PSEUDOINVASION, A HISTOLOGICAL DIAGNOSIS TO CONSIDER IN THE ENDOSCOPIC SUBMUCOSAL DISSECTION

A 34-year-old female patient, referred to our center for endoscopic submucosal dissection (ESD) of non-granular laterally spreading rectal tumor (LST-NG) of 20 × 30 mm, with a central depression (paris 0-IIa+IIc) (Photo 1). After characterization by endoscopist with more than 300 ESD (photo 2), he performed this technique during a Live-Endoscopy in vivo. LST was resected in a piecemeal, because the lesion had a depression with severe fibrosis and could not be lifted enough. The histological findings showed a tubular adenoma with signs of pseudoinvasion, discarding after the complete analysis any foci of high grade dysplasia or adenocarcinoma.

Adenomatous polyps with pseudoinvasion result from trauma that produce and prolapse of adenomatous epithelium in areas of defective or weak muscularis mucosae into their stalk (Ferreira da Silvaa M, GyH 2017), giving the appearance of invasion and usually considered as neoplastic lesions. It is known, polyps with pseudoinvasion are frequently pedunculated and located in the sigmoid colon, although there are few published cases. (Tanizawa T, 2003). The definitive diagnosis is by histology, where the misplaced epithelium glands are similar to the adenoma.

Given the scarce published literature, it is important to maintain the concept of polyp with pseudoinvasion present when considering ESD, even performed for experienced endoscopist.