Clinical outcomes of rectal neuroendocrine tumors ≤ 10 mm following endoscopic resection

Background and study aims: This study was conducted to determine the clinical outcome of rectal neuroendocrine tumors (NETs) ≤ 10 mm following conventional endoscopic resection.

Patients and methods: A total of 107 patients who underwent conventional endoscopic treatment for rectal NETs (median size 5.0 mm [range 1.0 – 10.0]) were followed up for a median of 31 months (range 13 – 121). The following data were analyzed: lesion characteristics, clinical outcomes, and histological features determined using tissue microarray analysis (TMA), including the mitotic count and the Ki-67 index.

Results: En bloc removal was achieved for all tumors, and the complete resection rate was 49.5 % (53 /107). Resection margin status was indeterminate in 37 patients (34.6 %) and positive in 17 (15.9 %). Rectal NETs in 71 patients demonstrated a score of ≤ 2 % on the Ki-67 index and < 2 for mitotic count on TMA. In another 28 tumors that did not undergo TMA, the mitotic count was 0 – 1 per 10 high-power fields. Neither recurrence nor metastasis was noted during the follow-up period following resection.

Conclusions: Rectal NETs (≤ 10 mm in size) appear to demonstrate benign behavior based on the mitotic count and the Ki-67 index. These results suggest that the outcome of rectal NETs (≤ 10 mm in size) following conventional endoscopic resection might be comparatively excellent, regardless of the resection margin status. However, long term follow-up data are required to confirm this.

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