Surgery for colorectal polyps: histological features, current indications, critical points, future perspective and ongoing studies.

The main difference between benign and maligant colorectal polyps is the risk of lymphatic and haemotogeneous spread through the submucosal vessels. Malignancy is defined as invasion beyond the muscularis mucosae. In contrast, the benign polyps are confined to the mucosa without crossing the muscolaris mucosae and they have been usually classified as intramucosal neoplasia [1,2]. Interestingly, a limited number of lymphatic vessels are present in the deeper mucosa level, maintaining an intimate association with the muscolaris mucosa [3]. Nevertheless there are no known reliable examples of intramucosal lesion that have given rise to nodal or distant metastases. Accordingly, in situ adenocarcinoma and intramucosal adenocarcinoma are not regarded as malignant. These terms should be abandoned and included under the definition of dysplasia [1,2].