNM stages I–IV.

How Breast Cancer Develops

Most breast cancers begin in the milk ducts (ductal carcinoma) or the milk-producing glands (lobular carcinoma). Over time, abnormal cells can invade surrounding breast tissue and ultimately spread to lymph nodes and distant organs through the lymphatic and blood vessel systems.

In Situ (Non-Invasive) vs Invasive Cancer

• Ductal carcinoma in situ (DCIS) — cancer cells are confined within the milk duct and have not invaded surrounding tissue; highly treatable and often detected on screening mammography
• Invasive ductal carcinoma (IDC) — the most common form (~80% of all breast cancers); cancer has breached the duct wall and entered surrounding breast tissue
• Invasive lobular carcinoma (ILC) — cancer originates in the lobules and spreads to adjacent tissue; often presents with diffuse thickening rather than a discrete lump

Risk Factors

Non-Modifiable Risk Factors

Age — risk increases steadily with age. The majority of breast cancers are diagnosed in women over 50; the median diagnosis age is 63. However, younger women are not protected — about 7% of cases occur under age 40.

Genetic mutations — BRCA1 and BRCA2 gene mutations are present in less than 1% of women but account for 5–10% of all breast cancers. NCI estimates lifetime breast-cancer risk above 60% for women with an inherited harmful BRCA1 or BRCA2 variant; the estimate varies by gene, family history and other factors. Not every BRCA change is harmful, so a result needs genetic counselling. Other genes including PALB2, CHEK2, ATM and TP53 also increase risk.

Family history — a first-degree relative (mother, sister or daughter) with breast cancer roughly doubles the risk; two or more first-degree relatives raise it three to four times.

Prior breast cancer — a personal history of breast cancer in one breast raises the risk of cancer in the other breast by approximately 0.4% per year.

Reproductive factors:

• Early menarche (first period before age 12)
• Late menopause (after age 55)
• First full-term pregnancy after age 30
• Never having been pregnant
• These factors increase cumulative lifetime oestrogen exposure

Dense breast tissue — increases both the risk of breast cancer and the difficulty of detecting it on mammography.

Prior radiation to the chest — particularly during adolescence (e.g. for Hodgkin lymphoma).

Modifiable Risk Factors

Factor	Effect on Risk
Alcohol consumption	Risk increases with amount; even 1 drink/day raises risk by ~10%
Obesity (postmenopausal)	Adipose tissue produces oestrogen; raises risk 20–40%
Physical inactivity	Increases risk; regular exercise is protective
Combined HRT (oestrogen + progestogen)	Modest increase in risk during and shortly after use
Smoking	Modest increase, particularly with long-term heavy use

Symptoms

Most early breast cancers cause no symptoms and are detected on routine mammography. When symptoms occur, they include:

• A painless lump or area of thickening in the breast or armpit
• Change in breast size, shape or contour
• Skin changes — dimpling, puckering, redness, or a texture resembling orange peel
• Nipple changes — inversion, discharge (especially blood-stained), or ulceration
• Persistent breast pain (rare as the only symptom of cancer)

A lump that is hard, irregular in shape, and fixed rather than mobile carries a higher probability of malignancy. However, most breast lumps are benign — the majority are cysts, fibroadenomas, or fibrocystic changes.

Any new breast change should be assessed by a clinician promptly.

Diagnosis

Mammography

Mammography (low-dose breast X-ray) is the primary screening tool. It detects cancers typically 2–3 years before they become palpable.

Screening recommendations vary by country. Most guidelines recommend annual or biennial mammography from age 40–50 onwards. Women with BRCA mutations or strong family history begin screening earlier and often include annual MRI.

Limitations: mammography is less sensitive in women with dense breasts; supplemental ultrasound or MRI is sometimes used.

Ultrasound

Useful for characterising a lump found on examination or mammography — distinguishing a fluid-filled cyst from a solid mass. Also guides biopsy.

Breast MRI

More sensitive than mammography; used for high-risk screening, pre-surgical planning, and when mammography results are equivocal.

Biopsy

A tissue sample is essential for definitive diagnosis. Options include:

• Core needle biopsy — a hollow needle removes small cylinders of tissue; performed under local anaesthetic, usually ultrasound-guided; the standard approach
• Fine needle aspiration (FNA) — less tissue obtained; used primarily for cyst drainage or lymph node assessment
• Surgical biopsy (excision) — used when needle biopsy is non-diagnostic or the lesion is too small to target

Receptor and Genetic Testing

The biopsy specimen is tested for:

Marker	Significance
Oestrogen receptor (ER)	Positive in ~75% of cancers; drives hormone therapy eligibility
Progesterone receptor (PR)	Usually co-positive with ER
HER2 overexpression	Present in ~15–20%; drives HER2-targeted therapy
Ki-67	Proliferation marker; helps classify tumour aggressiveness

Examples of marker-based clinical groups used in treatment planning are listed below. These are simplified descriptions, not gene-expression-defined intrinsic molecular subtypes:

• Luminal A-like (ER+, HER2−, low Ki-67) — often has a more favourable prognosis. Endocrine therapy may be sufficient as the systemic component for selected early cancers; this does not replace indicated surgery or radiotherapy
• Luminal B-like (ER+, with either HER2− and high Ki-67, or HER2+) — more aggressive; may require chemotherapy
• HER2-positive, ER-negative (ER−, HER2+) — HER2-targeted treatment is considered according to stage and other clinical factors
• Triple-negative (ER−, PR−, HER2−) — treatment may include chemotherapy, immunotherapy, PARP inhibitors for eligible inherited BRCA-associated disease, or antibody-drug conjugates in specific settings. Choice depends on stage, biomarkers and prior treatment; PD-L1 requirements for pembrolizumab differ between early and advanced disease.

Staging

TNM staging defines spread:

Stage	Broad description
0	DCIS only
I	Early invasive disease
II	Greater tumour size and/or regional nodal involvement
III	Locally advanced disease
IV	Distant metastases (for example bone, liver, lung or brain)

This is an orientation to stage, not a staging calculator. Full staging also considers tumour biology and other findings. The dated SEER figures above use different stage groups and cannot be assigned directly to these TNM rows.

Sentinel lymph node biopsy is the standard for assessing nodal spread without full axillary clearance — reducing the risk of lymphoedema.

Treatment

Surgery

• Breast-conserving surgery (lumpectomy/wide local excision) — removes the tumour with a clear margin of normal tissue; followed by radiotherapy; equivalent survival to mastectomy for most early-stage cancers
• Mastectomy — removal of the entire breast; may be appropriate for extensive disease or patient preference. BRCA1/2 carriers should discuss breast-conserving treatment versus mastectomy, including future cancer risks and surveillance; carrier status alone does not make one operation mandatory
• Breast reconstruction — immediate or delayed; using implant or autologous tissue (e.g. TRAM flap, DIEP flap)

Radiotherapy

• Standard after breast-conserving surgery to eliminate residual microscopic disease
• Used after mastectomy in high-risk cases (large tumours, involved margins, extensive node disease)
• Modern techniques: intensity-modulated radiotherapy (IMRT) and proton therapy reduce dose to heart and lung

Hormone (Endocrine) Therapy

For ER-positive cancers:

• Tamoxifen — blocks oestrogen receptors; used for 5–10 years; reduces recurrence by ~40%; suitable for pre- and postmenopausal women
• Aromatase inhibitors (letrozole, anastrozole, exemestane) — reduce oestrogen production; more effective than tamoxifen in postmenopausal women
• CDK4/6 inhibitors (palbociclib, ribociclib, abemaciclib) — used with endocrine partners such as an aromatase inhibitor or fulvestrant in eligible HR-positive, HER2-negative advanced or metastatic disease. Some agents also have specific early-stage adjuvant indications; eligibility, partner medicine and local authorisation are product-specific

Chemotherapy

Used in:

• High-risk early-stage cancers (large tumours, node-positive, high Ki-67, triple-negative)
• HER2-positive cancers (combined with targeted therapy)
• As neoadjuvant (pre-surgery) treatment to shrink the tumour
• As palliative treatment in metastatic disease

Common regimens: anthracyclines (doxorubicin) ± cyclophosphamide, followed by taxanes (docetaxel, paclitaxel).

HER2-Targeted Therapy

For HER2-positive cancers:

• Trastuzumab (Herceptin) — the first and most established; dramatically improves outcomes in early and metastatic HER2+ disease
• Pertuzumab — combined with trastuzumab and chemotherapy for higher-risk disease
• T-DM1 (ado-trastuzumab emtansine) — an antibody-drug conjugate with US indications including HER2-positive early disease when invasive cancer remains after preoperative taxane/trastuzumab treatment, and specified previously treated metastatic disease
• Tucatinib-containing combinations — the US indication for previously treated advanced HER2-positive disease, including brain metastases, combines tucatinib with trastuzumab and capecitabine. A separate FDA approval dated 7 October 2026 permits tucatinib with trastuzumab and pertuzumab as maintenance after induction treatment for eligible unresectable advanced disease. These are different regimens; the oncology team must select the applicable one.

Immunotherapy

Pembrolizumab (anti-PD-1) has US indications for selected advanced TNBC with qualifying PD-L1 expression in combination treatment, and for high-risk early TNBC with chemotherapy before surgery followed by pembrolizumab after surgery. Early-disease eligibility does not require PD-L1 positivity. The exact label, test threshold, regimen and patient suitability must be checked locally.

PARP Inhibitors

Olaparib has US indications for eligible HER2-negative breast cancer with an inherited harmful BRCA variant, including high-risk early disease following chemotherapy and selected metastatic disease. Talazoparib has a US breast-cancer indication for inherited BRCA-associated, HER2-negative locally advanced or metastatic disease; the early high-risk adjuvant indication should not be attributed to both drugs. Prior treatment and the exact product label matter. US approval does not establish approval or availability in China.

Breast Cancer Treatment in China

Before travelling, ask the receiving team to review the pathology, ER/PR/HER2 results, stage and treatment already received. Confirm whether further imaging, biopsy review, genetic counselling or molecular testing is indicated rather than assuming every test is needed.

Ask about multidisciplinary review, surgical and reconstruction options, radiotherapy and systemic treatment appropriate to your situation. Reconstruction timing and drug access depend on clinical suitability and the institution. Obtain a written plan and itemised hospital quotation, and confirm language support and any PriumCare coordination separately.

Contact a PriumCare care navigator to arrange a breast cancer assessment, second opinion, or treatment consultation.

---

Sources and editorial correction

• NCI: breast cancer treatment.

• NCI: BRCA risk and testing.

• SEER: female breast cancer statistics, 2016–2022 survival cohort.

• WHO: global cancer burden.

• NCI: T-DM1.

• NCI: tucatinib and FDA: separate maintenance indication, 7 October 2026.

• NCI: pembrolizumab.

• NCI: olaparib.

• US talazoparib prescribing information.

• Additional targeted source.

• Additional targeted source.

Second-pass editorial clarification: 25 October 2026. Additional checks addressed the specific definitions, treatment eligibility and risk-classification statements documented here. This does not constitute a whole-article medical review.

Editorial source correction: 25 October 2026. Targeted checks addressed drug/regimen eligibility, BRCA risk, survival denominators and unsupported service claims. This is not a clinical review of the whole article. No named medical reviewer is claimed. Original publication date is retained.

---

Targeted editorial source check — 26 October 2026: Only the marker-based grouping paragraph was checked to distinguish clinical receptor descriptions from intrinsic gene-expression subtypes, using NCI professional treatment information, original receptor-versus-intrinsic-subtype research and ESMO clinical-surrogate terminology. This is not a whole-article medical review, adds no named clinical reviewer and retains the original publication date.