All of the tests carried out at a Dublin hospital to detect a cancerous gene are to be reviewed.
It comes after a woman was mistakenly given the all clear.
In 2009, the woman, who does not want to be identified, got the BRCA1 test because she wanted to rule out the risk of cancer for both herself and her family.
She was given the all the clear by Crumlin's Children Hospital, but last month, her doctors were informed that she had actually tested positive for the breast cancer gene.
The woman is now being treated for an aggressive form of ovarian cancer.
The woman says she "was denied the opportunity for intervention and preventative treatment for almost 10 years" and this has left her in "grave situation."
In a statement this afternoon, Crumlin's Children Hospital apologised to the woman and says it regrets this error and the series of events that led to her current situation.
It will now carry out a review of all BRCA tests as a precautionary measure but is treating this case as an isolated incident caused by human error.
In 2014, the standards in the hospital's genetics department were previously criticised in a report by independent experts.
