Pseudoinvasion in an Adenomatous Polyp of the Colon Mimicking Invasive Colon Cancer

Pseudoinvasion or pseudocarcinomatous invasion in an adenomatous polyp of the colon can be unfamiliar to an endoscopist. Pseudoinvasion in an adenomatous polyp represents prolapse of the adenomatous epithelium into its stalk. In most cases its morphology does not differ from of general adenomatous polyps, but in some cases it can morphologically mimic a malignant polyp with submucosal invasion due to mass- like lesioning of its stalk. This makes it difficult for endoscopists to differentiate pseudoinvasion in an adenoma from an invasive carcinoma by conventional endoscopy; instead, endoscopic ultrasonography can provide useful information for differentiating these conditions. We report on an 82-year-old man who presented with a large pedunculated polyp with a thick stalk in the sigmoid colon, which mimicked a submucosal invasive carcinoma. The patient was diagnosed with pseudoinvasion in an adenomatous polyp after segmental resection of the sigmoid colon.

A Case of Pseudoinvasion in Peutz-Jeghers Polyposis

Peutz-Jeghers polyp with pseudoinvasion is characterized by the presence of mucosal islands within muscle layer often associated with mucinous cysts. It occurs when mucosal components completely penetrate the muscularis propria, and shows no cytologic signs of malignancy. In most instances, the lesion may be the result of forces exerted during intussusception in the involved small intestine. We describe a case of Peutz-Jeghers polyposis with pseudoinvasion in a 24-year-old female patient. This patient presented with intussusception and a segmental resection of the ileum was performed. Microscopically, it disclosed a hamartomatous polyp with pseudoinvasion. There were glandular islands and mucinous cysts embedded within the bundle of muscle, layer, extending, to the subserosa. There was o evidence of cellular dysplasia or desmoplasia.