Breast cancer screening after 40: US guidelines explained

If you are 40 or older and at average risk, US guidelines now agree that you should start screening mammograms. The US Preventive Services Task Force recommends one every 2 years from 40 to 74; ACOG says every 1 or 2 years; the American Cancer Society favors yearly screening, at least from 45 to 54. The differences are about frequency and the balance of benefits and false alarms, not about whether women in their 40s should be screened.

Why the starting age moved to 40

For years, the USPSTF advised routine screening from 50 and an individual decision in the 40s. Its 2024 update made biennial screening from 40 a grade B recommendation, citing two trends:

• Rising incidence in younger women. Breast cancer rates among women aged 40 to 49 rose gradually from 2000 to 2015, then faster, by an average of 2.0% a year from 2015 to 2019.
• Persistent racial disparities. Black women are about 40% more likely than white women to die of breast cancer (27.6 versus 19.7 deaths per 100,000).

ACOG followed in 2024, changing its guidance from “offer” screening at 40 to recommending that all average-risk women begin screening at 40.

The numbers: benefits and harms

The USPSTF relied on modeling of a lifetime of screening. For every 1,000 women screened every 2 years from 40 to 74 rather than 50 to 74:

Outcome per 1,000 women over a lifetime	Biennial screening, 40 to 74
Additional breast cancer deaths averted vs starting at 50	1.3 (1.8 for Black women)
False-positive results	1,376
Overdiagnosed cancers (would never have caused harm)	14 (range 4 to 37 across models)

A false positive means a callback for more imaging, sometimes a biopsy, that turns out not to be cancer. The models project more false positives than women screened, so many women can expect at least one callback over the years. The National Cancer Institute stresses that most people who are called back do not have breast cancer. The models also found that biennial screening has a more favorable balance of benefits to harms than annual screening, although no randomized trial has compared the two directly.

If you are called back

Mammogram results are reported in BI-RADS categories from 0 to 6. A category 0 means the radiologist needs more images before reaching a conclusion, which is the most common reason for a callback. The next step is usually a diagnostic mammogram, an ultrasound or both. Depending on what they show, you may be told to return to routine screening, come back for a short-interval check, or have a biopsy; categories 4 and 5 point toward a biopsy. Waiting for results is stressful, so ask the facility when and how you will hear, and remember that a callback alone says little about whether you have cancer.

Screening recommendations by age

Age	USPSTF (2024)	American Cancer Society
40 to 44	Mammogram every 2 years	Option to start yearly mammograms
45 to 54	Every 2 years	Yearly
55 to 74	Every 2 years	Every 2 years, or continue yearly
75 and older	Insufficient evidence to recommend for or against	Continue while in good health and expected to live at least 10 more years

ACOG recommends starting at 40 and screening every 1 or 2 years, chosen through shared decision-making with your clinician.

The USPSTF considers both standard digital mammography and digital breast tomosynthesis (3D mammography) effective.

Who these guidelines do not cover

These schedules are for women at average risk. They do not apply if you have a BRCA1 or BRCA2 mutation or another high-risk genetic marker, received high-dose chest radiation at a young age, have had breast cancer, or have had a high-risk breast lesion on biopsy. The American Cancer Society considers women with an estimated lifetime risk of about 20% to 25% or more to be high risk; the ACS recommends a breast MRI and a mammogram every year for them, typically starting at age 30. It recommends against MRI screening for women whose lifetime risk is under 15%.

Ask your clinician to estimate your lifetime risk if you have a strong family history of breast or ovarian cancer.

Dense breasts

Breast density describes how much of the breast is fibrous and glandular tissue rather than fat. The National Cancer Institute reports the four categories used on reports:

Category	Description	Share of women
A	Almost entirely fatty	About 10%
B	Scattered fibroglandular tissue	About 40%
C	Heterogeneously dense	About 40%
D	Extremely dense	About 10%

Categories C and D count as dense. Nearly half of women 40 and older who get mammograms have dense breasts. Dense tissue makes cancers harder to see and is linked to a higher risk of developing breast cancer, although women with breast cancer and dense breasts are no more likely to die of it than those with fatty breasts.

Since September 10, 2024, an FDA rule requires every mammography facility to tell you in plain language whether your tissue is dense or not dense. If it is dense, the notice adds that other imaging tests may help find cancers in some people and advises you to talk with your provider. The USPSTF found insufficient evidence for or against routine supplemental ultrasound or MRI in women with dense breasts and a normal mammogram, so the decision depends on your overall risk.

Where hormone therapy fits

Combined estrogen-plus-progestogen therapy is associated with a small increase in breast cancer risk with longer use, while estrogen alone has a different profile. If you use or are considering hormone therapy, keep up with screening on the same schedule as other women your age and tell the facility you are using it. Our guides to hormone therapy and breast cancer risk and is hormone therapy safe? give the absolute numbers.

When to see a clinician

• You are 40 or older and have not had a screening mammogram.
• You notice a new lump, skin dimpling, nipple changes or discharge, or a persistent change in one breast. These need a diagnostic evaluation, not routine screening, regardless of when your last mammogram was.
• You have a family history of breast, ovarian or related cancers, or a known genetic mutation.
• Your report says your breasts are dense and you want to discuss your risk.

Bring your family history to the appointment; our questions to ask your doctor can help. You can also find an OB-GYN or menopause specialist in our directory.