The Waitematā District Health Board has been asked to apologise after failing to identify a woman's red-flag symptoms despite her history with breast cancer.
A report from the Health and Disability Commissioner found the DHB breached its obligations under the Code of Health and Disability Services Consumers' Rights.
The woman started to experience chest pain years after receiving treatment including a mastectomy and radiation therapy.
She visited the public hospital's emergency department with severe chest pain and shortness of breath in February 2018.
Staff at the hospital considered her pain was the result of recent breast reconstruction.
The woman requested a CT scan as she was concerned about a recurrence of her breast cancer, but the scan was cancelled when the Radiology Department did not hear back from the medicine team.
The woman got a scan privately, which showed cancer in her breast and sternum.
In the report, Commissioner Anthony Hill said staff missed opportunities to identify and act upon clinical 'red flag' symptoms when she first arrived at the ED and during her first few days of admission.
"Her history included shortness of breath and chest pain that radiated down her left arm. She said that she had been experiencing chest pain for three and a half months, and that it had become worse following a fall eight days previously, and that she had been experiencing SOB [shortness of breath] and a burning feeling in the central chest region for one month prior to admission," he said.
Hill considered the woman has been let down by various aspects of the care provided to her by numerous DHB staff, the report found.
"It was only through [the woman's] own ongoing significant self-advocacy and ability to arrange a privately performed CT scan that ultimately her correct diagnosis of metastatic breast cancer was reached.
"Because the system for requesting and cancelling CT scans was not sufficiently robust, I find that Waitematā DHB did not provide [the woman] with services with reasonable care and skill."
He recommended that the DHB apologise to the woman in writing, improve communication between departments, and provide additional staff training.