Expression of bcl-2 and p53 in de novo and ex-adenoma colon carcinoma: a comparative immunohistochemical study

The development of colorectal carcinoma from adenomas is recognized as the dominant mechanism of colon carcinogenesis. However, early colon carcinomas are being increasingly detected which have no adenomatous elements in their vicinity, and which, despite their small size, already show submucosal invasion. Such tumours (so-called 'de novo' carcinomas) have renewed consideration of the de novo colorectal carcinogenesis pathway. The goal of this study was to evaluate the expression of tumour suppressor gene p53 and apoptosis control gene bcl-2 in de novo carcinomas, compared with early carcinomas developing in the background of an adenoma (ex-adenoma). Fifty cases each of de novo and ex-adenoma carcinomas (pT1) were studied. p53 expression was significantly higher in the de novo carcinomas than in the ex-adenoma carcinomas (62 per cent vs. 42 per cent), while bcl-2 tended to be weaker in the de novo than in the ex-adenoma carcinomas. These differences' support the concept that de novo carcinomas are a unique pathological entity, with a phenotype reflecting their more aggressive behaviour.