Polypoid nodule scar after gastric endoscopic submucosal dissection: results from a multicenter study.

 A post-endoscopic submucosal dissection (ESD) scar is expected to look homogeneous, however, some patients develop benign polypoid nodule scar (PNS). Incidence of PNS is unknown, yet these scars have direct clinical implications because they may render evaluation of post-ESD neoplastic recurrence difficult. Therefore, we reviewed the clinical experience of 5 ESD referral centers and evaluated their PNS incidence and clinical management.  This was a retrospective multicenter case series enrolling patients that underwent R0, curative gastric ESD from 2003 to 2015 in 5 academic centers. PNS was defined as ESD site nodularity with hyperplastic or regenerative tissue histology.  A total of 2275 patients underwent gastric ESD with endoscopy control and 28 patients (18 men/10 women) developed PNS for overall incidence of 1.2 %. Incidence of PNS ranged from 0.15 % to 11.4 % between centers. All patients that developed PNS had primary neoplastic lesions located in the distal stomach. Considering only lesions situated in the antrum (n = 912), incidence of PNS was 3.1 %. After mean follow-up of 43 months (range 6 - 192), no malignant recurrence in the PNS has been identified. In five patients (17.8 %) PNS disappeared after a mean of 18 months.  PNS occurs exclusively after ESD in the distal stomach in approximately 3.1 % of patients. Although PNS appearance can be concerning, no malignant recurrence was observed after curative R0 resection. Therefore, PNS should be viewed as a benign alteration that does not require any type of intervention, other than endoscopic surveillance.