Evaluation of treatment for rectal neuroendocrine tumors sized under 20 mm in comparison with the WHO 2010 guidelines

Abstract

Abstract. Rectal neuroendocrine tumor (NET) is a relatively rare lesion of the gastrointestinal tract, but the prospective examination with colonofiberoscopy or endoscopic ultrasound has increased the frequency of its detection. It is often difficult to determine the optimal treatment for NETs sized <20 mm in the clinical setting. Other clinicopathological variables are not considered in the current guidelines and staging systems. Although the effects of lymphovascular invasion are not covered by the World Health Organization (WHO) 2010 guidelines or tumor-node-metastasis (TNM) staging system, this may be promising for the establishment of improved guidelines and staging systems, particularly for early-stage colorectal carcinoids. The aim of the present study was to evaluate rectal NETs sized <20 mm in comparison with the WHO 2010 guidelines. Between January 2005 and December 2013, 40 consecutive patients [26 men and 14 women; median age, 59.3 years (range, 34-81 years)] who underwent endoscopic resection of rectal NETs, and 12 patients undergoing surgical resection of rectal NETs, were enrolled in this retrospective study. The median tumor size was 7.4 mm (range, 3-15 mm). The locations of the NET were the rectosigmoid colon (n=3), the upper rectum (n=13), and the lower rectum (n=25). The NETs were classified by size as 0-5 (n=7), 6-10 (n=29) and 11-15 mm (n=4). The surgical procedures performed included low anterior resection plus esophagectomy (n=1), laparoscopic low anterior resection (n=7) and laparoscopic intersphincteric resection (n=4). Only 1 patient had lymph node metastasis (tumor sized 6-10 mm, with lymphovascular invasion). NET recurrence was not detected in any of the patients. According to the WHO guidelines, the tumors were classified as grade (G)1 (n=8), G2 (n=3) and G1/G2 (n=1). The tumor in the patient with lymph node metastasis was G1. NETs sized <10 mm may be curatively treated by endoscopic resection. However, NETs with either lymphovascular invasion or sized >1 cm carry a risk for metastasis equivalent to that of adenocarcinomas. Therefore, it is mandatory to histologically examine lymphovascular invasion in specimens retrieved via endoscopic resection to determine the necessity for further radical surgery with regional lymph node dissection. The treatment of NETs sized <20 mm as presently defined in the WHO 2010 guidelines requires further evaluation.

Management of Gastrointestinal Neuroendocrine Tumors

“…Formal surgical resection is recommended for tumors that are between 10 and 19 mm with high-risk features. 111,112 Additional criteria for formal surgical resection for rectal NETs include tumors ⩾20 mm, positive endoscopic resection margin(s), and lymphovascular invasion in patients receiving local treatment. 112 Formal resection options include low anterior resection (LAR) and abdominoperineal resection (APR).…”

Low-grade Rectal Neuroendocrine Tumor Recurring as Multiple Hepatic Metastasis after Complete Endoscopic Removal: A Case Report

“…[13][14][15][16] Based on these examples, regardless of how small the low-grade NET is, it is difficult to exclude the possibility of hidden metastasis completely.Therefore, the controversy regarding whether periodic follow-up is necessary is likely to persist.This case was distinct compared to previous reports in that the patient was in the state of 'cured'. The small, G1 NET lesion was resected completely by EMR, and there was no evidence of residual disease.…”

Rectal neuroendocrine tumor developing lateral lymph node metastasis after curative resection: a case report

“…However, 7-18.6% of lymph node metastases come from tumors < 10 mm in size [7,14,15]. Given that most of these tumors harbor lymphovascular invasion, Matsuhashi et al emphasized the importance of evaluating lymphovascular invasion of the resected specimen [16]. In the present case, the original tumor was 14 mm in size and had a depression on its surface.…”