# Mammography Quality Standards Act (MQSA) and the breast density notice

Source: https://onco.cc/terms/mqsa-breast-density-notice/  
OnCo record `mqsa-breast-density-notice` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A US federal law sets quality standards for mammography facilities. Its rules require each woman's results letter to say in plain words whether her breast tissue is dense, because dense tissue makes cancer harder to see on a mammogram and raises the risk of breast cancer.

## Summary

United States, the Mammography Quality Standards Act (42 U.S.C. 263b), implemented by FDA regulations in 21 CFR part 900, which set the standards a facility must meet to perform screening or diagnostic mammography and the system of accreditation bodies that check them.

Under 21 CFR 900.12(c), each mammography report must give an overall assessment of breast density in one of four categories, from "The breasts are almost entirely fatty" to "The breasts are extremely dense, which lowers the sensitivity of mammography". The facility must send the patient a lay summary within 30 calendar days. Where the tissue is heterogeneously or extremely dense, the summary must say: "Breast tissue can be either dense or not dense. Dense tissue makes it harder to find breast cancer on a mammogram and also raises the risk of developing breast cancer. Your breast tissue is dense. In some people with dense tissue, other imaging tests in addition to a mammogram may help find cancers. Talk to your healthcare provider about breast density, risks for breast cancer, and your individual situation." Where it is not dense, a matching statement says so.

## Fields

- Kind: Term
- Last checked: 2026-11-04
- Also known as: MQSA; Mammography Quality Standards Act; 42 U.S.C. 263b; 21 CFR 900; breast density notification; dense breast notification
- Tags: law; us

## Notes

- Read from the eCFR versioner API (text current to 1 October 2026). The date the density notice took effect and the Act's year of enactment were not stated in the text read and are left out.

## Sources

- eCFR: 21 CFR 900.12, quality standards (current text): https://www.ecfr.gov/current/title-21/chapter-I/subchapter-I/part-900/subpart-B/section-900.12
- eCFR: 21 CFR part 900, mammography: https://www.ecfr.gov/current/title-21/chapter-I/subchapter-I/part-900

## Connected records

- technologies: [Mammography & tomosynthesis](https://onco.cc/technologies/mammography/)
- institutions: [FDA Oncology Center of Excellence](https://onco.cc/institutions/fda-oce/)

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JSON: https://onco.cc/api/v1/entities/mqsa-breast-density-notice.json