Separating the Wheat From the Chaff: Identifying Sessile Serrated Adenomas Among Polyps Previously Read as Hyperplastic

Abstract

Introduction: Sessile serrated adenomas (SSAs) are important colorectal cancer (CRC) precursor lesions. Due to changing pathologic definitions and criteria, patients with SSAs may be misclassified as having hyperplastic polyps (HPs), particularly in older studies. Surrogate definitions of important serrated polyps such as large or proximal HPs are imperfect, as not all these polyps have malignant potential. We sought to estimate the true proportion of proximal and large HPs that are actually SSAs. Methods: Using pooled data from a series of cross-sectional studies of patients undergoing colonoscopic screening between 1998 and 2010 at the University of North Carolina, we identified patients with proximal HPs and HPs ≥5 mm. Polyps were then reviewed by an expert pathologist using established pathological criteria to determine the presence of SSAs. Data on polyp size, location, and synchronous polyps were abstracted from colonoscopy and pathology reports. Results: Among 2,308 patients undergoing colonoscopy, we identified 532 with lesions initially diagnosed as HPs (23%). One hundred seventy-six patients had proximal HPs, and 126 had HPs ≥5 mm. A total of 191 patients (8%) had either large or proximal HPs and were submitted for pathology review. Among these, 78 patients had at least 1 SSA (41%), and 6 had SSAs with cytological dysplasia. Half of SSAs were associated with synchronous conventional adenomas, and 22 patients (28%) had multiple SSAs (range: 2-12); 55% of those with SSAs were male. The proportion of polyps that were SSAs increased slightly over time (SSAs represented 2.8%, 3.2%, and 4.1% of polyps in 1998-2000, 2001-2005, and 2006-2010, respectively). Compared to reviewed polyps that were confirmed to be HPs, SSAs were larger (mean size 6.4 vs. 4.5 mm; p<0.001), more proximally located (83% vs. 69%; p=0.03), and were more commonly associated with a positive family history of CRC (17% vs. 6%; p=0.03). Conclusion: Patients with SSAs represented roughly 40% of those with proximal or large serrated polyps in this study. Predictors of SSAs among this group included larger size, proximal location, and family history of CRC. These data may aid gastroenterologists to risk stratify and assign appropriate surveillance intervals to patients with large or proximal HPs found on colonoscopy.Table 1: Characteristics of Patients With SSAs