ABSTRACT
<p><b>OBJECTIVE</b>To introduce the WHO 2000 diagnostic criteria of biopsy of colorectal intraepithelial neoplasia and carcinoma and to enhance diagnostic accuracy and avoid overdiagnosis and underdiagnosis.</p><p><b>METHOD</b>The postoperative pathological examination and preoperative biopsy in 56 patients diagnosed as colorectal intraepithelial neoplasia and carcinoma before operation from January 2001 to October 2005 were compared retrospectively.</p><p><b>RESULTS</b>Among the 56 cases, 16 patients were diagnosed by preoperative biopsy as carcinoma in situ, intramucosal carcinoma and adenocarcinoma, but according to the new standard, of them 14 cases should be revised to be higher grade colorectal intraepithelial neoplasia.</p><p><b>CONCLUSIONS</b>Strictly adhere to the new WHO criteria, colorectal intraepithelial neoplasia and carcinoma can be diagnosed properly, but for the cases that submucosal muscular layer would not presented in biopsy, the diagnosis should be made by combining clinical findings and various examination results so as to avoid underdiagnosis and delay of treatment.</p>