Questions and answers

Q1. What is breast cancer?

Breast cancer is cancer that starts in the breast tissue. It begins when abnormal cells in the breast grow in an uncontrolled manner and eventually form a growth (tumour). Breast cancer occurs when breast tumours spread. There is generally a long period between breast tissue changes and the development of breast cancer.

Q2. How common is breast cancer?

Breast Cancer is the most common cancer in the world. In the UK, approximately 55,000 women and 400 men are diagnosed with breast cancer every year. It’s estimated that 1 in 7 women and 1 in 870 men will develop breast cancer in their lifetimes.

Q3. What are the most common types of breast cancer?

Breast cancer is a diverse group of diseases. It may be invasive or non-invasive.

The most common types of invasive breast cancer include invasive breast cancer of no special type (NST), formally invasive ductal carcinoma which accounts for 70% of all invasive breast cancers and invasive lobular breast cancer which accounts for around 15% of all invasive breast cancers. Less common types include inflammatory breast cancer and Paget’s disease of the breast.

Breast cancers are classified into subtypes, according to hormone receptor status. Hormone receptor-positive breast cancers are those that have additional receptors for oestrogen, progesterone and/or human epithelial growth factor 2 (HER2). Oestrogen receptor-positive breast cancer accounts for around 75% of breast cancers. Triple-negative breast cancer has no additional receptors and accounts for around 15% of breast cancers. Non-invasive breast cancer is an early form of breast cancer, which remains localised to the breast. The most common form is ductal carcinoma in situ (DCIS).

Q4. What are the symptoms of breast cancer?

Breast cancer symptoms include:

• A new lump or thickening in your breast, upper chest or armpit.
• A change in the size, shape and feel of your breast.
• Skin changes in your breast such as puckering, dimpling, a rash or redness of the skin.
• Fluid leaking from the nipple in a woman who isn’t pregnant or breastfeeding.
• Changes in the position of the nipple, for example, it has become pulled in (inverted).
  9 out of 10 breast lumps are completely harmless. But if you spot any of these symptoms, we recommend contacting your GP.

For more information on how to check your breasts visit our breast check resource and sign up for our free monthly text reminder.

Q5. What should I do if I think I have breast cancer?

If you notice any symptoms of breast cancer, consult your GP. If they think your symptoms need further assessment, they’ll refer you to a specialist breast cancer clinic for further investigation.

Q6. How is breast cancer diagnosed?

Diagnosis is usually based on the results of a mammogram (breast X-ray) or an ultrasound scan (often used if you are under 35 years of age). You may also require a biopsy. A breast biopsy is where a sample of cells is taken from your breast and examined under a microscope, to see if there are abnormal or cancerous cells present.

Other investigations, such as a CT scan, may also be required before deciding on treatment.

Q7. What are the causes of breast cancer?

The causes of breast cancer are not fully understood, making it difficult to say why one person may develop the disease and another may not. However, studies have identified numerous factors which increase breast cancer risk (known as “risk factors”) including those associated with genetics, circulating hormone levels, lifestyle and environmental factors. Some of these risk factors you can influence, whilst others you have no control over.

For more information, please visit our prevention hub.

Q8. Is being overweight a breast cancer risk?

Yes, being overweight when women have reached the menopause is a significant risk factor for breast cancer. It is also a risk factor for men.

Q9. Is there a link between eating processed meat and breast cancer? 

Yes, there is convincing evidence that increased consumption of processed meats, such as bacon and salami, slightly increases breast cancer risk.

Q10. Can a healthy diet help to prevent breast cancer?

Yes, having a healthy diet can help prevent breast cancer.

Healthy eating includes:

• high consumption of fruit and vegetables, especially non-starchy vegetables (for example cruciferous vegetables such as broccoli) and foods high in carotenoids (for example sweet potato and carrots)
• eating food rich in vitamin D for adequate vitamin D levels in the body (for example fatty salmon or mushrooms)
• eating dairy products or dairy alternatives (without added sugar) which contain calcium and may contain beneficial bacterial cultures
• low or no consumption of red meat and processed meats
• low or ideally no alcohol
• not eating more than is needed, so you can maintain a healthy weight for your height

For further information please visit our Everyday Life IGuide

Q11. Does drinking alcohol increase my breast cancer risk?

Yes, drinking alcoholic beverages increases the risk of breast cancer in women and heavy drinking increases the risk in men. The more alcohol a woman consumes the greater the risk, with no lower threshold.

Q12. What is the ideal diet to decrease my risk of breast cancer?

There is no ideal diet for breast cancer prevention. It is more important to pay attention to the proportions of individual foods you consume.

Many diets can be healthy and help reduce your risk, including the Mediterranean diet, as well as balanced vegetarian diets. They all combine certain basic features for example no or low red meat consumption and a high proportion of fruit and vegetables.

Q13. Does eating a vegan or vegetarian diet decrease breast cancer risk?

There is insufficient evidence to be certain that vegetarians or vegans have a lower risk of developing breast cancer. However, many of the foods and eating patterns that make up a healthy vegan or vegetarian diet have been shown to reduce breast cancer risk, for example eating lots of fruits and non-starchy vegetables, replacing meat with plant-based protein sources like tofu, nuts, and legumes, and eating some dairy or dairy alternatives which provide calcium.

A vegetarian or vegan diet can also help keep a healthy weight or help those who need to lose weight, which is important for breast cancer prevention. Healthy foods eaten as part of a vegetarian or vegan diet are rich in fibre and tend to be lower in calories, fat, and protein compared to animal foods. However, the benefits of vegetarianism or veganism largely depend on the types of foods you eat and your overall dietary habits.

Q14. Does eating organic food decrease my risk of getting breast cancer?

The few human studies that have investigated the effects of organic food on breast cancer risk have so far yielded mixed results. However, eating organic food decreases pesticide exposure and exposure to certain pesticides may increase breast cancer risk. Examples include the insecticide malathion and the herbicide glyphosate. Pesticides and herbicides may act as mammary carcinogens or increase breast cancer risk by disrupting hormones, especially oestrogen.

Q15. Does drinking cow’s milk increase breast cancer risk?

There is insufficient evidence to conclude that drinking cow’s milk increases or decreases breast cancer risk. Evidence from several meta-analyses suggests a diet high in milk has no effect on breast cancer risk. A few meta-analyses suggest dairy products may reduce pre-menopausal breast cancer risk and have no effect on risk for women after menopause. Some observational studies found a diet high in cow’s milk increases risk, some find the opposite, whilst many others conclude cow’s milk does not alter risk.

Dairy products are high in calcium and vitamin D, which are protective against breast cancer.

Concerns that milk increases risk stem from the fact that cow’s milk usually comes from pregnant cows and contains high levels of bovine hormones, including bovine oestrogen. Drinking cow’s milk containing high levels of this hormone increases levels of human insulin growth factor 1 (IGF-1), and women with higher levels of IGF-1 have a slightly increased breast cancer risk. More research is needed to understand more clearly the impact cow’s milk has on breast cancer risk.

Q16. Does eating too much sugar increase breast cancer risk?

There is insufficient evidence to conclude that a diet high in sugar increases breast cancer risk, although some studies support this.

However, consuming large amounts of sugar can promote weight gain, often without the added benefit of vitamins and minerals, so-called “empty calories,” and being overweight or obese increases the risk of postmenopausal breast cancer and male breast cancer.

Q17. Can eating soy products increase breast cancer risk?

No, eating soy products does not increase breast cancer risk even though soy contains phytoestrogens. On the contrary, several recent studies that examined the effects of a soy-rich diet on breast cancer risk found there was a protective effect from soy and soy-based foods like tofu, but more research is needed to confirm this finding.

Q18: Does physical activity affect my risk of breast cancer?

Physical activity helps to lower breast cancer risk. It also helps prevent recurrence and mortality following a breast cancer diagnosis. Any type of additional physical activity is beneficial; the more the better. We recommend as a minimum following WHO guidelines.

Q19: Does smoking increase breast cancer risk?

Yes, smoking is thought to increase breast cancer risk slightly. Most (but not all) studies and meta-analyses conclude there is a modest increase in breast cancer risk for those who smoke, especially for pre-menopausal women and those who started smoking at a young age.

Q20. How might exposure to certain chemicals increase breast cancer risk? 

Everything is made up of chemicals, including us. However, some chemicals are harmful and damage our DNA; these are known as carcinogens. Others may be harmful as they can interfere with our hormones; these are knowns as endocrine (or hormone) disrupting chemicals (EDCs). Some EDCs can mimic the actions of the natural hormone oestrogen, which increases breast cancer risk.

For further details visit our Chemicals and the Environment IGuide

Q21. Where are endocrine-disrupting chemicals found?

Endocrine-disrupting chemicals or EDCs can be found in many everyday products such as cosmetics, kitchenware, plastic bottles, the lining of metal food cans, furniture and furnishings, electronics, toys, pesticides and food. They are present in air, soil and water.

They enter your body through eating, drinking, breathing and absorption through your skin.

Q22. Why don’t other cancer charities highlight exposures to harmful chemicals as cancer risk factors?

Most cancer charities choose to prioritise other, more well-established risk factors for breast cancer overexposure to chemicals of concern including endocrine-disrupting chemicals.

Some charities are not yet convinced that sufficient evidence is available to demonstrate harmful chemicals, such as oestrogen mimics, increase breast cancer risk. This is due to a lack of research into the effects of harmful chemicals on human health.

Whilst we support the valuable work they do, warnings from reputable scientists as well as bodies such as the United Nations Environment Programme, World Health Organisation and the Endocrine Society suggest that exposure to various EDCs does increase the risk of breast cancer.

At Breast Cancer UK, we adopt a precautionary approach. If there is scientific evidence that a chemical has a possible link to breast cancer, our advice is to avoid that chemical and call for its use to be restricted or banned so that everyone is more protected.

Q23. Does drinking water from plastic bottles increase breast cancer risk?

Some types of plastic bottles contain bisphenols (found in polycarbonate plastics) or phthalates (found in recycled PET plastic recycling code 1) which may be linked to an increased risk of breast cancer. It is unlikely that occasional exposure to such chemicals will result in breast cancer development. However, if plastic drinks bottles are used repeatedly, and especially if they are heated, these chemicals can leach out into liquids. Long-term exposure to these and other oestrogen mimics may contribute to increased breast cancer risk.

Q24. Do antiperspirants and deodorants increase breast cancer risk?

There is scientific evidence that endocrine-disrupting chemicals (EDCs) found in deodorants and antiperspirants may increase breast cancer risk. Most antiperspirants contain aluminium salts which some scientists believe may increase breast cancer risk. Other types of deodorants contain perfume and anti-microbial agents such as parabens; some of these are EDCs which may also be linked to breast cancer.

Single or infrequent exposure to any EDC is unlikely to increase breast cancer. However long-term exposure to oestrogenic EDCs, such as those found in antiperspirants, may be linked to increased risk.

Q25. Is breast cancer during pregnancy common?

Breast cancer during pregnancy, or pregnancy-associated breast cancer (PABC), is a condition defined as breast cancer diagnosed during pregnancy or in the first postpartum year.

Breast cancer during pregnancy is rare and occurs in around 1 in every 3,000 pregnancies.

Q26. How does age at the birth of a first child affect your breast cancer risk?

Women who have their first child under 30 years of age have a reduced overall lifetime risk of developing breast cancer. Women whose first full-term pregnancy occurs before the age of 20, have half the risk of breast cancer compared to those who never have children. Subsequent pregnancies increase protection against breast cancer.

The protective effect of pregnancy is not evident in women who have their first pregnancy between the ages of 30–34 years, and those who have their first pregnancy after 35 years of age are at an increased risk compared to those who don’t have children.

Although having children at a younger age lowers the long-term risk, the first pregnancy at any age increases the short-term risk of breast cancer. Women who have recently given birth have a short-term increase in breast cancer risk which peaks around 5 years after childbirth and continues for an average of 24 years.

Q27. Does breastfeeding reduce the risk of breast cancer?

Yes, breastfeeding lowers the risk of developing breast cancer. The longer you breastfeed the more risk is reduced. Although mechanisms are not fully understood, breastfeeding changes breast tissue by eliminating cells with DNA damage and reduces the lifetime number of menstrual cycles altering exposure to specific hormones which can influence breast cancer risk.

Q28. Does HRT cause breast cancer? 

Hormone replacement therapy, or HRT, increases breast cancer risk. The longer HRT is taken, the higher the risk.

For combined HRT (oestrogen and progestogen), when used discontinues increased risk declines but remains raised for many years. If combined HRT is taken for less than 1 year, the increased risk is no longer apparent once use has stopped.

Current use of oestrogen-only HRT increases risk. Past use of oestrogen-only HRT does not increase risk. Oestrogen creams do not appear to elevate risk.

Q29. Is it true that I’m more at risk if I don’t have children? 

Yes. Women who haven’t given birth have an increased risk of breast cancer, compared to those who’ve given birth before the age of 30. However, those who give birth over the age of 35 have a higher risk than those who don’t have children. Having more children at a younger age reduces risk even more.

Q30. If I’m on a contraceptive pill or another type of hormonal contraception am I at increased breast cancer risk?

The contraceptive pill contains synthetic oestrogen and synthetic progesterone (known as progestogen) or progestogen-only. Studies have shown the use of combined oral contraceptives (oestrogen and progestogen) slightly increases breast cancer risk. The risk is no longer evident 2 years after use has stopped. Some studies suggest certain progestogen-only contraceptives may not be associated with increased risk. More studies are needed to confirm this.

Other types of hormonal contraceptives include injections and hormone-releasing intrauterine systems which contain progestogen, and patches and vaginal rings which use both oestrogen and progestogen. There are fewer studies into risks associated with these types of contraceptives, although the risks are thought to be similar to the contraceptive pill.

Q31. Why are high levels of oestrogen potentially harmful?

Higher levels of circulating oestrogens are associated with an increased risk of breast cancer (this is also true for men). One explanation is that oestrogen encourages certain cell types, including breast cells, to divide more often. The more a cell divides, the more likely mutations will accumulate. The accumulation of particular mutations in breast cells can lead to breast cancer. Oestrogen also encourages the growth of oestrogen receptor-positive breast cancers.

Q32. Do transgender women have an increased risk of breast cancer?   

Yes, several studies have shown transgender women (those assigned male sex at birth who identify as women) who undergo hormone treatment have an increased risk of breast cancer compared to men who have not undergone treatment. However, transgender women are still less likely to develop breast cancer compared to women who have not undergone hormone treatment.

Q33. Do transgender men have an increased risk of breast cancer?   

No, there is no evidence that transgender men (those assigned female sex at birth who identify as men) who undergo hormone treatment are at an increased risk of breast cancer, compared to women (cis women) who have not undergone treatment. A Dutch study, based on a small sample size, found transgender men have a reduced risk compared to cis women but an increased risk compared to cis men. Many transgender men undergo a double mastectomy, which reduces breast cancer risk. Further studies are needed to assess the potential risks of long-term testosterone treatment.

Q34. Are there any ethnic groups in the UK more at risk of breast cancer?

Yes, some groups are more at risk than others, due to genetics or lifestyle factors. Individuals with an Ashkenazi Jewish background have a much higher risk of inheriting a BRCA gene mutation, compared to other members of the UK population. This increases their risk of breast cancer considerably (see here for more information).

Q35. Does a family history of breast cancer put someone at a higher risk?

Those who have inherited a specific gene mutation (e.g. a BRCA mutation) or with a strong family history of breast cancer (e.g. two first degree relatives (mother, sister, or daughter) or one first degree relative under 40 years who has had breast cancer) are at higher risk of getting the disease. Having one first-degree relative diagnosed with breast cancer approximately doubles your risk and risk is higher when you have a strong family history of the disease.

Having a BRCA mutation or a strong family history of breast cancer does not mean you will automatically get the disease; it means you are at higher risk. It should also be noted that most breast cancers occur in women who do not carry a single gene mutation or do not have a strong family history of the disease. Anyone can get breast cancer, although it is far more common in women of mature age.

Q36. What are BRCA1 and BRCA2 genes?

BRCA1 and BRCA2 (Breast Cancer genes 1 and 2) are genes that produce proteins that help repair damaged DNA and help prevent cancer developing. Every woman and man carries two copies of these genes. Those who inherit harmful variants (mutations) of either gene have an increased risk of several types of cancer, most notably breast and ovarian cancer. They also tend to develop cancer at a younger age. BRCA mutations can be inherited from either parent and each child of a parent carrying a BRCA mutation has a 1 in 2 chance of inheriting the mutation.

Q37. Is there a connection between breast cancer and ovarian cancer and are the causes the same?

There is occasionally a strong connection between breast and ovarian cancer when either is due to a single inherited gene mutation such as a mutation in a BRCA gene. This is known as “hereditary breast and ovarian cancer syndrome”. If either cancer is hereditary, then your risk is significantly increased for both cancers.

If your cancer is not hereditary (e.g. not due to a single inherited mutation), then there is a loose connection, based on both cancers sharing several common risk factors.

Q38. Why are taller women at a higher risk of getting breast cancer?

A study that included 5 million women found that being tall is a risk factor for hormone-responsive breast cancer. The reasons for this are not well understood.

It is likely that genetic factors and biological pathways which affect adult height may explain the association. For example, taller women have higher levels of insulin-like growth factor-1 (IGF-1), which also promotes cell division and inhibits programmed cell death (increasing cancer risk).  Cancer incidence increases with increasing adult height for most types of cancers.

Q39. Am I more at risk of breast cancer if I have breast implants?

There is no convincing scientific evidence to show implants increase breast cancer risk. However, breast implants may make breast cancer harder to detect.

There is also no evidence that breast reconstruction after cancer treatment carries an increased risk of breast cancer recurrence, whether or not implants are involved.  Certain types of “textured” breast implants (no longer available in the EU or UK) slightly increase the risk of a rare type of lymphoma.

Q40. Is stress a risk factor for breast cancer? 

It is unclear whether stress is a major risk factor for breast cancer.

A 2016 study of over 100,000 UK women found no association between breast cancers and stress. However, other studies have identified a link.

Q41. What does it mean to have dense breasts – is this a risk?

High breast (or mammographic) density is a risk factor for breast cancer. Breasts are described as “dense” if they have lots of fibrous or glandular tissue and not much fat tissue. The density of breast tissue can only be detected on a mammogram and is not related to the size of your breasts or how they feel. Breasts are naturally more or less dense (due partly to inheritance), although breast density does change over time, and breasts tend to become less dense with age.

Exposure to some EDCs (e.g. BPA) may increase breast density, especially if it occurs in the womb or during puberty. Dense breasts also make mammograms more difficult to interpret.

Q42. Does fluoride in drinking water increase breast cancer risk?

No studies have demonstrated a link between fluoride in drinking water and an increased risk of breast cancer. Fluoride is a substance added to drinking water to prevent tooth decay.

Q43. Does chlorine in drinking water increase breast cancer risk?

There is insufficient evidence to conclude that chlorine in drinking water increases breast cancer risk, although there are some studies that claim it could. Chlorine is added to water as a disinfectant.

Q44. Can mammograms increase the risk of breast cancer?

Mammograms deliver very low levels of ionising radiation, which will slightly increase breast cancer risk (estimated by the NHS to be 3-6 cancers per 10,000 women who are screened every 3 years from age 47 to 73).

Q45. Does socioeconomic status affect your risk of breast cancer?

Although breast cancer may affect people from all social backgrounds there are differences between socio-economic groups.  Women who live in areas of higher socioeconomic status have an increased risk of breast cancer, compared to those who live in more disadvantaged areas.

The reasons may be associated with reproductive and hormonal factors, such as later age at first childbirth, having fewer children and less breastfeeding, and certain lifestyle factors (see here for more information).

Q46. Does where you live affect your risk of breast cancer?

Women who live in wealthier countries have an increased risk of breast cancer, compared to those who live in poorer countries. The reasons may be associated with reproductive factors, such as earlier age at menarche (first period), later age at first childbirth, having fewer children, less breastfeeding, and lifestyle factors such as increased obesity, alcohol consumption, and reduced physical activity.

Living in urban areas, as opposed to rural areas, is also associated with increased risk. The reasons for this may be due to environmental factors such as increased levels of pollution in urban areas (see here for more information) or reproductive factors and lifestyle (see here for more information).

Q47. Do underwire bras increase my risk of breast cancer?

No, underwire bras do not increase your risk of breast cancer.

The claim is based on a suggestion that underwire bras block the drainage of lymph fluid from the bottom of the breast so it can’t get back into your body, but there is no reliable scientific evidence to support this claim.

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