Marin Cancer Care

Marin Cancer Care notified the California Attorney General of an unauthorized access incident. The organization learned of the breach on December 8, 2025, after investigators identified unauthorized network access between November 22, 2025, and December 6, 2025. Files were copied from the network. Affected data may include names, addresses, phone numbers, email addresses, Social Security numbers, dates of birth, medical record numbers, diagnoses, treatments, and health insurance information. The company engaged third-party investigators, reviewed affected files, and is providing complimentary identity monitoring to affected individuals. No ransomware or specific threat actor was identified.