什么是筛查？
筛查是在一个人出现症状之前寻找疾病（例如乳腺癌）的迹象。筛查试验的目的是在癌症可以治疗并可能治愈的早期阶段发现癌症。有时筛查试验会发现非常小或生长非常缓慢的癌症。这些癌症在人的一生中不太可能引起疾病或死亡。
科学家们正试图更好地了解哪些人倾向于患哪种癌。例如，他们会调查年龄、家族史及一生中的某些暴露情况与癌症的关系。该类信息有助于医生建议哪些人应该接受癌症筛查，应采用哪些筛查方法以及筛查频率。
值得注意的是，医生建议您进行筛查，不一定是认为您得了癌症，因为筛查本身就是在癌症症状出现之前进行的检测。有强家族史、个人癌症史或其他危险因素的女性也可能会被建议接受基因检测。
如果筛查检查结果异常，则可能需要进行更多检查以确定是否患有癌症。这些检查称为诊断检查，而不再属于筛查检查。
有关癌症筛查的更多信息，请参阅以下PDQ总结：
What is screening?
Screening is looking for signs of disease, such as breast cancer, before a person has symptoms. The goal of screening tests is to find cancer at an early stage when it can be treated and may be cured. Sometimes a screening test finds cancer that is very small or very slow growing. These cancers are unlikely to cause death or illness during the person's lifetime.
Scientists are trying to better understand which people are more likely to get certain types of cancer. For example, they look at the person's age, their family history, and certain exposures during their lifetime. This information helps doctors recommend who should be screened for cancer, which screening tests should be used, and how often the tests should be done.
It is important to remember that your doctor does not necessarily think you have cancer if he or she suggests a screening test. Screening tests are done when you have no cancer symptoms. Women who have a strong family history or a personal history of cancer or other risk factors may also be offered genetic testing.
If a screening test result is abnormal, you may need to have more tests done to find out if you have cancer. These are called diagnostic tests, rather than screening tests.
See the following PDQ summary for more information about cancer screening:
乳腺癌概况
乳腺癌是一种在乳腺组织中形成恶性（癌）细胞的疾病。
乳腺由小叶和导管组成。每个乳腺有15~20个腺叶，每一腺叶分成若干个腺小叶。腺小叶末端是许多能够产生乳汁的腺泡。腺叶、腺小叶和腺泡通过被称为导管的细管相连。
女性乳房的解剖图。乳头和乳晕显示在乳房外侧。图中还显示了乳腺内部的淋巴结、乳腺叶、乳腺小叶、导管和其他部分。
乳房内也有血管和淋巴管。淋巴管输送一种几乎无色的水状液体，叫做淋巴。淋巴管在淋巴结之间运送淋巴。淋巴结是极小的豆状结构，可以过滤淋巴和储存用以帮助抵抗感染和疾病的白细胞。淋巴结群通常集中在乳房附近的腋窝（臂下）、锁骨上方和胸部。
有关乳腺癌的更多信息，请参阅以下PDQ总结：
乳腺癌是美国女性的第二大癌症死因。乳腺癌是中国女性的第五大癌症死因。
美国女性患乳腺癌高于除皮肤癌外任何其他类型的癌症。
乳腺癌发病风险通常随女性年龄的增长而升高。白人妇女比黑人妇女更易发生乳腺癌，但黑人妇女死于乳腺癌的几率比白人妇女高。
男性极少患乳腺癌。由于患乳腺癌的男性通常会出现明显的肿块，因此筛查意义不大。
不同影响因素会增加或降低患乳腺癌的风险。
有关乳腺癌的危险因素和保护因素的更多信息，请参阅《乳腺癌预防》中的PDQ总结。
General Information About Breast Cancer
Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.
The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.
Anatomy of the female breast. The nipple and areola are shown on the outside of the breast. The lymph nodes, lobes, lobules, ducts, and other parts of the inside of the breast are also shown.
Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless, watery fluid called lymph. Lymph vessels carry lymph between lymph nodes. Lymph nodes are small, bean-shaped structures that filter lymph and store white blood cells that help fight infection and disease. Groups of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.
See the following PDQ summaries for more information about breast cancer:
Breast cancer is the second leading cause of death from cancer in American women.
Women in the United States get breast cancer more than any other type of cancer except for skin cancer.
Breast cancer is more likely to occur as a woman ages. It occurs more often in white women than in black women, but black women die from breast cancer more often than white women.
Breast cancer rarely occurs in men. Because men with breast cancer usually have a lump that can be felt, screening tests are not likely to be helpful.
Different factors increase or decrease the risk of breast cancer.
For information about risk factors and protective factors for breast cancer, see the PDQ summary on Breast Cancer Prevention.
乳腺癌筛查
当一个人没有症状时，通过检测可筛查不同类型的癌症。
科学家们对各种筛查方法进行研究，以期找到危害最小、收益最大的筛查方法。癌症筛查试验的目的也包括明确早期发现（在癌症引起症状之前发现癌症）是否有助于延长寿命或降低死于该疾病的机率。对于某些类型的癌症，如果在早期发现并治疗，康复机率更大。
乳腺X线摄影是乳腺癌筛查最常用的检查方法。
乳腺X线摄影通过对乳房进行X线摄影，能够发现不可触及的肿瘤。这种方法也可以发现导管原位癌(DCIS)。导管原位癌的肿瘤细胞局限于乳腺导管。患有导管原位癌的部分患者会发展为浸润性癌。
乳腺X线摄影难以发现致密乳腺组织中的肿瘤。因为在乳腺X线片上，乳腺肿瘤和致密的乳腺组织均呈现为“白色”致密影，二者难以区分。年轻女性的乳腺腺体多为致密型。
乳腺X线摄影.拍摄时需将受检者的乳房放在两个夹板之间，通过X线摄影获取乳房的影像。
乳腺X线摄影能否检出（发现）乳腺癌受多种因素的影响。
对于50-69岁的女性，通过乳腺X线筛查可以降低乳腺癌死亡率。
在美国，死于乳腺癌的女性越来越少，这是因为筛查的早期发现而获益，还是因为治疗效果更好了，尚不清楚。
磁共振成像 (MRI) 可用于高危女性的乳腺癌筛查。
MRI利用磁场和无线电波，并经计算机处理获得图像。这一过程也称为核磁共振成像(NMRI)。MRI不使用X线照射，因此受检女性不会受到辐射损伤。
MRI可作为乳腺癌高危女性的筛查方法。女性乳腺癌的危险因素包括：
MRI比乳腺X线更有可能发现非恶性的乳腺肿块。
是否开展乳腺癌筛查以及选取何种筛查方法取决于多种因素。
具有乳腺癌危险因素的女性（如BRCA1或BRCA2基因突变，或患有某些遗传综合征）可以在较低年龄接受多次筛查。
曾接受过胸部放疗的年轻女性可更早接受常规乳腺癌筛查。对此类人群开展乳腺X线摄影和磁共振成像的利弊尚不清楚。
对于以下人群，尚无证据表明乳腺癌筛查可获益：
临床试验已经或正在开展针对其他筛查方法的研究。
为了明确不同筛查方法是否有助于发现乳腺癌或延长寿命，研究人员对以下方法开展了研究。
乳房触诊
临床乳房触诊是指由医生进行的乳腺视诊触诊检查。医生会仔细触诊乳房和腋下，寻找肿块或其他异常。目前尚不清楚临床乳房触诊能否降低乳腺癌死亡率。
乳房自检是指通过自我检查来发现乳房肿块或异常变化。如发现异常，请咨询您的医生。定期进行乳腺自检不能降低乳腺癌死亡率。
热成像
热成像技术利用可感应温度的特殊照相机来记录乳房皮肤的温度。肿瘤会引起体温的变化，可能被热成像图捕捉到。
目前还没有关于热成像技术的随机临床试验，这种方法的利弊尚不可知。
组织取样
乳腺组织取样是指从乳腺组织中取出细胞进行显微镜检查。作为乳腺癌筛查方法之一，乳腺组织取样是否能降低乳腺癌死亡风险，目前尚不得知。
乳腺癌筛查方法正在通过临床试验进行研究
NCI临床试验网站可以检索到NCI支持的临床试验信息。Clinical trials.gov网站可以检索到其他组织支持的临床试验信息。
Breast Cancer Screening
Tests are used to screen for different types of cancer when a person does not have symptoms.
Scientists study screening tests to find those with the fewest harms and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) helps a person live longer or decreases a person’s chance of dying from the disease. For some types of cancer, the chance of recovery is better if the disease is found and treated at an early stage.
Mammography is the most common screening test for breast cancer.
A mammogram is an x-ray picture of the breast. Mammography may find tumors that are too small to feel. It may also find ductal carcinoma in situ (DCIS). In DCIS, abnormal cells line the breast duct, and in some women may become invasive cancer.
Mammography is less likely to find breast tumors in women with dense breast tissue. Because both tumors and dense breast tissue appear white on a mammogram, it can be harder to find a tumor when there is dense breast tissue. Younger women are more likely to have dense breast tissue.
Mammography. The breast is pressed between two plates. X-rays are used to take pictures of breast tissue.
Many factors affect whether mammography is able to detect (find) breast cancer:
Women aged 50 to 69 years who have screening mammograms have a lower chance of dying from breast cancer than women who do not have screening mammograms.
Fewer women are dying of breast cancer in the United States, but it is not known whether the lower risk of dying is because the cancer was found early by screening or whether the treatments were better.
Magnetic resonance imaging (MRI) may be used to screen women who have a high risk of breast cancer.
MRI is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI). MRI does not use any x-rays and the woman is not exposed to radiation.
MRI may be used as a screening test for women who have a high risk of breast cancer. Factors that put women at high risk include the following:
An MRI is more likely than mammography to find a breast mass that is not cancer.
Whether a woman should be screened for breast cancer and the screening test to use depends on certain factors.
Women with risk factors for breast cancer, such as certain changes in the BRCA1 or BRCA2 gene or certain genetic syndromes may be screened at a younger age and more often.
Women who have had radiation treatment to the chest, especially at a young age, may start routine breast cancer screening at an earlier age. The benefits and risks of mammograms and MRIs for these women have not been studied.
Breast cancer screening has not been shown to benefit the following women:
Other screening tests have been or are being studied in clinical trials.
Studies have been done to find out if the following breast cancer screening tests are useful in finding breast cancer or helping women with breast cancer live longer.
Breast Exam
A clinical breast exam is an exam of the breast by a doctor or other health professional. He or she will carefully feel the breasts and under the arms for lumps or anything else that seems unusual. It is not known if having clinical breast exams decreases the chance of dying from breast cancer.
Breast self-exams may be done by women or men to check their breasts for lumps or other changes. If you feel any lumps or notice any other changes in your breasts, talk to your doctor. Doing regular breast self-exams has not been shown to decrease the chance of dying from breast cancer.
Thermography
Thermography is a procedure in which a special camera that senses heat is used to record the temperature of the skin that covers the breasts. Tumors can cause temperature changes that may show up on the thermogram.
There have been no randomized clinical trials of thermography to find out how well it detects breast cancer or the harms of the procedure.
Tissue sampling
Breast tissue sampling is taking cells from breast tissue to check under a microscope. Breast tissue sampling as a screening test has not been shown to decrease the risk of dying from breast cancer.
Screening tests for breast cancer are being studied in clinical trials.
Information about clinical trials supported by NCI can be found on NCI’s clinical trials search webpage. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.
乳腺癌筛查的危害
筛查可能会带来危害。
在女性一生中，并非所有的乳腺癌均会导致死亡或疾病，所以这类乳腺癌并不需要被检出或进行治疗。
是否参加筛查通常很难抉择。并非所有筛查都有用，而且多数都有害。在做任何筛查之前，您可能都想跟您的医生就筛查进行讨论，以了解筛查的危害，并了解筛查是否证实可以降低癌症死亡风险。
乳腺X线的危害包括以下几点：
筛查可能出现假阳性结果。
即使没有癌症，筛查也可能提示异常。假阳性结果（提示癌症但实际未患癌症）通常会引起更多的检查（如组织活检），后者同样存在风险。
当乳腺活检结果异常时，咨询另一个病理医生的意见，可能更加有助于乳腺癌的诊断。
大多数异常结果最终都不是癌症。假阳性结果在以下女性中较为常见：
首次乳腺X线筛查，比之后的筛查更可能出现假阳性。每10个只接受一次乳腺X线检查的女性，就有一个女性是假阳性。女性接受乳腺X线检查次数越多，出现假阳性的概率就越高。结合之前的乳腺X线检查结果，并与当前的结果进行比较分析，可以降低假阳性结果的风险。
放射科医生的技术也会影响假阳性结果的概率。
假阳性结果会导致更多的检测，并引发焦虑。
如果乳腺X线结果异常，可能要做更多的检查来诊断癌症。在诊断过程中，女性会变得很焦虑。即使是假阳性，最终诊断并不是癌症，这种结果也可能导致几天甚至几年的焦虑。
很多研究表明，因假阳性结果感到焦虑的女性，未来更有可能定期规律地接受乳腺筛查。
假阴性结果可能会延误诊断和治疗。
即使存在乳腺癌，但筛查结果可能显示正常。称之为假阴性结果。出现假阴性结果的女性可能会推迟就医，即使她已经出现症状。乳腺X线检查大约会漏诊五分之一的癌症。
假阴性结果在以下女性中较为常见：
女性发现乳腺癌后，通常会采取治疗。但治疗可能会带来副作用，也未必能改善健康或延长寿命。
乳腺X线筛查发现的某些乳腺癌可能永远不会引起健康问题或危及生命。对这些癌症的检出称之为过度诊断。当发现这些癌症时，治疗可能导致严重的副作用，而且不会延长寿命、改善健康。
乳腺X线筛查使乳房暴露在低剂量的辐射下。
高辐射剂量是乳腺癌的危险因素。乳腺X线筛查的辐射量非常低。50岁以后开始接受乳腺X线筛查的女性，其受到乳腺X线辐射的总体剂量很小。乳房较大或植有假乳的女性，在接受乳腺X线检查时可能受到稍微偏高的辐射量。
乳腺X线检查过程中可能会有疼痛或其他不适。
乳腺X线检查中，乳房被放置在两个夹板中间。加压乳房有助于获得更好的乳腺X光片。女性在乳腺X线检查时会感到疼痛或其他不适。疼痛程度可能取决于以下因素：
与您的医生谈论您的乳腺癌风险以及您的筛查需求。
与您的医生或其他卫生保健医师谈论您的乳腺癌风险，是否需要接受筛查，以及筛查的收益与伤害。在权衡利弊之后，您应该共同参与决策是否需要接受筛查。（更多信息请参阅PDQ“癌症筛查概述”汇总）
Harms of Breast Cancer Screening
Screening tests can have harms.
Not all breast cancers will cause death or illness in a woman's lifetime, so they may not need to be found or treated.
Decisions about screening tests can be difficult. Not all screening tests are helpful and most have harms. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the harms of the test and whether it has been proven to reduce the risk of dying from cancer.
The harms of mammography include the following:
False-positive test results can occur.
Screening test results may appear to be abnormal even though no cancer is present. A false-positive test result (one that shows there is cancer when there really isn’t) is usually followed by more tests (such as biopsy), which also have risks.
When a breast biopsy result is abnormal, getting a second opinion from a different pathologist may confirm a correct breast cancer diagnosis.
Most abnormal test results turn out not to be cancer. False-positive results are more common in the following:
False-positive results are more likely the first time screening mammography is done than with later screenings. For every ten women who have a single mammogram, one will have a false-positive result. The chance of having a false-positive result goes up the more mammograms a woman has. Comparing a current mammogram with a past mammogram lowers the risk of a false-positive result.
The skill of the radiologist also can affect the chance of a false-positive result.
False-positive results can lead to extra testing and cause anxiety.
If a mammogram is abnormal, more tests may be done to diagnose cancer. Women can become anxious during the diagnostic testing. Even if it is a false-positive test and cancer is not diagnosed, the result can lead to anxiety anywhere from a few days to years later.
Several studies show that women who feel anxiety after false-positive test results are more likely to schedule regular breast screening exams in the future.
False-negative test results can delay diagnosis and treatment.
Screening test results may appear to be normal even though breast cancer is present. This is called a false-negative test result. A woman who has a false-negative test result may delay seeking medical care even if she has symptoms. About one in 5 cancers are missed by mammography.
The chance of a false-negative test result is more common in women who:
Finding breast cancer may lead to breast cancer treatment and side effects, but it may not improve a woman's health or help her live longer.
Some breast cancers found only by screening mammography may never cause health problems or become life-threatening. Finding these cancers is called overdiagnosis. When these cancers are found, having treatment may cause serious side effects and may not lead to a longer, healthier life.
Mammography exposes the breast to low doses of radiation.
Being exposed to high radiation doses is a risk factor for breast cancer. The radiation dose with a mammogram is very low. Women who start getting mammograms after age 50 have very little risk that the overall exposure to radiation from mammograms throughout their lives will cause harm. Women with large breasts or with breast implants may be exposed to slightly higher radiation doses during screening mammography.
There may be pain or discomfort during a mammogram.
During a mammogram, the breast is placed between two plates that are pressed together. Pressing the breast helps to get a better x-ray of the breast. Some women have pain or discomfort during a mammogram. The amount of pain may also depend on the following:
Talk to your doctor about your risk of breast cancer and your need for screening tests.
Talk to your doctor or other health care provider about your risk of breast cancer, whether a screening test is right for you, and the benefits and harms of the screening test. You should take part in the decision about whether you want to have a screening test, based on what is best for you. (See the PDQ summary on Cancer Screening Overview for more information.)
About This PDQ Summary
About PDQ
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
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This PDQ cancer information summary has current information about breast cancer screening. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
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Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Updated") is the date of the most recent change.
The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Screening and Prevention Editorial Board.
Clinical Trial Information
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).
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The best way to cite this PDQ summary is:
PDQ® Screening and Prevention Editorial Board. PDQ Breast Cancer Screening. Bethesda, MD: National Cancer Institute. Updated
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About This PDQ Summary
About PDQ
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
PDQ is a service of the NCI. The NCI is part of the National Institutes of Health (NIH). NIH is the federal government’s center of biomedical research. The PDQ summaries are based on an independent review of the medical literature. They are not policy statements of the NCI or the NIH.
Purpose of This Summary
This PDQ cancer information summary has current information about breast cancer screening. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
Reviewers and Updates
Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Updated") is the date of the most recent change.
The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Screening and Prevention Editorial Board.
Clinical Trial Information
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).
Permission to Use This Summary
PDQ is a registered trademark. The content of PDQ documents can be used freely as text. It cannot be identified as an NCI PDQ cancer information summary unless the whole summary is shown and it is updated regularly. However, a user would be allowed to write a sentence such as “NCI’s PDQ cancer information summary about breast cancer prevention states the risks in the following way: [include excerpt from the summary].”
The best way to cite this PDQ summary is:
PDQ® Screening and Prevention Editorial Board. PDQ Breast Cancer Screening. Bethesda, MD: National Cancer Institute. Updated
Images in this summary are used with permission of the author(s), artist, and/or publisher for use in the PDQ summaries only. If you want to use an image from a PDQ summary and you are not using the whole summary, you must get permission from the owner. It cannot be given by the National Cancer Institute. Information about using the images in this summary, along with many other images related to cancer can be found in Visuals Online. Visuals Online is a collection of more than 3,000 scientific images.
Disclaimer
The information in these summaries should not be used to make decisions about insurance reimbursement. More information on insurance coverage is available on Cancer.gov on the Managing Cancer Care page.
Contact Us
More information about contacting us or receiving help with the Cancer.gov website can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the website’s E-mail Us.