Malignant adenoma: diagnosis, staging, risk factors, lymph node involvement and problems of sampling.

Colorectal adenoma containing invasive carcinoma corresponds to a carcinoma invading the submucosa and represents the earliest form of clinically relevant colon cancer. Despite the generally favourable course after endoscopic removal, a limited risk of developing lymph node metastases still exists and the correct histologic assessment of malignant polyps can help in defining the evolutive potential. At present, histopathologic parameters alone determine whether a high (35%) or low (7%) risk of nodal metastases exists and the most relevant diagnostic criteria are the grade of differentiation of invasive adenocarcinoma, vascular invasion, the level of invasion of carcinomatous cells and the status of the resection margin.