One patient had an unnecessary mastectomy and another had a necessary surgery delayed at a Halifax-area hospital after their test results were switched with two other patients.

The Capital District Health Authority said Monday it made mistakes in two separate instances, both involving cancer patients.

The Halifax-area health authority said in one case the tissue samples after a pathology test were switched on 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.

The woman in her 60s who had the unnecessary mastectomy is being represented by lawyer Ray Wagner. Wagner said his client, who is from the Halifax region, had her surgery on March 28 but wasn't notified of the error until May 17, when her family doctor told her about the mix-up.

"She accepted the fact of the diagnosis of the cancer, accepted the treatment which is radical treatment and then to be advised afterwards that you never did have it," said Wagner.

"Now you're short a breast as a result of the mastectomy and now you have the anger and the emotion and the upset of having a radical procedure performed on you that wasn't necessary."

Nova Scotia Health Minister Dave Wilson said he felt sick upon hearing the news about the mix-ups.

"To be quite truthful, I felt quite ill when I learned about these two events that took place and I feel terrible for all the patients who were involved in these two events," he said.

"One of the things we want to make sure is that when Nova Scotians get access to health-care services, they can get that and receive that in a safe environment."

Chris Power, the president and CEO of the Capital District Health Authority, said the hospital acted on the mistake as soon as it was discovered during the quality control process.

"An initial biopsy is usually taken for people and then it's determined [whether] they have cancer and then surgery is scheduled. So at that point in time there is an analysis of tissue.… Once the surgery takes place, another biopsy or tissue sample is taken and then that goes to the lab and once that's read, we compare the two to be sure," said Power.

She said there was a discrepancy in the tissue samples and authorities realized they did not belong to the same patient.

Samples switched in 2nd, separate case

In a second, separate case, tissue samples were switched before the pathology analysis. One patient had an unnecessary diagnostic biopsy and the other patient never got the followup they needed.

The Capital District Health Authority is releasing few details about the patients or when the mix-ups happened.

"To those patients directly affected by this event, we give our most sincere apology," Capital Health said in an emailed statement.

It said it uncovered the mix-up using "quality assurance mechanisms." All tissue samples removed during surgery are reviewed.

"The two cases didn't happen at the same time but for the first case that has come to light for us, the tissue was examined and one patient's report went on another patient's chart and vice versa, so they were transposed," said Power.

"In the second incident, when the actual tissue was being prepared to go to be read, there was a change in the name so the wrong labelling was put on."

Chris Power is the CEO and president of the Capital District Health Authority. (CBC)

Power said the hospital has since reviewed other tissue removed during the same time.

"[We are] very confident that these are isolated cases. Not to our knowledge have they happened before in Nova Scotia. They've certainly happened in other places around the world, lots of times and across Canada but not to our knowledge in Nova Scotia, we're very confident," she said.

"I'd just like to say how terribly sorry we are to the people who have been affected by this. These are isolated cases, we want to assure the public that if you've had a biopsy or something at Capital Health, not to worry that you are one of these people because these four people have been notified and we are working with them to get the care and support that they require."

Power said that no one has lost their job because of these incidents. She said that the hospital does everything it can to ensure patient safety and that staff are encouraged to come forward when they suspect a mistake has occurred so that it may be corrected as soon as possible.

"We do the best that we can and have very good processes put in place. But in health care, adverse events happen and we know that it happens and so typically [there is] a combination of systems that are put in place and human error — and that would be the case in these instances."

The health minister echoed Power's sentiments.

"No matter how many policies, how many checks and balances you have in place, no matter how advanced the technology is and the equipment you use — the health-care system is delivered by people and people make mistakes and in these two cases that's what happened and it's our hope that it won't happen in the future," said Wilson.

New protocols to be implemented

Power said, going forward, the health authority will implement a bar coding system for laboratory specimens. Also, she said, there are plans to implement an automated system to reduce the amount of human handling during the laboratory testing process.

She said that she couldn't speak to the specifics of how the patients affected are dealing with this news but she did say that the patients are traumatized.

"This has been a very difficult time for them, as you can well imagine, and this will be a difficult time for them to see it in the media and the press," said Power.

"I can say that it was very traumatic for our patients, as you would expect. If it was you that that had happened to — that you either didn't think that you had cancer and then you found out that you did or vice versa, that you were told you do and now you didn't — anybody would react to that in a very emotional way."