A major review of breast-cancer services in north-east England has found that 20 women underwent unnecessary mastectomies during treatment at County Durham and Darlington NHS Foundation Trust.

The internal review examined more than 300 patient cases, with 77 identified as involving significant harm. The cases include concerns around missed or misdiagnosed cancers and treatment decisions. One patient has died, according to reports.

The findings have prompted further scrutiny of the trust's breast-care services. Durham Police and the National Crime Agency are investigating, while the trust has said changes have been made to improve the service and expressed regret over the harm identified.

The case highlights the importance of accurate cancer diagnosis, specialist review and patient safety within NHS breast-care services.

A trust board meeting is expected to consider the continuing review, while affected patients have access to a dedicated support service.

The developments are likely to increase attention on NHS cancer care standards, clinical governance and patient safety, particularly as health authorities examine how the failures occurred and what further action may be required.