The causes of breast cancer are not fully understood, making it difficult to say why one woman may develop breast cancer and another may not.
但是，已知有一些危险因素会影响您患乳腺癌的可能性。其中一些您无能为力，但是您可以更改一些。
年龄
The risk of developing breast cancer increases with age. The condition is most common in women over age 50 who have been through themenopause. About 8 out of 10 cases of breast cancer happen in women over 50.
All women who are 50 to 70 years of age should be screened for breast cancer every 3 years as part of the NHS Breast Screening Programme.
Women over the age of 70 are still eligible to be screened and can arrange this through their GP or local screening unit.
Find out more aboutbreast screening.
Family history
If you have close relatives who have had breast cancer orovarian cancer, you may have a higher risk of developing breast cancer.
但是，由于乳腺癌是女性最常见的癌症，因此可能会偶然发生多个家庭成员。
Most cases of breast cancer do not run in families, but genes known as BRCA1 and BRCA2 can increase your risk of developing both breast and ovarian cancer. It's possible for these genes to be passed on from a parent to their child.
TP53和CHEK2基因也与乳腺癌的风险增加有关。
如果乳腺癌或卵巢癌在您的家庭中进行，您担心您也可能会得到它，与GP交谈。他们可能会引用您进行NHS基因测试，这将告诉您您是否遗传了其中一个癌风险基因。
Find out more aboutpredictive genetic tests for cancer-risk genes.
以前的breast cancer or lump
If you have previously had breast cancer or early non-invasive cancer cell changes in breast ducts, you have a higher risk of developing it again, either in your other breast or in the same breast.
A良性乳房肿块does not mean you have breast cancer, but certain types of breast lumps may slightly increase your risk of developing cancer.
Some benign changes in your breast tissue, such as cells growing abnormally in ducts (atypical ductal hyperplasia), or abnormal cells inside your breast lobes (lobular carcinoma in situ), can make getting breast cancer more likely.
致密的乳房组织
Your breasts are made up of thousands of tiny glands (lobules) that produce milk. This glandular tissue contains a higher concentration of breast cells than other breast tissue, making it denser.
Women with dense breast tissue may have a higher risk of developing breast cancer as there are more cells that can become cancerous.
致密的乳房组织can also make a breast scan（乳房X线照片）difficult to read, as any lumps or areas of abnormal tissue are harder to see.
Younger women tend to have denser breasts. As you get older, the amount of glandular tissue in your breasts decreases and is replaced by fat, so your breasts become less dense.
Hormones and hormone medicine
Exposure to oestrogen
The female hormone oestrogen can sometimes stimulate breast cancer cells and cause them to grow.
The ovaries, where your eggs are stored, begin to produce oestrogen when you start puberty, to regulate your periods.
您患乳腺癌的风险可能会随着身体暴露的雌激素量而略有增加。
For example, if you started havingperiods在年轻的时候，更年期的时间比平均水平晚，您将在更长的时间内暴露于雌激素。
以同样的方式，没有孩子或以后生育孩子可能会稍微增加患乳腺癌的风险，因为您的雌激素暴露不会被怀孕打断。
Hormone replacement therapy (HRT)
Hormone replacement therapy (HRT)is associated with an increased risk of developing breast cancer.
All types of HRT can increase the risk of breast cancer, except for vaginal oestrogen.
如果您服用HRT少于1年，则不会增加患乳腺癌的风险。
但是，如果您服用HRT超过1年，则与从未使用HRT的女性相比，您患乳腺癌的风险更高。
The increased risk of breast cancer falls after you stop taking HRT, but some increased risk remains for more than 10 years compared to women who have never used HRT.
了解更多有关risks of HRT.
避孕药
Research shows that women who take thecontraceptive pill患乳腺癌的风险略有增加。
However, the risk starts to decrease once you stop taking the pill, and your risk of breast cancer is back to normal 10 years after stopping.
Cancer Research UK has more information aboutthe contraceptive pill and cancer risk.
Lifestyle factors
Being overweight or obese
If you have experienced the menopause and are overweight orobese, you may be more at risk of developing breast cancer.
This is thought to be linked to the amount of oestrogen in your body, as being overweight or obese after the menopause causes more oestrogen to be produced.
Alcohol
Drinking alcohol increases the risk of getting breast cancer.
People who drink even small amounts of alcohol on a regular basis have a greater risk of getting breast cancer than people who do not drink alcohol at all. The more alcohol you drink, the more your risk of getting breast cancer increases.
Radiation
Certain medical procedures that use radiation, such asX-rays和CT scans，可能会稍微增加患乳腺癌的风险。
If you hadradiotherapyto your chest area for霍奇金淋巴瘤您应该已经收到卫生和社会护理部的来信，邀请您与专家进行咨询，以讨论您患乳腺癌的风险增加。
See your GP if you were not contacted or if you did not attend a consultation. You're usually entitled to have your breast checked with an MRI scan.
If you currently need radiotherapy for Hodgkin lymphoma, your specialist should discuss the risk of breast cancer before your treatment begins.
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Page last reviewed: 28 October 2019
下一次审查应得：2022年10月28日