采用扩增片段限制性长度多态性分析（Amp－RFLP）和流式细胞分析技术（FCM）对直肠癌切除标本、癌旁远端肉眼观察“正常”的肠组织及正常肠粘膜，结合病理资料，比较其细胞DNA倍体性、S期百分比和增殖指数，检测K－ras基因12位密码子点突变，结果表明：直肠癌是进展迅速的恶性肿瘤，细胞增殖活性异常升高；K－ras基因突变是伴随直肠癌的一种基因异常表现，癌旁组织出现基因水平的异常发生在组织形态学和细胞动力学改变之前，是癌变发生的早期行为。 Amplified fragment restriction length polymorphism analysis (Amp-RFLP) and flow cytometric analysis (FCM) were used to examine the “normal” intestinal tissue and normal intestinal mucosa of the resection specimens of the rectal cancer and the distal side of the tumor. Data, comparing their cell DNA ploidy, percentage of S phase and proliferation index, detected K-ras gene codon 12 mutations, the results show that: rectal cancer is a rapidly progressing malignant tumor, abnormal cell proliferation activity; K- The ras gene mutation is a gene abnormality associated with rectal cancer. Abnormalities in the gene expression adjacent to the tumor occur before changes in histomorphology and cellular dynamics, and are the early behaviors of carcinogenesis.