Clinical outcome of low- and high-risk malignant colorectal polyps: results of a population-based study and meta-analysis of the available literature

Some histological features of malignant polyps have been used to classify patients into low- and high-risk groups. This study proposed to evaluate the impact of this classification on the clinical outcome of patients with malignant polyps. Through the Colorectal Cancer Registry, 105 patients with endoscopically removed malignant polyps were selected. The presence of one of the following histological features defined malignant polyps as high-risk: infiltrated resection-margin, poorly differentiated carcinoma, lymphatic/vascular invasion and tumour budding and depth of submucosal invasion. Available literature was reviewed by applying a similar classification. Most of the malignant polyps were pedunculated and were localized in the left colon. Fifty-five malignant polyps were classified as low-risk lesions and 50 as high-risk. None of the patients at low-risk died of colorectal cancer. Of the patients at high-risk, three died of cancer; all three cases showed lymphatic/vascular invasion. Review of the literature reveals that an unfavourable clinical outcome is significantly more prevalent in the high-risk compared with the low-risk group (p > 0.005). Moreover, all histological risk factors show a specific predictive value of clinical adverse outcome. Our study and the pooled data analysis confirmed the usefulness of the subdivision into low- and high-risk malignant polyps for management of patients with endoscopically removed colorectal carcinoma.