Mammogram — Purpose, Procedure & Normal Values | MyMedicPlus

A mammogram is a specialised low-dose X-ray of the breast used to detect and evaluate breast tissue changes, with a particular focus on identifying early breast cancer before symptoms develop. Modern digital mammography and 3D tomosynthesis (digital breast tomosynthesis, or DBT) acquire multiple thin-slice images of the breast from different angles, which are reconstructed into a three-dimensional representation. This significantly improves detection of small tumours — as small as 2–3 mm — reduces false recall rates by 15–40% compared to conventional 2D mammography, and improves the detection of invasive cancers in dense breast tissue. Mammography is considered the gold standard for breast cancer population screening and is used alongside clinical breast examination, ultrasound, and breast MRI when additional evaluation is required. Annual screening mammography reduces breast cancer mortality by approximately 20–30% through early detection.

Mammograms are ordered for routine population screening to detect breast cancer before symptoms appear, for diagnostic evaluation of a breast lump, nipple discharge, breast pain, unexplained skin or contour changes, peau d'orange appearance, or axillary lymph node enlargement discovered on clinical examination. Surveillance mammography is recommended for women with a personal history of breast cancer, a first- or second-degree relative with breast or ovarian cancer, a confirmed BRCA1 or BRCA2 gene mutation, prior chest radiation therapy (e.g., mantle field radiotherapy for Hodgkin lymphoma), or a history of atypical hyperplasia or lobular carcinoma in situ on previous biopsy. Screening guidelines vary: most major bodies recommend annual or biennial mammograms starting at age 40–50. Women at high risk (lifetime risk >20%) may begin at age 25–30, often with supplemental breast MRI.

No fasting is required for a mammogram. Schedule the appointment for the week following your menstrual period when breast tissue is least tender and swollen, improving both comfort and image quality. On the day of the test, do not apply deodorant, antiperspirant, perfume, talcum powder, or body lotion to the underarm area or breasts — metallic particles in these products can produce artefacts on the X-ray image that mimic calcifications. Wear a two-piece outfit so that only your top needs to be removed. Bring all previous mammogram images, reports, or CD/digital records to allow direct comparison with prior studies, as this significantly improves diagnostic accuracy and reduces unnecessary recalls. Inform the radiographer if you are pregnant, breastfeeding, have breast implants, or have had prior breast surgery. If you have implants, a specialised implant-displacement view (Eklund technique) will be used.

You stand in front of the mammography machine. A trained female radiographer (mammographer) positions one breast at a time onto a flat X-ray platform (image receptor). A moveable compression paddle then presses the breast firmly and evenly — this is essential to spread overlapping breast tissue, improve image sharpness, equalise tissue thickness across the field, reduce the radiation dose required, and improve detection of small lesions. Two standard views are taken for each breast: the cranio-caudal (CC) view from above and the mediolateral oblique (MLO) view at an angle. For 3D tomosynthesis, the X-ray tube moves in an arc during the exposure. Each compression lasts approximately 10–15 seconds and may cause mild to moderate temporary discomfort. Additional views (spot compression, magnification) may be taken during diagnostic mammography. The entire appointment including check-in typically takes 15–20 minutes.

Mammogram results are reported using the ACR BI-RADS (Breast Imaging Reporting and Data System) classification, a standardised seven-category system: BI-RADS 0 — Incomplete, additional imaging or prior comparison needed before assessment; BI-RADS 1 — Negative, no abnormality identified, routine screening continues; BI-RADS 2 — Benign finding (cyst, calcified fibroadenoma, intramammary lymph node), normal screening interval; BI-RADS 3 — Probably benign (<2% malignancy risk), 6-month short-interval follow-up recommended; BI-RADS 4A/B/C — Suspicious (low to high concern), tissue sampling (biopsy) recommended; BI-RADS 5 — Highly suspicious of malignancy (>95% likelihood), biopsy required before treatment; BI-RADS 6 — Known biopsy-proven malignancy awaiting treatment. Being recalled for additional views after a screening mammogram is common — approximately 10% of women screened for the first time — and does not usually indicate cancer. Most callbacks result in a benign or normal outcome.

The radiation dose from a mammogram is very low — approximately 0.4 mSv per breast for a two-view digital examination, equivalent to roughly 7 weeks of natural background radiation and far less than the 10–20 mSv from an abdominal CT scan. This dose is considered negligible in relation to the potential benefit of early cancer detection. The main risks of screening mammography are false positives (recall for additional imaging that ultimately shows no cancer — about 10% of first-time screens), leading to unnecessary anxiety and further tests, and overdiagnosis — detection of indolent, slow-growing cancers that may never progress to cause symptoms or death in the patient's lifetime. Mammography is significantly less sensitive in women with dense breast tissue (40–50% of women), as both dense tissue and tumours appear white on the image. Supplemental ultrasound or contrast-enhanced breast MRI may be recommended in these women. Mammography cannot detect all breast cancers, and self-examination and clinical examination remain important.