A dental professor failed to diagnose a tumour despite it existing in a pre-cancerous form for 15 years, a hearing has been told.
Professor Philip Lamey is accused of failing to spot the changes in a patient's long-standing condition who had suffered for years with a dry and itchy mouth and eventually turned into cancer.
He also diagnosed smoker's keratosis, damage caused by cigarettes, despite the man not being a smoker and then failed to carry out the right examination to identify any malignant changes in the lesion.
The allegations were made to the General Dental Council at a hearing in London yesterday where dental expert Professor Lamey faces 46 charges of misconduct.
One hundred and thirty-five of his patients at the School of Dentistry at the Royal Victoria Hospital in Belfast had to be recalled after 35 of his patients developed cancer – four of whom died.
The panel heard how one patient, a non-smoker who had suffered from a complaint since the mid-90s, was eventually diagnosed with cancer.
Professor Lamey missed its transformation into a tumour and failed to carry out a biopsy on the lesion.
According to the GDC he also incorrectly recorded that the patient's iron levels were low and prescribed an iron supplement.
Expert witness Professor Stephen Challacombe explained that over a 10-year period there is a 5% risk that oral lichen planus, a common condition, can turn into cancer.
David Bradly, counsel for the GDC, asked: "If there's been something going on there for this amount of time there must come a time that you do need to know what's going on?
Professor Challacombe replied: "It's always important to know what's going on if there's been no significant change.
"The longevity of leukopenia in the oral cavity can last 30 years.
"I would be looking very closely at the keratosis and biopsy would be used for any changes in that lesion."
The patient first reported the symptoms in 1994, followed by visits to Professor Lamey in 2004 and 2009.
Lichen planus can affect people for long periods, although the patient's symptoms flared in 2004.
Mr Bradly asked about the significance of the symptoms being exacerbated so long after the initial diagnosis.
Professor Challacombe said he "would like to know what's going on histologically" – with the cells in the lesion.
When asked by Mr Brady: "You would have biopsied this patient in 2009?" he replied, "Yes".
Earlier the panel heard how a 46-year-old woman, known as patient 33, who had been smoking for 30 years was not given a biopsy despite having smoker's keratosis.
It hid a more serious condition below it, which could have been picked up in a biopsy.
Mr Bradly asked: "If there had been something there previously you would have expected to find it?" Professor Challacombe said: "Yes".
The hearing continues.