Mammography & Breast Imaging

What It Shows

• Breast masses — size, margins, density (spiculated = high suspicion for malignancy)
• Microcalcifications — tiny calcium deposits often associated with DCIS (pre-invasive cancer)
• Architectural distortion — subtle structural changes indicative of cancer
• Axillary lymph node enlargement
• Extent of disease pre-surgery — especially invasive lobular cancer (poorly seen on mammography)
• Breast implant integrity
• Response to neoadjuvant chemotherapy — tumour size reduction pre-surgery
• Contralateral breast disease in newly diagnosed patients (MRI detects synchronous cancers in 3–9%)

How It Works

Mammography: Each breast is compressed between two flat plates and two X-ray images are taken (craniocaudal and mediolateral oblique views). Compression reduces radiation dose and improves image quality. Tomosynthesis acquires multiple low-dose images at different angles, reconstructed into 3D slices — improving visualisation through overlapping dense tissue. Breast ultrasound uses high-frequency sound waves; no radiation. Breast MRI uses gadolinium contrast and multiple MRI sequences; requires dedicated breast coils in prone position.

• Annual screening from age 50 (NHS; USPSTF) — or age 40 (ACR, ACS) for average-risk women
• Annual breast MRI from age 25–30 for BRCA1/2 carriers
• Diagnostic mammogram for symptomatic patients (lump, skin change, nipple discharge)
• Pre-surgical planning — disease extent, multifocality, contralateral assessment
• Monitoring response to neoadjuvant chemotherapy
• Surveillance in treated breast cancer patients

Mammographic screening has the strongest evidence of any cancer screening intervention. Meta-analyses of randomised trials show 15–20% reduction in breast cancer mortality in screened women. The UK Age Trial demonstrated benefit for women starting screening at 40. Tomosynthesis (3D mammography) shows 41% improvement in invasive cancer detection and 15% reduction in recall rate (JAMA 2014). Breast MRI in BRCA carriers detects 71–77% of cancers vs 33–40% for mammography alone. Breast MRI sensitivity for invasive breast cancer exceeds 90% but has lower specificity (false positive rate ~30%), making it unsuitable for population screening in average-risk women.

Preparation & What to Expect

Mammography: schedule 1 week after period (breast less tender). Do not use deodorant, powder, or lotion on breasts or underarms. Remove upper clothing and jewellery. Each X-ray takes seconds; brief discomfort from compression. Breast MRI: Remove all metal; IV cannula for gadolinium; prone position in MRI machine for 40–60 minutes.

• Dense breast tissue reduces mammography sensitivity — dense breasts require ultrasound or MRI supplement
• Mammography misses 10–20% of breast cancers (false negatives) — clinical examination remains essential
• Overdiagnosis concern: some screen-detected cancers (especially low-grade DCIS) may never have caused harm
• Breast MRI high false positive rate (30%) — leads to benign biopsies
• Breast MRI not validated for population screening in average-risk women

• Radiation from mammogram is very low (~0.4 mSv) — far outweighed by the benefit of cancer detection
• Gadolinium in breast MRI — same precautions as for any gadolinium-enhanced MRI (kidney function, pregnancy)
• Abnormal mammogram result requires specialist radiologist review — do not interpret alone