Leiomyoma-like clip artifact after endoscopic full-thickness resection

An endoscopic full-thickness resection with FTRD system (Ovesco Endoscopy, Tübingen, Germany) was performed in a 69-year-old man with a granular laterally spreading tumor (G-LST) with non-lifting sign in the ascending colon. Histology showed a low-grade dysplasia tubulovillous adenoma, R0 resection. At surveillance colonoscopy after 12 months, the clip was found with a polypoid tissue with regular mucosal surface pattern trapped inside. Since the length of time the clip was left in place ensured proper healing and in order to avoid any recurrence of adenoma in the area, the polypoid lesion and the clip were resected en bloc. The histological study revealed a polypoid formation with muscular tissue surrounded by healthy mucosa, suggesting a leiomyoma. Immunohistochemical actine staining confirmed the presence of muscularis mucosae and the muscularis propria inside the polypoid lesion, due to a full-thickness clip entrapment of the colon wall, with the development a leiomyoma-like clip artifact. The presence of foreign bodies such as clips at the resection site may produce artifacts leading to confusion in the diagnosis as in this case in which it has been able to produce an abnormal growth of the muscularis propria. The detection of a clip artifact leiomyoma has not yet been reported and highlights the importance of transmitting correct information about the case and the technique to the pathologist in order to achieve a correct diagnosis.