Sessile Serrated Adenoma of the Appendix in an Asymptomatic Patient

Abstract

A 63 year-old Hispanic male with history of hypertension and nephrolithiasis presented for an averagerisk colorectal cancer screening colonoscopy. During the study he was found with a large, raised submucosal lesion in cecum, specifically arising at the appendiceal orifice with a “volcano sign” appearance as seen in mucocele of the appendix (Image 1). Epithelial biopsy of this lesion was taken and reported a serrated adenomatous tissue. An abdominopelvic CT described a distended appendix with intraluminal fluid density. Occluding its orifice, there was a polypoid density measuring 2.0 cm x 2.3 cm x 1.7 cm with Hounsfield units compatible with soft tissue density (Image 2). There was no adjacent lymphadenopathy or focal inflammatory changes. An appendiceal mucocele as well as an obstructing adenocarcinoma were considered in the differential diagnosis. The patient underwent a laparoscopic right hemicolectomy. Pathology report confirmed a vermiform appendix with a sessile serrated adenoma occupying the entire length of the appendix, unremarkable margins of excision and lymph nodes (Image 3). Sessile serrated adenomas are a relatively recent described entity most commonly occurring in the right colon and rarely in the appendix. The term serrated adenomas originate from its histological findings of adenomas with saw tooth-like dysplastic epithelium found in more than 50% of basal crypts. It has been recognized that these lesions portraits microsatellites instability, which is a molecular pathway different from conventional adenomas and a risk factor for colorectal cancer. From 20 to 30% of colorectal cancers arise through the serrated polyp pathway. In the first small case series reported by Rubio in 2004, most serrated and villous adenomas of the appendix were diagnosed as incidental findings during appendectomy and autopsy, and appeared to be highly aggressive lesions in comparison to those arising from the colorectum. Except for rare case reports and a few case series, the true incidence of appendiceal serrated polyps is unknown. This case report describes a sessile serrated adenoma located in the appendix diagnosed by a screening colonoscopy and successfully treated by surgical resection.Figure: Endoscopic findings of a raised submucosal lesion arising at appendiceal orifice.Figure: The appendix is distended by intraluminal fluid density. No periappendiceal inflammatory changes. Occluding its orifice, there is a polypoid density which measures approximate 2 cm transversely x 2.3 cm AP x approximately 1.7 cm vertically. It shows Hounsfield unit measurements compatible with soft tissue density. No adjacent significant lymphadenopathy noted.Figure: The sections of the appendix in H&E stain show serrated mucosa throughout the appendix with irregular crypt branching, dilation and serration of crypt bases. These changes are limited to the mucosa with no invasion into the submucosa.