An Isle of Man hospital has announced an investigation into claims that a series of test results that were issued to patients were inaccurate.
Noble's Hospital in Strang, Douglas, has also revealed that it is taking legal advice from the UK over the matter.
The inaccurate test results were given to more than 20 breast cancer patients, who were subsequently called in for a full treatment review after mistakes were made in hormone tests.
Breast cancer treatment plans are devised based on the susceptibility of the tumour to various types of hormone therapy. The tests identify the most appropriate treatment for the particular type of cancer, giving the patient the best chance of recovery.
Although none of the 20 patients would have been misdiagnosed as a result of the errors, they may well have been placed on a treatment regime that was less appropriate for their particular type of tumour.
Isle of Man Health Minister David Anderson said the matter was being taken very seriously.
"The matter is being treated with the utmost urgency," he said in a statement.
"The department has notified all the patients affected and arrangements have been made for these women to be seen as soon as possible- so far, all but two have been seen," he added.
The hospital is continuing to investigate why the results were wrong and believes that the number of patients affected by the mistakes could rise in time to more than 40.
It is feared that the mistakes could give rise to legal action for medical negligence, although there has been no suggestion yet that any of the patients are considering compensation claims.