Breast cancer is the most common cancer in women worldwide, yet it is also one of the most treatable when it is caught early. It begins when cells in the breast start to grow and divide in an uncontrolled way, forming a lump or thickening that can, over time, spread to other parts of the body. The encouraging news is that decades of research have transformed how the disease is detected, classified, and treated, and survival keeps improving.
In this article you will learn what breast cancer is, its main types and risk factors, the warning signs worth checking, and how screening, imaging, and laboratory tests work together during diagnosis and follow-up. You will also see where blood tests fit, the latest scientific advances, and clear answers to common questions.
What breast cancer is
Breast cancer develops when abnormal cells in breast tissue multiply faster than the body can control them. Most tumours start in the milk ducts or in the lobules, the glands that produce milk. Some stay contained where they began, whilst others become invasive and can travel to nearby lymph nodes or distant organs.
Common types and subtypes
Ductal carcinoma in situ (DCIS) is an early, non-invasive form confined to the ducts. Invasive ductal carcinoma is the most frequent type, followed by invasive lobular carcinoma. Less common forms include inflammatory breast cancer, which can cause redness and swelling rather than a distinct lump.
Why receptor status matters
Doctors also classify tumours by what drives their growth. Laboratory tests on the biopsy sample check for oestrogen and progesterone receptors, known together as hormone receptors, and for a protein called HER2. A tumour that lacks all three is called triple-negative breast cancer, whilst hormone-receptor-positive and HER2-positive cancers each have their own targeted treatments. This molecular profile guides nearly every treatment decision.
Who is at risk: key risk factors
Anyone with breast tissue can develop breast cancer, including men, though it is far more common in women and the risk rises with age. Having a risk factor does not mean you will get the disease, and many people who are diagnosed have no obvious risk factor at all.
Family history and inherited genes
A close relative with breast or ovarian cancer raises your risk. Inherited changes in the BRCA1 and BRCA2 genes are the best-known example and also increase ovarian cancer risk. People with a strong family history may benefit from genetic counselling and testing.
Hormonal and reproductive factors
Longer lifetime exposure to oestrogen plays a role, including starting periods early, reaching menopause late, or using certain hormone therapies. When it is useful, laboratories can measure the oestradiol hormone level. For a wider picture of reproductive hormones, doctors may order a broader female hormone panel.
Lifestyle and modifiable factors
Being overweight after menopause, drinking alcohol, and physical inactivity are linked to higher risk, whilst regular activity appears protective. Research on weight and metabolism is active, and scientists recently examined the link between GLP-1 weight-loss drugs and breast cancer risk.
Signs and symptoms to watch for
Breast cancer can show up in different ways, and some early cancers cause no symptoms at all, which is exactly why screening matters. Knowing what is normal for your own body helps you notice changes worth checking.
Common breast changes
- A new lump or thickening in the breast or armpit
- A change in breast size, shape, or contour
- Skin dimpling, puckering, or an orange-peel texture
- Redness, warmth, or a rash on the breast
- Nipple changes, such as inversion, crusting, or unusual discharge
- Persistent pain in one spot that is unrelated to your cycle
When to see a doctor
Most breast changes are not cancer, but they should never be ignored. Contact a healthcare professional if you notice a new lump, skin or nipple changes, or discharge that is bloody or comes from one breast on its own. Prompt evaluation is the single most useful step you can take, because finding breast cancer early gives the widest range of treatment options.
Screening and diagnosis: how breast cancer is found
No single test diagnoses breast cancer on its own. Instead, doctors combine imaging, a tissue sample, and laboratory analysis to confirm the diagnosis and describe the tumour in detail.
Imaging: mammography, ultrasound, and MRI
Mammography, a low-dose breast X-ray, is the main screening tool and can reveal tumours before they can be felt. Ultrasound helps separate fluid-filled cysts from solid masses, and MRI adds detail in higher-risk situations or when findings are unclear.
Biopsy and receptor testing
A biopsy, in which a small sample of tissue is removed and examined under a microscope, is the only way to confirm breast cancer. The same sample is tested for hormone receptors and HER2, which define the subtype and shape treatment.
How the main tests compare
| Test | What it shows |
|---|---|
| Mammography | Screens for and locates suspicious areas before a lump can be felt |
| Breast ultrasound | Helps tell a solid mass from a fluid-filled cyst |
| Breast MRI | Adds detail for higher-risk patients or unclear findings |
| Biopsy | Confirms whether cells are cancerous, the definitive step |
| Receptor and HER2 testing | Identifies hormone-receptor and HER2 status to guide therapy |
Where blood tests fit
Blood tests do not diagnose breast cancer, and no routine blood test can rule it out. They play a supporting role: helping monitor known disease, checking overall health during treatment, and, in the case of genetic testing, estimating inherited risk. To put these proteins in context, you can read a dedicated guide to tumour markers.
| Blood test | How it is used in breast cancer care |
|---|---|
| CA 15-3 | May help track response in advanced disease; not used to screen or diagnose |
| Carcinoembryonic antigen (CEA) | Sometimes followed alongside CA 15-3 during monitoring |
| Complete blood count (CBC) | Checks blood cells and treatment safety, not the cancer itself |
| BRCA1/BRCA2 genetic test | Estimates inherited risk in selected people; does not detect a tumour |
During follow-up, oncologists track treatment response with the CA 15-3 tumour marker test. Alongside it, doctors sometimes follow the carcinoembryonic antigen (CEA) blood test. To watch for the side effects of chemotherapy, your care team will regularly review your full blood count. When inflammation needs checking, clinicians may also measure the C-reactive protein inflammation marker.
How breast cancer is treated
Treatment is tailored to the tumour’s type, stage, and molecular profile, as well as to your overall health and preferences. Most people receive a combination of therapies delivered by a multidisciplinary team.
Surgery and radiotherapy
Surgery removes the tumour, either as a lumpectomy that preserves most of the breast or a mastectomy that removes it. Radiotherapy often follows to lower the chance that cancer returns nearby.
Systemic treatments
Systemic therapies travel through the whole body. Chemotherapy uses drugs to destroy fast-dividing cells. Endocrine, or hormone, therapy blocks the oestrogen that fuels hormone-receptor-positive tumours. Targeted therapies act on specific features such as HER2, and immunotherapy helps the immune system attack certain cancers, especially triple-negative disease.
Latest scientific advances
Breast cancer research is moving quickly. The findings below come from recent peer-reviewed studies and are shared to inform, not to guide treatment, which should always be discussed with your care team.
Smarter targeted drugs for HER2-low tumours
A newer class of medicines called antibody-drug conjugates works like a guided delivery system, carrying chemotherapy straight to cancer cells. One of them, trastuzumab deruxtecan, helped patients whose tumours make only small amounts of HER2, a group once labelled HER2-negative and now described as HER2-low. What this means for you: a tumour feature that used to offer no target can now open a treatment door, which is one reason detailed lab testing of the biopsy matters.
CDK4/6 inhibitors in earlier disease
CDK4/6 inhibitors are pills that slow the machinery cancer cells use to divide. Long used in advanced hormone-receptor-positive cancer, they are increasingly studied after surgery in earlier, higher-risk disease to reduce the chance of return. What this means for you: for some hormone-driven cancers, adding one of these drugs to standard hormone therapy may further lower the risk of recurrence, a benefit still being confirmed with longer follow-up.
Immunotherapy for triple-negative breast cancer
Triple-negative breast cancer has historically had fewer targeted options. Adding an immunotherapy drug, pembrolizumab, to chemotherapy before surgery improved long-term outcomes in early-stage triple-negative disease. What this means for you: even this harder-to-treat subtype now has an approved approach that can improve survival, which underlines why knowing the exact subtype is so important.
Screening tailored to personal risk
Rather than the same schedule for everyone, researchers are testing risk-based screening, which sets the timing and type of imaging according to each person’s estimated risk. A large randomised trial found this personalised approach to be a workable alternative to yearly mammography. What this means for you: screening may increasingly be matched to your own risk rather than to your age alone.
Genetic and polygenic risk scores
Beyond the BRCA genes, scientists are combining many small genetic variations into a single polygenic risk score, a way of summarising inherited risk from across the genome. Studies show these scores can refine risk estimates, although they still need careful validation in large groups of people followed over time, known as cohorts. What this means for you: genetic tools may eventually help identify who benefits from earlier or additional screening, even if they are not yet ready to be used on their own.
Living with and after breast cancer
A breast cancer diagnosis affects daily life well beyond treatment, and support for both body and mind is a genuine part of care rather than an afterthought.
Follow-up and side effects
After treatment, regular check-ups watch for any recurrence and manage lasting effects such as fatigue, lymphoedema, or menopausal symptoms from hormone therapy. Blood tests during this phase mostly monitor general health and treatment safety rather than search for cancer.
Emotional wellbeing
Anxiety, changes in body image, and uncertainty are common and valid. Psychological support, patient groups, and rehabilitation such as physiotherapy and gentle exercise all help people rebuild strength and confidence. Good nutrition and staying active support recovery and long-term health.
Glossary
| Term | Definition |
|---|---|
| Ductal carcinoma in situ (DCIS) | An early, non-invasive cancer confined to the milk ducts. |
| Invasive ductal carcinoma | The most common breast cancer, which has grown beyond the duct into nearby tissue. |
| Hormone receptor | A protein for oestrogen or progesterone that, when present, can fuel tumour growth. |
| HER2 | A protein that can drive cancer growth; testing for it guides targeted treatment. |
| Triple-negative breast cancer | A subtype lacking estrogen receptors, progesterone receptors, and extra HER2. |
| BRCA1 and BRCA2 | Genes whose inherited changes raise breast and ovarian cancer risk. |
| Mammography | A low-dose breast X-ray used for screening and diagnosis. |
| Biopsy | Removal of a small tissue sample to confirm whether cells are cancerous. |
| Tumour marker | A substance, often measured in blood, that can reflect cancer activity but cannot diagnose it. |
| Metastasis | The spread of cancer from where it started to other parts of the body. |
Frequently asked questions
What are the first signs of breast cancer?
The most common first sign is a new, painless lump in the breast or armpit. Others include a change in breast size or shape, skin dimpling or an orange-peel texture, nipple inversion, or unusual discharge. Many early cancers cause no symptoms, which is why regular screening remains important even when you feel well.
Does breast cancer always cause a lump or pain?
No. Some breast cancers are found on a mammogram before any lump can be felt, and most are painless in the early stages. Inflammatory breast cancer may cause redness and swelling instead of a distinct lump. Because symptoms vary, any persistent breast change deserves medical attention rather than a wait-and-see approach.
Is breast cancer hereditary?
Most cases are not inherited. Around 5 to 10 per cent are linked to inherited gene changes, most often in the BRCA1 and BRCA2 genes. A strong family history of breast or ovarian cancer may justify genetic counselling, which can clarify your risk and whether earlier or extra screening is advised.
What are the stages of breast cancer?
Breast cancer is staged from 0 to IV. Stage 0 is non-invasive DCIS, stages I to III describe increasing tumour size and lymph node involvement, and stage IV means the cancer has spread to distant organs. Staging combines imaging, the biopsy, and sometimes surgery, and it guides the treatment plan.
Can a blood test detect breast cancer?
No routine blood test can diagnose or rule out breast cancer. Tumour markers such as CA 15-3 are mainly used to monitor known disease, not to screen healthy people. Diagnosis still relies on imaging and a biopsy. Blood work does, however, support safe treatment and overall health monitoring.
What is triple-negative breast cancer?
Triple-negative breast cancer lacks oestrogen receptors, progesterone receptors, and extra HER2 protein, so hormone and HER2-targeted therapies do not work against it. It is usually treated with chemotherapy and, increasingly, immunotherapy. Although it can be more aggressive, research is steadily expanding the options available.
Sources
- American Cancer Society, Breast Cancer overview, cancer.org
- Centers for Disease Control and Prevention, Breast Cancer Basics, cdc.gov
- Mayo Clinic, Breast cancer: Symptoms and causes, mayoclinic.org
- Bardia A, et al. Trastuzumab Deruxtecan after Endocrine Therapy in Metastatic Breast Cancer. New England Journal of Medicine, 2024. doi.org/10.1056/NEJMoa2407086
- Kang S, et al. HER2-Low Breast Cancer: Now and in the Future. Cancer Research and Treatment, 2024. doi.org/10.4143/crt.2023.1138
- Morrison L, et al. The CDK4/6 inhibitor revolution: a game-changing era for breast cancer treatment. Nature Reviews Clinical Oncology, 2023. doi.org/10.1038/s41571-023-00840-4
- Crown J, et al. Adjuvant ribociclib plus a nonsteroidal aromatase inhibitor in HR-positive/HER2-negative early breast cancer: 5-year NATALEE follow-up. ESMO Open, 2025. doi.org/10.1016/j.esmoop.2025.105858
- Schmid P, et al. Overall Survival with Pembrolizumab in Early-Stage Triple-Negative Breast Cancer. New England Journal of Medicine, 2024. doi.org/10.1056/NEJMoa2409932
- Esserman LJ, et al. Risk-Based vs Annual Breast Cancer Screening: The WISDOM Randomized Clinical Trial. JAMA, 2026. doi.org/10.1001/jama.2025.24784
- Yiangou K, et al. Polygenic score distribution differences across European ancestry populations: implications for breast cancer risk prediction. Breast Cancer Research, 2024. doi.org/10.1186/s13058-024-01947-x
Further reading
- Ovarian cancer: symptoms, causes, and testing
- CA 125: a guide to interpreting this blood marker
- Multi-cancer early detection tests: what the evidence shows
- Lung cancer: symptoms, diagnosis, and treatment
- Colorectal cancer: causes, symptoms, and treatment
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