EXPRESSION OF P53 IN EARLY (T1) GASTRIC-CARCINOMA AND PRECANCEROUS ADJACENT MUCOSA

Abnormalities of the tumour suppressor gene p53 have been shown in app roximately 60% of advanced gastric adenocarcinomas and it has been sug gested that the immunohistochemical finding of increased p53 expressio n is a prognostic marker in gastric cancer. No studies of early (T1) t umours have been reported. Over expression of p53 protein in 95 early gastric carcinomas and in adjacent mucosa was investigated using immun ohistochemistry with antibody CM1. Thirty five per cent of the tumours were positive. The frequency of p53 positivity in tumours of tubular histological type (46%) was significantly higher than that in signet r ing tumours (10%) (p=0.006), and neoplasms that invaded deeply into th e submucosa were more frequently positive (45%) than others (30%). Fiv e of eight (62%) T1 tumours with lymph node metastases showed immunore active p53. In signet ring tumours, immunopositivity correlated with t he frequency of DNA aneuploidy. p53 Over expression was also found in 15% of 26 examples of high grade dysplasia in mucosa adjacent to invas ive tumours. No positivity was found in intestinal metaplasia or in no rmal mucosa. The findings show that immunocytochemically demonstrable over expression of p53 correlates with other morphological markers of aggressiveness in T1 gastric adenocarcinoma. The increasing frequency of p53 immunoreactivity in the sequence of high grade dysplasia-->earl y gastric cancer-->advanced gastric cancer supports the view that abno rmalities of p53 are related to tumour progression in gastric carcinog enesis.