Colorectal Polyps

Abstract

Describe the current general classification of colon polyps. Which features of an adenomatous polyp correlate with greater malignant potential? Colorectal polyps are classified histologically as neoplastic or non-neoplastic (Table 1). The majority of polyps are small, non-neoplastic lesions that are found during screening or when procedures are performed for other diagnostic reasons (for example, a gastrointestinal bleed). The malignant potential and subsequent screening intervals are dependent on polyp type. All adenomas have variable degrees of dysplasia ranging from low-grade to highgrade. Classically, it is believed that the malignant potential of adenomas correlates with type of polyp, size, and degree of dysplasia. Higher grades of dysplasia, increasing percentage of villous tissue within the polyp, and polyps greater than 1 cm in diameter are associated with increased risk of malignancy. A polyp is considered malignant when cancer cells within the neoplasm have extended to the submucosa via penetration through the muscularis mucosal layer. The adenoma-carcinoma sequence has traditionally been characterized as a uniform progression from normal mucosa, to adenoma, to carcinoma through an underlying homogenous carcinogenic pathway. The process of adenoma development is initiated when both copies of the adenomatous polyposis coli (APC) tumor suppressor gene are deactivated in a single epithelial cell. The consequent lack of the suppressor permits activation of oncogenes, including, but not limited to, p53 and k-ras. There is evidence, however, that colorectal carcinogenesis is a heterogeneous process involving more than one precursor lesion.

Demographic And Histopathological Characteristics Of Colorectal Polyps: A Descriptive Study Based On Samples Obtained From Symptomatic Patients

“…Within adenomas, the proportion of villous type -a direct precursor of CRC -increased remarkably with age. Further, adenomas found in older patients had in ~56% of cases high-grade dysplasia and were > 1 cm large (both indicators of a high malignant potential) (11). A direct comparison of our findings with previous studies is challenging due to differences with regard to study period and population (in terms of age, gender and ethnicity).…”

Expression of neutrophil gelatinase-associated lipocalin in colorectal neoplastic progression: a marker of malignant potential?

“…The framework of sporadic colorectal cancer is the adenoma–carcinoma sequence, describing the change from histologically normal cells to pre-malignant adenomatous epithelium exhibiting increasing degrees of cell dysplasia to overt invasive malignant disease (Fearon and Vogelstein, 1990; Leslie et al , 2002). The pre-malignant phenotype, colorectal adenomatous polyps, exerts characteristics that denote high-malignant potential, such as increasing size, increasing degree of cell dysplasia and greater villous content (O'Brian et al , 1990; Colucci et al , 2003; Giuliani et al , 2006). These features are central to the current guidelines on patient management and specifically interval of surveillance colonoscopy (Cairns et al , 2010).…”

Epigenetic silencing of miR-137 contributes to early colorectal carcinogenesis by impaired Aurora-A inhibition

“…Our results showed that miR-137 is down-regulated in colon polyps, supporting the conclusion of the early silencing of miR-137 in colorectal adenoma. According to the histological studies, colorectal polyps can be simply classified into two groups–non-neoplastic and neoplastic polyps–according to their malignant potency [30]. Importantly, the expression level of miR-137 is gradually decreased in hyperplastic, tubular and villous polyps (Figure 7B and Table 3).…”