Background and aim: The risk of lymph node metastasis of a small rectal carcinoid tumor (<10 mm) is known to be lower than that of tumors at other gastrointestinal sites. Although rectal carcinoid tumors can be treated by endoscopic resection, the resected specimen may be incomplete. The consequences of an incomplete resection are not well known.
Method: From December 2008 to November 2015, cases of rectal carcinoid tumors resected by endoscopic resection techniques such as endoscopic submucosal dissection (ESD), or endoscopic mucosal resection using band ligation device (EMR-L), or cap aspiration (EMR-C) were enrolled. The factors associated with incomplete endoscopic resection and clinical outcomes were retrospectively analyzed.
Results: During the study period, a total of 134 rectal carcinoid tumors were resected by endoscopic techniques; ESD (n = 53), EMR-C (n = 65), and EMR-L (n = 16). The mean tumor size was 5.5 ± 2.4 mm. The mean follow-up period was 835 ± 501 days. The en bloc resection and complete resection rates were 100 and 85.8%, respectively. Procedure time was longer and the size of the resected tumor was larger in the ESD group than in the EMR-C or EMR-L (p < 0.001) group by the univariate analysis. A factor related to incomplete resection was central depression on the surface (OR 11.529, 95% CI 2.377-55.922, p = 0.002), as revealed by the multivariate analysis. Nineteen patients had an incomplete resection status and did not undergo additional resection treatment; none of these patients had recurrence during the study period.
Conclusions: A rectal carcinoid tumor with a central depression on the surface was associated with a higher incomplete resection rate. After an incomplete resection of small rectal carcinoid tumors, without evidence of lymphovascular invasion, a periodic follow-up examination without additional resection may be recommended.
Keywords: Carcinoid tumor; Endoscopic mucosal resection; Endoscopic submucosal dissection; Incomplete resection.