A number of patients treated at Our Lady of Lourdes Hospital in Drogheda are being told this week about the miscategorisation of pre-cancerous cells.
The move follows a review of work carried out by one consultant at the hospital in Co Louth across various specialities.
The independent review, which is still ongoing, relates to the period between February and November 2024.
All histopathology slides examined by the consultant during this time will be reviewed.
Histopathology relates to tissues taken during a biopsy, or other surgical specimens, used to diagnose diseases, including cancer.
As a result of the review, some patients are to be advised that the grading of their pre-cancerous cells has been re-classed.
The grading of a person's pre-cancerous cells will determine how closely the cells and the patient are monitored by the HSE.
As a result, some patients, who have had their pre-cancerous cells upgraded on foot of the review, will be called back for further consultation.
However, other patients have also had their pre-cancerous cells downgraded from mild to moderate.
It is understood that a small number of patients have been invited to meetings with the hospital this week in line with the HSE's open disclosure procedures and recent legislation requiring open disclosure.
However, health sources have stressed the cases at issue so far relate to pre-cancerous and not cancerous cells.
They add that no misdiagnoses have so far been identified.
The review is still ongoing and the HSE said it is possible other patients may be invited to similar open disclosure meetings in the future.
In a statement, a spokesperson for Our Lady of Lourdes Hospital said: "In the course of our quality assurance process in the hospital, we commissioned an independent lookback of all histopathology slides across various specialities in relation to one consultant, focusing on a period from February to November 2024.
"This review is under way and any patients in relation to whom any findings are relevant will be contacted directly by the hospital.
"HSE Dublin and North East has provided necessary information to the HSE in line with the National Patient Safety Briefing Protocol."
Meanwhile, Minister for Health Jennifer Carroll MacNeill said she is aware that the "lookback review" is under way.
The minster also said: "The priority is that any affected patients receive the care and treatment they require and that information from the review is provided to them in a transparent and compassionate manner.
"The HSE have advised that this lookback review of histopathology slides relates to the work of one consultant during 2024 and that the review involves histopathology slides across a range of clinical specialities.
"The HSE will continue to update the Department of Health in line with usual protocols.
"I am conscious that the lookback review is not yet completed, so I cannot comment further at this point."
