Imagine being told you have breast cancer, then undergoing a double mastectomy to remove both breasts. And then, you find out there was no cancer after all.

A Manitoba patient underwent a double mastectomy last year, only to later find out there was no cancer after all. This did happen to someone in Manitoba last year and is reported in Manitoba Health's latest report on critical incidents in the province's health care system.

"Patient underwent unnecessary bilateral mastectomy. An amended radiological report indicating that there was no cancer present did not reach the surgeon," the 2014 report said.

The patient's identity is protected by privacy laws, but a Winnipeg breast cancer survivor Tara Torchia-Wells said she can't imagine what that person must have gone through.

"I can't even wrap my head around it," Torchia-Wells said. "How did it happen?"

To date, Manitoba Health won't say how it happened or what is being done to prevent it from happening again.

"We are unable to speak to specific critical incidents, as some parts of the investigation process are confidential and privileged under law," a provincial spokesperson said in a statement.

"Work is currently underway on implementing the recommendations of the investigation," the spokesperson said, without specifying what those changes are.

'Devastating on top of devastating'

Torchia-Wells said when someone goes through a breast cancer diagnosis and then surgery, "all of those things cause such great pain and anxiety and uncertainty."

Chris Power, CEO of the Canadian Patient Safety Institute says "it's important for us to report these incidents wherever they happen in Canada so that we can each learn from them and prevent them from happening again." (CBC) "But then to find out that you didn't have cancer, and to have already had a bilateral mastectomy would be devastating on top of devastating. I don't understand it. I don't know what a woman would do after that has happened to her."

Once a doctor suspects a patient has cancer, there typically follows a combination of tests such as tissue biopsy, mammogram, ultrasound, or a breast MRI.

There's no way of knowing how often an unnecessary mastectomy happens in Canada because there's no national tracking of such critical incidents, said Chris Power, CEO of the Canadian Patient Safety Institute (CPSI).

She said it has happened though, including one 2013 incident in Nova Scotia while she was head of the Capital Health region in Halifax.

"That's why it's so important for us to be reporting these incidents wherever they happen in Canada so that we can each learn from them and prevent them from happening again."

Halifax case prompts changes

In the Halifax case, the pathology results from two patient tissue samples were switched in the patients' charts.

One patient had a breast removed when the process was unnecessary and the other patient, who needed surgery, was not scheduled for the procedure until after the mistake was caught.

Capital Health explained what happened, publicly apologized for the errors and implemented a barcode system to better track lab specimens.

"We don't see a lot of provinces stepping up and very openly and transparently having those conversations but I think you're going to start to see a change in that because the public is starting to demand it, as they should," Power said.

Power said fear of blame and litigation often makes it hard for healthcare staff to come forward with information about errors.

Manitoba made reporting of critical incidents mandatory in 2006, not to lay blame on individuals but as a way of improving the health care system and reducing the chances of errors being repeated.

Just last month, the province launched the Manitoba Patient Safety Framework, a new five-year plan to improve patient safety, with goals that include "enhancing transparency and accountability, developing trust and open communications between health-care providers, patients and the public, and public reporting of cases, performance and trends."

'People dying preventable deaths'

The Manitoba unnecessary mastectomy case raises questions about why a second radiology report was done and why that amended report didn't get to the surgeon, said Dr. Rob Robson, an Ontario physician who advises on patient safety.

"I feel very, very badly for this lady," said Donna Davis, a Saskatchewan patient safety advocate who was a cancer patient herself. "Obviously this is going to change her life. I just hope there are lessons learned from it." (Jeremy Nielson) "When something has broken down, you could ask this: How is it possible there was a delay in the second report? How is it possible the first report was wrong? How is it possible that the procedures in your operating room didn't pick this up and prevent this?"

He said Manitoba does deserve credit for making the incident public through its website.

But Robson, who previously served as Winnipeg's chief patient safety officer, added that provinces aren't doing enough to study health care errors, which too often are not reported by staff.

"I feel very, very badly for this lady," said Donna Davis, a Saskatchewan patient safety advocate who was a cancer patient herself.

"Obviously this is going to change her life. I just hope there are lessons learned from it."

"I strongly believe in transparency and honesty because that's how we learn," said Davis, whose son died after a medical error in 2002. She said she thinks there's been some improvement since then.

"Are we where we need to be yet? Absolutely not. Because there's still people dying preventable deaths."

"The system is made up of humans and humans are not infallible," Davis said.

"So errors are going to happen. It's indisputable that they're going to happen. It's the response to those errors that makes all the difference in the world."

To contact the CBC I-Team about this story email iteam@cbc.ca or call the confidential tip line at 204-788-3744.