Dr. Nash Denic says he believes that equipment failure was a factor in explaining how hundreds of breast cancer tests went wrong. (CBC)

A pathologist has told Newfoundland and Labrador's breast cancer inquiry that he still believes equipment played a role in faulty tests, even though external reviews pointed to human error.

Dr. Nash Denic, chief of pathology at Eastern Health, told the Cameron inquiry that he is not convinced equipment failure could be ruled out to explain how hundreds of hormone receptor tests yielded wrong results.

Two external reviewers in 2005 found ruled out a change in equipment, and pointed instead to other problems, including faulty preparation, woefully inadequate training and high staff turnover.

"I don't think it's a single factor.… There are multiple factors involved," Denic told the inquiry on Friday. "I still believe that that piece of equipment could have had certain failure."

For its hormone receptor tests, Eastern Health switched four years ago from one system, known as DAKO, to a more sophisticated Ventana system.

Denic added he was referring not to the DAKO system itself, but the specific machine involved in the tests.

Even though the 2005 reviews — which were not made public until earlier this year, on the eve of the Cameron inquiry's launch — highlighted operating problems, Eastern Health officials had consistently pointed to equipment failure as a probable cause when explaining the issue to government and to the public.

Eastern Health's chair, Joan Dawe, testified at the inquiry this spring that she was led to believe equipment failure was the likely cause as lately as this year.

Denic told the inquiry he believes there are still reasons to consider that equipment failure was involved. He reviewed some of retested samples that were returned with changed results, and determined that not all of the tests involved badly prepared tissue samples.

He said that could only mean one thing. "The machine itself gives a problem — a random problem," he testified.

To verify his suspicions, he contacted another jurisdiction and confirmed that their lab also had problems with the same kind of machine. Denic compares it to a traffic accident where investigators first look to see if there were mechanical problems.

"I've been a forensic pathologist for years and working on traffic investigators," Denic said. "When a traffic accident occurs, investigators want to examine the vehicle first and unfortunately, that piece of [equipment] wasn't there, and I really don't know where it is.…

"I think it could have played the role in certain number of cases. I'm not saying that all cases are related to that," he said.

There is no way of knowing whether the machinery formerly used at Eastern Health was faulty. It was removed from the lab in 2004.

Since March, Cameron has been hearing evidence on what went wrong in the St. John's pathology lab, and on how officials dealt with the problem from 2005 onward.

The hormone receptor tests are used to help determine whether a breast cancer patient can benefit from antihormonal therapy, usually involving the drug Tamoxifen.