Editing Breast cancer (section)

== Screening ==
{{Main|Breast cancer screening}}

[[File:MammographyinprocessGraphic.jpg|thumb|Cartoon of a mammogram, with the breast to be imaged pressed between two plates.]]

Breast cancer screening refers to testing otherwise-healthy women for breast cancer in an attempt to diagnose breast tumors early when treatments are more successful. The most common screening test for breast cancer is low-dose [[X-ray]] imaging of the breast, called [[mammography]].<ref name=NCI-PDQ>{{cite web|url=https://www.cancer.gov/types/breast/patient/breast-screening-pdq |accessdate=5 January 2024 |publisher=National Cancer Institute |title=Breast Cancer Screening PDQ – Patient Version |date=26 June 2023}}</ref> Each breast is pressed between two plates and imaged. Tumors can appear unusually dense within the breast, distort the shape of surrounding tissue, or cause small dense flecks called [[microcalcification]]s.<ref>{{cite web|url=https://www.komen.org/breast-cancer/screening/mammography/mammogram-images/ |accessdate=5 January 2024 |title=Findings on a Mammogram and Mammogram Results |publisher=Susan G. Komen Foundation |date=30 November 2022}}</ref> Radiologists generally report mammogram results on a standardized scale – the six-point [[Breast Imaging-Reporting and Data System]] (BI-RADS) is the most common globally – where a higher number corresponds to a greater risk of a cancerous tumor.{{sfn|Nielsen|Narayan|2023|loc="Interpretation of a Mammogram"}}{{sfn|Metaxa|Healy|O'Keeffe|2019|loc="Introduction"}}

A mammogram also reveals breast density; dense breast tissue appears opaque on a mammogram and can obscure tumors.<ref>{{cite web|url=https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/understanding-your-mammogram-report.html |accessdate=8 January 2024 |publisher=American Cancer Society |title=Understanding Your Mammogram Report |date=14 January 2022}}</ref><ref>{{cite web|url=https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/breast-density-and-your-mammogram-report.html |accessdate=8 January 2024 |publisher=American Cancer Society |title=Breast Density and Your Mammogram Report |date=28 March 2023}}</ref> BI-RADS categorizes breast density into four categories. Mammography can detect around 90% of breast tumors in the least dense breasts (called "fatty" breasts), but just 60% in the most dense breasts (called "extremely dense").{{sfn|Nielsen|Narayan|2023|loc="Implications of Breast Density"}} Women with particularly dense breasts can instead be screened by [[ultrasound]], [[magnetic resonance imaging]] (MRI), or [[tomosynthesis]], all of which more sensitively detect breast tumors.{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Screening"}}

[[File:Mammo breast cancer wArrows.jpg|thumb|[[Mammograms]] showing a normal breast (left) and a breast with cancer (right)]]

Regular screening mammography reduces breast cancer deaths by at least 20%.{{sfn|Loibl|Poortmans|Morrow|Denkert|2021|loc="Screening"}} Most [[medical guideline]]s recommend annual screening mammograms for women aged 50–70.{{sfn|Hayes|Lippman|2022|loc="Screening for Breast Cancer"}} Screening also reduces breast cancer mortality in women aged 40–49, and some guidelines recommend annual screening in this age group as well.{{sfn|Hayes|Lippman|2022|loc="Screening for Breast Cancer"}}{{sfn|Rahman|Helvie|2022|loc="Table 1"}} For women at high risk for developing breast cancer, most guidelines recommend adding MRI screening to mammography, to increase the chance of detecting potentially dangerous tumors.{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Screening"}} Regularly feeling one's own breasts for lumps or other abnormalities, called [[breast self-examination]], does not reduce a person's chance of dying from breast cancer.<ref>{{cite web|url=https://www.cancer.gov/types/breast/hp/breast-screening-pdq |accessdate=10 January 2024 |publisher=National Cancer Institute |title=Breast Cancer Screening (PDQ) - Health Professional Version |date=7 June 2023}}</ref> Clinical breast exams, where a health professional feels the breasts for abnormalities, are common;{{sfn|Menes|Coster|Coster|Shenhar-Tsarfaty|2021|loc="Abstract"}} whether they reduce the risk of dying from breast cancer is not known.<ref name=NCI-PDQ/> Regular breast cancer screening is commonplace in most wealthy nations, but remains uncommon in the world's poorer countries.{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Screening"}}

Still, mammography has its disadvantages. Overall, screening mammograms miss about 1 in 8 breast cancers, they can also give [[False positives and false negatives|false-positive]] results, causing extra anxiety and making patients overgo unnecessary additional exams, such as [[Biopsy|bioposies]].<ref>{{Cite web |title=Limitations of Mammograms {{!}} How Accurate Are Mammograms? |url=https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/limitations-of-mammograms.html |access-date=2024-10-28 |website=www.cancer.org |language=en}}</ref>