Malignant colorectal polyps

Abstract

Nowadays, the number of cases in which malignant colorectal polyps are removed is increasing due to colorectal cancer screening programmes. Cancerous polyps are classified into non-invasive high grade neoplasia (NHGN), when the cancer has not reached the muscularis mucosa, and malignant polyps, classed as T1, when they have invaded the submucosa. NHGN is considered cured with polypectomy, while the prognosis for malignant polyps depends on various morphological and histological factors. The prognostic factors include, sessile or pedunculated morphology of the polyp, whether partial or en bloc resection is carried out, the degree of differentiation of the carcinoma, vascular or lymphatic involvement, and whether the polypectomy resection margin is tumor free. A malignant polyp at T1 is considered cured with polypectomy if it is a pedunculated polyp (Ip of the Paris classification), it has been completely resected, it is not poorly differentiated, the resection edge is not affected by the tumor and there is no vascular or lymphatic involvement. The sessile malignant polyp (Is of the Paris classification) at T1 is considered not cured with polypectomy. Only in some cases (e.g. older people with high surgical risk) local excision (polypectomy or endoscopic submucosal dissection or conventional endoscopic mucosal resection) is considered the definitive treatment.

Figure 1

The Haggitt classification. Haggitt 0: Limited to the mucosa without invasion of submucosa; Haggitt 1: Invasion of submucosa but limited to the head of the polyp; Haggitt 2: Invasion extending into the neck of the polyp; Haggitt 3: Invasion into any part of the stalk; Haggitt 4: Invasion beyond the stalk but above the muscularis propria.

Figure 2

Kitajima’s classification. The method used for measurement of submucosal invasion (SM) depth. A: For pedunculated submucosal invasive colorectal carcinoma, level 2 according to Haggitt’s classification was used as the baseline (grey line), and SM depth was measured as the vertical distance from this line to the deepest portion of invasion; B: For nonpedunculated, when the muscularis mucosae could be identified in HE stained specimens, the muscularis mucosae was used as baseline (grey line) and the vertical distance from this line to the deepest portion of invasion represented with bidirectional arrow grey; C: For nonpedunculated, when the muscularis mucosae could not be identified due to carcinomatous invasion, the superficial aspect of the invasive carcinoma was used as baseline (grey line), and the vertical distance from this line to the deepest portion of invasion was determined (bidirectional arrow grey).

Figure 3

Diagnostic and therapeutic algorithm of malignant polyps.