A review of patient medical information found that 38 people who weren't previously identified need to have their breast cancer treatment tests retested, Eastern Health said in a statement late Friday.
It wasn't known whether their tests were botched.
"This is what the testing should determine," said Eastern Health spokeswoman Deborah Collins.
Eastern Health said 24 of those 38 patients are dead, though it wasn't immediately clear how they died.
"We apologize for the distress this late identification may cause our patients," Eastern Health said in its statement.
"However, we also take some measure of reassurance that this enhanced review process by (the Newfoundland and Labrador Centre for Health Information) has accomplished what it was designed to do."
Eastern Health became the subject of an inquiry that found a litany of problems led to at least 386 breast cancer patients receiving the wrong results on tests intended to determine an appropriate course of treatment.
At least 108 patients whose tests were misread have died. But it will likely never be known how many of them, if any, died as a result of missing out on potentially life-saving treatment.
The inquiry heard that the St. John's laboratory that processed the tests was overwhelmed by staff shortages, improper training and a lack of internal controls.
Witnesses also testified there was infighting among medical staff, communication lapses between the Newfoundland government and Eastern Health, and failed attempts at damage control.
Justice Margaret Cameron concluded that a failure of accountability and oversight "at all levels" within Newfoundland and Labrador's health-care system led to the mistakes.
"The whole of the health system, to varying degrees, can be said to have failed the ... patients," Cameron wrote in her 495-page report, released early last month.
Peter Dawe of the Canadian Cancer Society said he was taken aback by the number of additional patients whose tests need to be reviewed.
"That number kind of jumps out at you," Dawe said.
"It represents 38 people and 38 families who have to go through this process again."
Dawe also said he found it ironic that Eastern Health would release this information in a statement late Friday after the heavy criticism it received for the state of its public communications.
"It just feels like they were reverting back to what they were doing in 2005," he said.
In November, Eastern Health enlisted the help of the Newfoundland and Labrador Centre for Health Information to identify any remaining patients whose breast cancer tests were missed in a review of tests conducted from 1997 to 2005.
"In accordance with the guidelines for patient disclosure, Eastern Health is in the process of contacting the living patients and their physicians to inform them of the results of this enhanced search process, and to discuss their follow-up care," Eastern Health's statement said.
Eastern Health said it was aware of four living patients who may require a change in treatment, an indication that their original tests may have been misread.
Problems with the testing were detected in the spring of 2005, when doctors began questioning the hormone receptor test results of a patient with invasive lobular carcinoma, a form of breast cancer.
After retesting, it was discovered that the initial test result was wrong, as were those for a small sample of other patients.
Eastern Health subsequently halted testing in its St. John's lab and transferred its hormone receptor tests to Mount Sinai Hospital in Toronto.
The health board then started a review of all hormone receptor tests from 1997 to 2005.
The latest retesting process, to be conducted at an external laboratory, is expected to take at least four weeks, Eastern Health said.
The province is not currently conducting hormone receptor testing, but Eastern Health hopes to resume the service in the near future.
After the tests, if patients are found to be estrogen- and/or progesterone-positive, they may respond to hormone therapy such as Tamoxifen. If not, they may be given a range of other treatments, or no treatment at all, depending on the characteristics of the patient's cancer.
Patients whose breast cancer tests dated back to 1997 say they first became aware there might be problems with the tests when a local weekly newspaper reported in October 2005 that a small number of them generated questionable results.
For up to two years, patients and their relatives complained Eastern Health wasn't notifying them of reviewed test results.
