For patients with malignant colorectal polyps, endoscopists should look for features of deep submucosal invasion and should retrieve, handle, and submit specimens in ways that support thorough and accurate pathologic assessment, according to new recommendations from the US Multi-Society Task Force on Colorectal Cancer.
“In nonpedunculated lesions with features of deep submucosal invasion, endoscopic biopsy is followed by surgical resection. In cases without features of deep submucosal invasion, en bloc resection and proper specimen handling should be considered (if feasible) for lesions with a high risk of superficial submucosal invasion,” wrote Aasma Shaukat, MD, MPH, of the Minneapolis Veterans Affairs Health Care System and her fellow experts. The recommendations were published in Gastroenterology.
Malignant colorectal polyps invade the submucosa but do not extend into the muscularis propria. Pedunculated and nonpedunculated polyps should be considered to invade the deep submucosa if they are classified as NICE (NBI International Colorectal Endoscopic) type 3, Kudo type VN (neoplastic and invasive, with an irregular arrangement), or Kudo type VI (an amorphous structure, with a loss of or decrease in pits). “Nonpedunculated lesions with these features should be biopsied (in the area of surface feature disruption), tattooed (unless in or near the cecum), and referred to surgery. Pedunculated polyps with features of deep submucosal invasion should undergo endoscopic polypectomy,” according to the MSTFCC recommendations.
Moderate-quality evidence links submucosal invasion with two types of polyp morphology: LST-NG (laterally spreading tumor, nongranular type) showing a depression or sessile shape and LST-G (laterally spreading tumor, granular type) that includes a dominant nodule. According to low-quality evidence, these lesions should be managed with en bloc rather than piecemeal resection. En bloc resection is important for all pedunculated polyps (even if large) and should be considered for LST-G lesions with a dominant nodule. Resected pedunculated polyps should be retrieved through the suction channel – if doing so does not require them to be cut – or with a net or snare during scope withdrawal. Nonpedunculated lesions with suspected submucosal invasion that are removed en bloc should be pinned peripherally around the entire circumference to a hard surface and fixed in 10% formalin. This practice helps pathologists orient specimens to correctly assess depth of invasion and margin involvement.
For both pedunculated and nonpedunculated polyps, features denoting a high risk for residual or recurrent malignancy are poor tumor differentiation, lymphovascular invasion, or more than 1 mm of submucosal invasion. For nonpedunculated polyps, additional high-risk features include tumor budding and tumor involvement of the cautery margin. The MSTFCC recommends that, when reporting on a malignant colorectal polyp, pathologists follow the structured template of the College of American Pathologists and note the lesion’s histologic type, grade of differentiation, extent of tumor extension or invasion, stalk and mucosal margin, and presence or absence of lymphovascular invasion. Specimen integrity, polyp size and morphology, and tumor budding are also useful. To reduce miscommunication and facilitate appropriate management, pathologists should avoid using the terms carcinoma and cancer when describing malignant colorectal polyps, according to the MSTFCC.
The decision to recommend adjuvant surgery “is based on polyp shape, whether there was en bloc resection and adequate histologic assessment, the presence or absence of unfavorable histologic features, the patient’s risk for surgical mortality and morbidity, and patient preferences,” the recommendations state. Because multidisciplinary management can optimize clinical outcomes for patients with malignant polyps, gastroenterologists, pathologists, oncologists, and surgeons should identify best ways to communicate with each other and share decision-making conjointly and with patients. “Patient values are important in cases where the risk of residual cancer and the risk of surgical mortality are similar,” the MSTFCC notes. “In these latter cases, shared decision-making is emphasized.”
The authors of the task force recommendations reported having no relevant conflicts of interest since 2016.
SOURCE: Shaukat A et al. Gastroenterology. 2020 Nov 4. doi: 10.1053/j.gastro.2020.08.050