A mammogram is an X-ray of the breast used to detect cancer before a lump can be felt, and to investigate a lump or other breast symptom. Screening mammography targets asymptomatic women; diagnostic mammography targets women with a known symptom or finding. The radiation dose is very low — equivalent to around 7 weeks of background radiation from the environment.
When to start and how often
Screening guidelines vary by country and by individual risk. In most national programmes, routine mammography begins at age 40–50 and is offered every 1–2 years up to age 70–75. Women at higher risk — due to BRCA gene variants, a strong family history, prior chest radiation, or certain benign breast conditions — may be recommended to start earlier and screen more frequently, sometimes with MRI alternating with mammography.
| Risk category | Recommended start age | Frequency |
|---|---|---|
| Average risk | 40–50 (varies by guideline) | Every 1–2 years |
| Elevated risk (e.g. first-degree relative) | 10 years before relative's diagnosis or age 40 | Annually |
| High risk (BRCA1/2, > 20% lifetime risk) | 25–30 | Annual mammogram + MRI |
What to expect at the appointment
Each breast is compressed between two plates while an X-ray is taken — from above and from the side. Compression is brief (a few seconds per image) and may be uncomfortable, particularly around the time of a menstrual period when breast tissue is more sensitive. Scheduling 1–2 weeks after a period reduces discomfort. The whole appointment takes around 20 minutes.
Most modern mammography systems are digital. Some centres offer 3D mammography (tomosynthesis), which takes multiple thin-slice images and reduces false positives, particularly in women with dense breast tissue.
Reading the results: the BI-RADS scale
Results are reported using the standardised BI-RADS (Breast Imaging Reporting and Data System) scale from 0 to 6.
- BI-RADS 0 — Incomplete; additional imaging needed before a final assessment
- BI-RADS 1 — Negative; no significant finding
- BI-RADS 2 — Benign finding; no action needed
- BI-RADS 3 — Probably benign; short-interval follow-up recommended (usually in 6 months)
- BI-RADS 4 — Suspicious; biopsy recommended
- BI-RADS 5 — Highly suggestive of malignancy; biopsy required
- BI-RADS 6 — Known biopsy-proven malignancy; for monitoring
Dense breast tissue
About 40% of women have dense breast tissue. Dense tissue appears white on a mammogram — as does cancer. This means cancers can be hidden in dense tissue, and the mammogram's sensitivity is lower. Many countries now include breast density in the mammogram report, and women with dense breasts may be offered supplemental ultrasound or MRI screening.
"A mammogram invitation is not optional admin. It is a clinically structured opportunity to catch a cancer before it becomes dangerous."
Dr. Lina Haddad, CMO, Looms
Keeping your mammogram records
Always keep copies of your mammogram reports and, if possible, the images themselves. When you attend a new centre, previous images are invaluable — radiologists compare current findings to prior studies to detect subtle change. Uploading mammogram reports to your Looms record ensures they follow you regardless of which clinic you attend.