Incidental diagnosis of very small rectal neuroendocrine neoplasms: when should endoscopic submucosal dissection be performed? A single ENETS centre experience.

The management of small (≤5 mm) rectal neuroendocrine neoplasms (r-NENs), incidentally removed during colonoscopy, still remains under debate. All consecutive patients affected by r-NENs from January 2013 to December 2017 were studied. The inclusion criteria were: (1) patients having an incidental pathological diagnosis of very small (≤5 mm) polypoid r-NENs; (2) patients treated with a standard polypectomy as first-line therapy and (3) patients treated by endoscopic submucosal dissection (ESD) as salvage therapy. The primary endpoint was to identify the factors related to residual disease after a standard polypectomy. The secondary endpoint was to calculate the accuracy of endoscopic ultrasound (EUS), grading and size in predicting residual disease. Starting from a prospective database of 123 consecutive patients affected by r-NENs, only 31 met the inclusion criteria. A final pathological examination of an ESD specimen showed residual disease in 7 out of 31 patients (22.6%). A multivariate analysis showed that the size of the polyps was the only independent factor related to residual disease with an odds ratio of 8.7 ± 7.5 (P = 0.013) for each millimetre. The accuracy of EUS, grading and tumour size (3.1 mm cut-off point) and area under the curves were 0.661 ± 0.111, 0.631 ± 0.109 and 0.821 ± 0.109, respectively. When the r-NEN polyp was larger than 3 mm, ESD was indicated. Unlike the size of the tumour, grading and EUS features did not accurately predict residual disease.