Rectal adenomas containing invasive adenocarcinoma extending though the muscularis mucosae into the submucosa have been defined as "malignant polyps". These polyps constitute a form of early (i.e., curable) rectal carcinoma. Various opinions exist for managing patients after endoscopic removal of malignant polyps. One possibility is that all patients with malignant polyps should undergo standard resection ; another opinion is that a conservative approach should be maintained under the condition of an absence of cancer at the resection line . Malignant polyps removed by endoscopic polypectomy require evaluation of histologic parameters that have been determined to be significant prognostic factors related to the risk of adverse outcome (i.e., lymph node metastasis or local recurrence from residual malignancy) after polypectomy [4, 26, 38, 66-80]. Pathologic features having independent prognostic significance and that are crucial for evaluating risk of adverse outcome and determining the possible need for surgical treatment include histolog-ic grade, level of invasion of the submucosa, status of resection margin, and lymphatic-venous vessel involvement. A matter of controversy involves which parameters should be integrated into such criteria relating to tumour aggressiveness such as tumour "budding" and extension (width and depth) of invasion in the submucosal layer.
By using 3 qualitative parameters for cancer (tumour grade, vascular invasion and budding) we might be able to select patients having a lower possibility of nodal involvement. The absence of an unfavourable tumour grade, definite vascular invasion and tumour budding would be the most informative combination of criteria for selecting patients with low recurrence risk and are ideal for conservative approaches. The nodal involvement rate is 0.7%, 20.7% and 36.4% if one, two or all three parameters are unfavourable .
Numeric data regarding extent of submucosal invasion aid in choosing tumours having very little risk for nodal involvement (width of submucosal invasion <4000 |im; depth of submucosal invasion <200 |im) in patients with an absence of unfavourable parameters .
Ueno [82,83] has also reported that the qualitative parameters observed in the biopsy specimens of the submucosal horizontal invasive frontal region in advanced rectal cancers are relevant to the extent of extramural and intramural spread. It can be assumed that these parameters are appropriate to evaluate the potential for invasion and metastasis.
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