Onsite Mammography Data Breach Affects PHI of 357,265 Americans: SSNs Exposed

On October 4, 2024, Onsite Mammography discovered unusual activity in one of its employee’s email accounts, which led to the identification of a data breach involving protected health information (PHI) of 357,265 individuals according to a disclosure to the Maine Attorney General's office on April 21, 2025.

According to the official press release from Onsite Mammography, an unauthorized actor gained access to this single email account that contained health-related information about patients, which are classified as protected health information (PHI).

The disclosure to the Texas Attorney General's office on April 22nd added that social security numbers and dates of birth were also exposed in the incident.

Onsite Mammography's response

In response to the breach, Onsite Mammography took several actions to protect affected individuals and prevent similar incidents in the future. The company immediately engaged outside cybersecurity professionals to investigate and contain the incident.

Additionally, Onsite brought in a data analytics vendor to conduct a thorough review of the impacted files and determine the extent of the PHI involved.

Onsite has since implemented additional security measures to further minimize the risk of similar incidents. The company also notified law enforcement and is actively reviewing its data protection policies and procedures.

For those who may have been affected, Onsite recommends remaining vigilant for signs of identity theft or fraud. This includes carefully reviewing credit reports, account statements, and explanation of benefits forms for any suspicious activity or errors. Individuals can also place a fraud alert or credit freeze by contacting the major credit reporting agencies: TransUnion (1-800-680-7289), Experian (1-888-397-3742), and Equifax (1-888-298-0045).

To learn more about protecting your information and steps to take if you suspect identity theft, you can visit the Federal Trade Commission’s identity theft resource page.

For more information about the company and its services, visit Onsite Mammography’s official website.