Potentially malignant oral lesions in Northern Ireland: size (extent) matters.

OBJECTIVES: We examined clinical parameters of patients from Northern Ireland with potentially malignant lesions (PML) to determine association with development of intraoral squamous cell carcinoma (SCC). DESIGN: retrospective, cross-sectional, population-based, clinically validated, laboratory-verified. SUBJECTS AND METHODS: All patients who had more than one incisional oral mucosal biopsy diagnosed from 1975-1991 were abstracted from a database of all PML and SCC and their clinical records and biopsies reviewed. Patients were excluded if there was priorlsynchronous SCC or radiotherapy, frictional keratosis or lichen planus, missing clinical records/biopsy material or follow-up of <24 months. From the 50 suitable patients, gender, age, smoking status, site, clinical appearance and extent of lesion(s), treatment and year of diagnosis were recorded. Patients who developed SCC from PML were compared with those who did not. RESULTS: Squamous cell carcinoma occurred significantly more often in patients with single rather than multiple PML, those with 'non-homogenous' PML and in patients diagnosed prior to 1980. In Cox's survival analysis, only the clinical extent was predictive of SCC. CONCLUSIONS: Of all the features considered in our series, size (extent) was the most important clinical factor in determining the risk of future SCC in PML, particularly when several adjacent anatomical sites were affected.