Significantly different bcl-2 expression profiles in gastric and non-gastric primary extranodal high-grade B-cell lymphomas

Fifty-five cases of primary extranodal high-grade B-cell non-Hodgkin's lymp homa were investigated for bcl-2 and p53 protein expression as well as for t(14;18) translocations and p53 mutations. Phenotypic and genotypic profile s were compared between tumours of gastric (27 cases) and non-gastric (28 c ases) origin. bcl-2 protein expression was significantly lower in gastric ( 11/27) than in non-gastric (28/28) lymphomas (p < 0.0001), while nuclear p5 3 protein expression did not differ significantly between these two groups. In the stomach, there were no significant differences in either bcl-2 or p 53 expression profiles between high-grade lymphomas with (n=14) and without (n=13) evidence of a low-grade component of MALT type, However, secondary high-grade lymphomas showed a significant down-regulation of bcl-2 protein (p < 0.0001) and, conversely, an up-regulation of p53 protein (p < 0.0001) as compared with their low-grade tumour components. In extranodal high-grad e B-cell lymphomas, bcl-2 protein expression was not associated with t(14;1 8) translocation. Only one gastric lymphoma had a p53 point mutation with p otential alteration of the amino acid sequence. These findings indicate tha t primary gastric high-grade B-cell lymphomas are immunohistologically dist inct from primary extranodal high-grade B-cell lymphomas of an origin other than in the stomach, Copyright (C) 2000 John Wiley & Sons, Ltd.