A helpline has been set up for anyone who is concerned that they may have had their pre-cancerous cells mis-categorised at Our Lady of Lourdes Hospital in Drogheda.
It comes as a review of the work carried out by one consultant at the hospital in Co Louth, is under way.
All histopathology slides examined by the consultant across various specialities between February and November of last year are being reviewed.
Histopathology relates to tissues taken during a biopsy, or other surgical specimens, used to diagnose diseases, including cancer.
A spokesperson for Our Lady of Lourdes Hospital has confirmed that just over 1,000 patients are to have their histopathology results reviewed, with the review now about halfway to completion.
Of these, four patients are being invited to open disclosure meetings with the hospital, at which it will be explained that their biopsy results are not as originally communicated to them.
The review has so far found that two patients had a 12-day delay in their treatment plans.
The hospital has also said that in the case of one patient, there was an additional biopsy performed which was not necessary.
Two other cases identified relate to the categorisation of pre-cancerous cells.
The categorisation (or grading) of a person's pre-cancerous cells determines how closely the cells and the patient are monitored by the HSE.
Some patients, who have had their pre-cancerous cells upgraded on foot of this review, will be called back for further consultation.
However, other patients have also had their pre-cancerous cells downgraded.
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.
In a statement, a spokesperson for Our Lady of Lourdes Hospital confirmed they will also be communicating with "several dozen" patients in cases where no additional action will be required.
The spokesperson said: "We will also be writing to several dozen patients to explain a variance between their original test result and the view of the independent reviewers. In none of these cases is there any change in their management required.
"All doctors go through a robust recruitment and onboarding process."
A helpline for anyone concerned that they may be affected by the review can be contacted by phoning 1800 66 77 00.
The helpline will be available from 9am-6pm Monday to Friday and from 9am-2pm Saturday and Sunday this weekend.
