Last reviewed: February 2026 by the thrive.md Clinical Advisory Team
What is a Mammogram?
A mammogram is a low-dose X-ray image of the breast. It's the most effective screening tool for detecting breast cancer early—often 2-3 years before a tumor can be felt as a lump. There are two types:
Screening mammograms are routine exams for women without breast symptoms. They typically include two X-ray images of each breast and take about 20 minutes.
Diagnostic mammograms are performed when there's a symptom (lump, pain, nipple discharge) or an abnormal screening result. They involve additional views and often take longer.
During the exam, your breast is placed on a platform and gently compressed by a clear plastic paddle. The compression spreads the breast tissue evenly, allowing for clearer images with less radiation exposure. While uncomfortable, it lasts only a few seconds per image.
When Should You Get a Mammogram?
Screening recommendations vary by organization. Here's a comparison of major guidelines for women at average risk (no genetic mutations, family history, or prior breast cancer):
| Organization | Start Age | Frequency | Stop Age |
|---|---|---|---|
| USPSTF (2024) | 40 | Every 2 years | 74 (insufficient evidence for 75+) |
| American Cancer Society | 45 (option at 40-44) | Yearly at 45-54; every 2 years at 55+ | Continue if life expectancy ≥10 years |
| ACR / SBI | 40 | Yearly | Continue as long as healthy |
| ACOG | 40 (no later than 50) | Every 1-2 years | 75+ based on health status |
Note: USPSTF = U.S. Preventive Services Task Force; ACR = American College of Radiology; SBI = Society of Breast Imaging; ACOG = American College of Obstetricians and Gynecologists.
💡 Higher Risk? Start Earlier
Women with a family history of breast cancer, BRCA1/BRCA2 mutations, history of chest radiation, or other risk factors may need to start screening earlier (sometimes in their 20s or 30s) and may benefit from MRI in addition to mammography. Talk to your doctor about your personal risk.
What Happens During a Mammogram?
Understanding what to expect can help reduce anxiety. Here's a step-by-step overview:
Before the exam:
- Schedule 1-2 weeks after your period when breasts are less tender
- Don't wear deodorant, antiperspirant, powder, or lotion on your chest/underarms (can appear as spots on images)
- Wear a two-piece outfit for easy undressing from the waist up
- Bring prior mammogram images if you're going to a new facility
During the exam:
- You'll undress from the waist up and wear a gown
- A technologist positions your breast on the X-ray platform
- A plastic paddle compresses your breast firmly (uncomfortable but brief—a few seconds)
- Two views are taken of each breast: from above and from the side
- The entire process typically takes 15-30 minutes
After the exam:
- You can resume normal activities immediately
- Results are usually available within 1-2 weeks
- You'll receive a written summary of your results and breast density
What Are Dense Breasts and Why Do They Matter?
Breast density refers to the amount of fibrous and glandular tissue compared to fatty tissue in your breasts. There are four categories:
| Category | Description | Prevalence |
|---|---|---|
| A: Almost entirely fatty | Breasts are almost all fat | ~10% |
| B: Scattered fibroglandular | Some dense areas within fatty tissue | ~40% |
| C: Heterogeneously dense | Much of the breast is dense (may hide small masses) | ~40% |
| D: Extremely dense | Almost entirely dense tissue | ~10% |
Why density matters:
- Dense tissue appears white on mammograms—so do tumors. This can mask cancers.
- Women with dense breasts (categories C & D) have a 4-6x higher risk of breast cancer.
- Mammograms are less sensitive in dense breasts (may miss 30-40% of cancers).
- Additional screening (ultrasound, MRI) may be recommended.
The FDA now requires that all mammography facilities inform women about their breast density. If you have dense breasts, discuss supplemental screening options with your doctor.
3D Mammography vs. 2D: What's the Difference?
2D digital mammography captures flat images of the breast from two angles. It has been the standard for decades and is highly effective.
3D mammography (digital breast tomosynthesis or DBT) takes multiple X-ray images at different angles and creates a three-dimensional view of the breast. Think of it like a CT scan for the breast.
| Factor | 2D Mammography | 3D Mammography (Tomosynthesis) |
|---|---|---|
| Cancer detection | Standard | 20-65% more cancers detected |
| False positives (callbacks) | Higher | 15-40% fewer callbacks |
| Dense breast performance | Good | Better (sees through overlapping tissue) |
| Radiation dose | Lower | Slightly higher (still within safe limits) |
| Insurance coverage | Widely covered | Most plans cover; some charge extra copay |
The American College of Radiology recommends 3D mammography as the preferred screening method when available, especially for women with dense breasts.
Understanding Your Mammogram Results
Mammogram results are reported using the BI-RADS (Breast Imaging Reporting and Data System) scale:
| BI-RADS | Assessment | What It Means | Next Steps |
|---|---|---|---|
| 0 | Incomplete | Need additional imaging | Additional mammogram views or ultrasound |
| 1 | Negative | No abnormalities found | Routine screening |
| 2 | Benign | Non-cancerous finding (cyst, calcification) | Routine screening |
| 3 | Probably benign | <2% chance of cancer | Short-term follow-up (6 months) |
| 4 | Suspicious | 2-95% chance of cancer | Biopsy recommended |
| 5 | Highly suggestive | >95% chance of cancer | Biopsy required |
| 6 | Known cancer | Biopsy-proven malignancy | Treatment planning |
⚠️ Getting Called Back? Don't Panic
About 10-12% of women are called back after a screening mammogram for additional imaging. Of those called back, fewer than 10% are diagnosed with cancer. Most callbacks result in a finding that's benign or just need clearer images. While waiting is stressful, try not to assume the worst.
Making Informed Decisions About Screening
Mammography screening has clear benefits but also limitations. Understanding both helps you make informed decisions with your healthcare provider:
Benefits:
- Early detection when cancer is most treatable (99% 5-year survival for localized breast cancer)
- Can detect cancers 2-3 years before they can be felt
- Reduces breast cancer deaths by 20-40% in screened populations
- May allow for less aggressive treatment when caught early
Limitations:
- False positives: About 50% of women screened annually for 10 years will have at least one false-positive result
- Overdiagnosis: Some detected cancers may never cause symptoms or harm (estimated 1-10%)
- False negatives: Mammograms miss about 15-20% of breast cancers (more in dense breasts)
- Radiation exposure: Very low dose, but repeated over many years
This is not medical advice. Discuss your personal risk factors, family history, and screening preferences with your healthcare provider to create a plan that's right for you.