Adverse Histologic Features in Colorectal Nonpedunculated Malignant Polyps With Nodal Metastasis

Abstract

Tumor differentiation, lymphovascular invasion, margin status, polyp shape, and size are important parameters of malignant polyps (pT1) indicating possible node metastasis, which justifies a surgery. However, the size, margin, and lymphovascular invasion are often unknown or difficult to assess in a piecemeal polypectomy from a nonpedunculated malignant polyp. The aim of the study was to identify adverse histologic features in nonpedunculated malignant polyps associated with an increased risk of nodal metastasis, which may warrant a colectomy procedure. A total of 24 node-positive and 18 node-negative nonpedunculated malignant polyps and their corresponding subsequent resection specimens from 2005 to 2018 were reviewed. Cases with node metastasis were more often positive for high-grade tumor budding (70.8% vs. 16.7%; P=0.0005), poorly differentiated clusters (54.2% vs. 22.2%; P=0.0369), and both high-grade tumor budding and poorly differentiated clusters (45.8% vs. 11.1%; P=0.0160) compared with controls without nodal metastasis. High-grade tumor budding, poorly differentiated clusters, and combined high-grade tumor budding and poorly differentiated clusters increased the risk of nodal metastasis, with odds ratio of 12.1, 4.1, and 14.3, respectively. Furthermore, nodal metastasis could be seen in subsequent colectomy specimen even in completely excised malignant polyps with adverse histologic features. Our findings indicate that high-grade tumor budding and poorly differentiated clusters are important adverse histologic risk features in predicting lymph node metastatic potential. These histologic features should be reported and it may warrant a colectomy when they are present.

Poorly differentiated clusters in colorectal cancer: a current review and implications for future practice

“…A recent study of 42 non-pedunculated malignant polyps (24 with lymph node metastasis and 18 without) evaluated a novel grading system for PDC, defining 'high-grade PDC' as ≥5 PDC in a 920 field. 26 Cases with LVI were excluded. High-grade PDC was significantly associated with lymph node metastasis (with rates of 76% versus 44% for high-and low-grade PDC, respectively).…”

“…All 12 studies found PDC grade to be significantly associated with adverse clinical outcome as well as other adverse histological features. 1,3,4,7,8,14,23,24,26,[30][31][32] By contrast, only three studies found a significant association between conventional histological grade and adverse outcome. 3,7,14 In two of these studies, PDC grade was superior to conventional histological grade in predicting adverse outcomes.…”

Malignant Colorectal Polyps

“…Patients with T1 colorectal cancer after endoscopic polypectomy have lower morbidity and mortality rates, with improved oncologic outcomes with a 5-year survival rate of more than 90%, leading us to question the additional benefit of surgical resection for these patients. 1,9,11 Despite these findings, it is important to remember that endoscopic therapy will be insufficient and incomplete in case of lymph node metastasis, which occurs in 7% to 20% of patients with T1 colorectal cancer. 12,13 For this purpose, the quality of pathology reports must be standardized and is essential for the consequent treatment decision.…”

Interobserver Variability in Assessment of Depth of Submucosal Invasion for Colonic Endoscopic Resections Among Subspecialized Gastrointestinal Pathologists

“…[1][2][3][4][5] The pathologic criteria for cure of an endoscopically resected pT1 colonic adenocarcinoma include clear margins, along with low-grade histologic features, that is, lack of high-grade morphology or tumor budding, and no lymphovascular invasion. 3,[5][6][7][8][9][10][11][12][13][14][15][16] Recently, it has been suggested that, in the absence of the aforementioned features, depth of submucosal invasion 1000 lm or more may be an indication for colectomy whereas tumors that invade less than 1000 lm can be managed conservatively with surveillance. 17 The project study by the Japanese Society for Cancer of the Colon and Rectum (JSCCR) reported that nodal metastases occurred in 12.5% of CRCs with a submucosal depth of invasion 1000 lm or greater.…”