A 69-year-old man was submitted to an en bloc endoscopic mucosal resection (EMR) of a 20-mm non-granular laterally spreading tumor, Paris Classification 0-IIa+c, located in the sigmoid colon (Fig. 1A). Immediately after EMR an imminent colonic perforation was identified: examination of the mucosal defect revealed a mirror target sign (Fig. 1B). The defect was successfully closed with 5 endoscopic clips (Fig. 1C). The specimen was retrieved and the target sign was confirmed on examination of the underside of the lesion (Fig. 1D). The patient was discharged 6h after uneventful clinical surveillance. Histopathological assessment revealed a high-grade dysplasia tubular adenoma without submucosal invasion and clear margins (Fig. 2A), confirming partial muscularis propria (MP) resection (Fig. 2B).
Colonic perforation may occur in up to 10% of EMR and endoscopic submucosal dissections. The target sign, an easily recognizable endoscopic marker of the MP resection, indicates a potential risk for colonic perforation. The mirror target sign is characterized by the presence of 2 concentric white rings in the mucosal defect: the inner ring, corresponding to the point of MP resection, and the outer ring corresponding to the site of cauterized mucosa.1
Early identification of this sign allows prompt endoscopic closure, avoiding one of the most feared complications – colonic perforation. As so, it constitutes an endoscopic diagnostic tool with important clinical value.
