The expression of p53 and bcl-2 in gastrointestinal stromal tumours is associated with anatomical site, and p53 expression is associated with grade and clinical outcome

Aims: To compare the expression of p53 and bcl-2 in gastrointestinal stromal tumours (GISTs) with anatomical site, National Institutes of Health (NIH) risk category (grade), pathological features, and clinical outcome. Methods and results: The immunohistochemical expression of p53 and bcl-2 in 105 GISTs (71 gastric, 20 small intestinal, four colonic, 10 rectal) was recorded. When all GISTs were assessed, there was p53 positivity in 28% and bcl-2 positivity in 77%. Gastric tumours had a lower prevalence of p53 positivity (20%) than intestinal (40-50%). Rectal GISTs had the lowest prevalence of bcl-2 positivity (20%) and gastric and small intestinal the highest (80% and 90%, respectively). In GISTs from all sites, p53 positivity was associated with size > 50 mm, epithelioid cell shape, nuclear atypia, mucosal invasion, and mitotic count > 5/50 high-power fields. In gastric GISTs the associations were the same, apart from size and mitotic count. In GISTs from all sites and in gastric GISTs, p53 expression correlated with NIH risk category. When GISTs from all sites were subjected to univariate survival analysis, an adverse outcome was associated with p53 positivity, NIH risk category, and several established prognostic factors. When gastric GISTs were assessed, the associations were similar although size was not prognostic. In multivariate survival analysis, p53 expression was independently prognostic for gastric GISTs in some models, while it was never independently prognostic for GISTs from all sites. Whether all GISTs or gastric GISTs were assessed, bcl-2 showed no association with clinical outcome or risk category. Conclusions: Anatomical site influences p53 and bcl-2 expression in GISTs. p53 expression is associated with NIH risk category, various pathological features, and clinical outcome, and may be independently prognostic for gastric GISTs. Bcl-2 expression has no prognostic value.