Dr. Barbara Heartwell became the subject of several investigations after it was revealed she mistakenly removed the healthy breasts of two women at Hotel-Dieu Grace Hospital.
The College of Physicians and Surgeons investigated Heartwell and decided in May 2011 to caution her, but not refer her to the college's disciplinary committee.
Laurie Johnston had a mastectomy performed by Heartwell, who admitted she misread the results of a needle biopsy that found Johnston did not have cancer, and she appealed the college's decision to another regulatory body.
The Health Professions Appeal and Review Board in May ordered the college to reconsider its decision since it did not appear that previous complaints against Heartwell were considered.
The college has now completed its reconsideration and has once again decided not to discipline Heartwell.
Outcomes of investigations against doctors in Ontario are not publicly released unless the case is referred to the discipline committee.
In cases such as Heartwell's in which the doctor is not sent to the discipline panel, they may have been cautioned or ordered to participate in an educational program, or no action may have been taken.
A provincial report into pathology errors largely cleared Heartwell, but uncovered "significant concerns" with pathologist Dr. Olive Williams' work.
After reviewing more than 6,000 reports stretching back to 2003, investigators had moderate or major disagreements with the original diagnosis in 221 of the cases by Williams.
Hotel-Dieu Grace Hospital has restored full privileges to Heartwell. The hospital suspended Williams and she has since resigned.