A doctor in New Zealand has been criticised for forgetting to tell a patient that she probably had metastatic breast cancer.

A doctor has been ordered to apologise to the family of a New Zealand woman who died after he "completely forgot" to tell her she had breast cancer.

The woman died earlier this year after a five-year battle with breast cancer which her GP failed to diagnose quickly, despite being told by a specialist that she probably had the disease.

In a scathing report released by New Zealand's Health and Disability Commissioner Anthony Hill on Monday, the GP was told to review his practice and audit his clinical files to ensure he didn't miss more cancer cases involving other patients.

The woman, who had breast cancer treatment in 2003, went to the unidentified medical centre in November 2009 complaining of pain in her left shoulder.

The doctor, who was aware she was a cancer survivor, referred her for an x-ray which a specialist radiologist said revealed a tendon tear that appeared "highly suggestive of metastasis", or the spread of cancerous lesions.

The GP saw the woman again several days later but failed to tell her about the cancer link, instead only informing her of the tendon tear and giving her a steroid injection which the woman said was "excruciating".

She was told to return in a month if the pain persisted, which she did once in December and again in January before the doctor finally referred her to an orthopaedic surgeon.

The woman was diagnosed in February 2010, after which she changed doctors. Despite several years of active treatment, the woman died.

The doctor told the inquiry he "either overlooked or completely forgot about the radiologist's comment in relation to a suspicious lesion", the report states.

Mr Hill criticised the GP for failing to read his own notes, ask the right questions, or reflect on his patient's medical history when assessing her.

"Doctors owe patients a duty of care in handling patient test results, including advising patients of, and following up on, results," he said.

The GP has been referred to the Director of Proceedings for possible legal action.

Copyright AAP 2014