[637] Characterization of Adenocarcinomas Arising in Sessile Serrated Polyps/Adenomas

Kanwaljit S Aulakh, Robert M Genta, Richard H Lash. University of Arkansas for Medical Sciences, Little Rock, AR; Caris Life Sciences, Irving, TX

Background: In recent years, the topic of sessile serrated adenomas (SSA) has been the focus of much clinical and translational research. The significance of these lesions hinges on the risk of the development of adenocarcinoma, particularly for patients undergoing active endoscopic surveillance (so-called “interval” cancers). There is a paucity of research for these cancers that arise from SSAs (SSA-CA), primarily due to their rarity and under-recognition. We evaluated 33 biopsies of SSA-CAs in order to provide a detailed morphologic description, as well as review the demographic and endoscopic characteristics of the patients in which these neoplasms arise.
Design: 33 biopsies with both an invasive adenocarcinoma and either an adjoined or separate SSA on the slide were accepted into the study. When the tumor histology was not typical of conventional colorectal carcinomas (C-CRC), MSI related histologic patterns (mucinous, medullary, signet ring) and other distinct histologic patterns (serrated, percolating, microglandular) were used to characterize these lesions and then their percent composition quantified. Host responses such as intratumoral lymphocytosis, dirty necrosis, and neutrophilic infiltrate were also determined to draw further distinction.
Results: 21 of 33 cases were composed to at least some degree of MSI associated and other distinct histologic patterns, not typical for C-CRC. Four cases were composed entirely of patterns not seen in C-CRC, while 12 cases were composed entirely of C-CRC. The serrated pattern was seen in 12 cases and was the most common pattern seen in the study series. Of the host response features, 11 biopsies had a significant intratumoral lymphocytosis, 13 cases had a neutrophilic infiltrate and 28 cases had dirty necrosis. These carcinomas typically arose in polypoid lesions measuring 10 to 20 mm and located in the right colon in all but 5 cases. Twenty six of the patients were female, and the average age was 71 years.
Conclusions: Being a distinct type of adenocarcinoma by virtue of their pathogenesis, SSA-CAs share many morphologic characteristics commonly seen in C-CRCs and MSI associated cancers, as well as the recently described serrated adenocarcinomas. The identification of an SSA within in the same specimen is requisite for the diagnosis of SSA-CAs. A diagnosis of SSA-CA should be strongly suspected in elderly female patients with a right sided polypoid lesion, measuring between 10 and 20 mm, and an invasive adenocarcinoma. In addition, this is the largest case series of SSA-CAs to date.
Category: Gastrointestinal

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 63, Tuesday Afternoon


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