OVEREXPRESSION OF P53 IN NORMAL ORAL-MUCOSA OF ORAL-CANCER PATIENTS DOES NOT NECESSARILY PREDICT FURTHER MALIGNANT DISEASE

Recent reports of p53 positivity in the normal mucosa of some head and neck cancer patients have been taken as evidence for field cancerizat ion and hence a likelihood of the development of further tumours, yet few papers report the clinical significance of this finding through lo ng-term follow-up. The immunohistochemical detection of p53 expression in clinically and histopathologically normal oral mucosa taken from t he wound margin following excision of oral cancer,vas assessed using t he polyclonal antibody CM1. Fresh frozen biopsies of normal oral mucos a and the corresponding tumour from 21 oral cancer patients and of nor mal mucosa from 25 non-cancer patients were assessed for p53 overexpre ssion. The 'normal' mucosa was positive in 12 of the oral cancer patie nts and one of the non-cancer patients. Second malignant rumours were seen in patients from whom p53-positive 'normals' and p53-negative 'no rmals' were recorded. In five of the p53-positive 'normals', the corre sponding cancer was p53-negative. In one case, where 'normal' mucosa w as available from more than one site, one region was positive, whilst the other was negative. No obvious difference in age, tobacco use, or recurrence rate was seen between positive and negative cases. All pati ents who were still alive were reviewed for a minimum of 5 years. Usin g Fisher's exact test, no statistically significant difference was fou nd for the rate of second malignant tumours occurring in patients with p53-positive compared with p53-negative normal mucosa. Thus, the dete ction of p53 in normal mucosa did not necessarily predict a further tu mour. (C) 1997 by John Wiley & Sons, Ltd.