Field cancerisation of the oral cavity: comparison of the spectrum of molecular alterations in cases presenting with both dysplastic and malignant lesions.

Dysplastic lesions and invasive oral squamous cell carcinoma (SCC) from patients with field change were screened by restriction fragment length polymorphism (RFLP) and microsatellite assay. All tumours contained more genetic changes than the matched dysplasia which are likely to represent progression. Four of the 15 dysplastic lesions harboured the same abnormalities detected in the tumour and some paired lesions showed identical novel microsatellite alleles. The finding of identical 'genetic fingerprints' in dysplastic lesions and invasive carcinoma from the same patient provides strong evidence that these dysplasias are precursor lesions and that multiple lesions have probably arisen due to transfer of the progeny of an altered cell. Eight of the 15 dysplastic lesions showed alterations which were not present in the matched cancer, showing that evolution of subclones, or fusion of multiple clones also occurs. A further case showed loss of different alleles in the paired samples. These findings highlight the complexity of the genetic abnormalities present in the mucosa of patients with field change and suggests that the origin of these altered foci may be diverse.