Morphologic Subtypes of Dysplastic Colonic Polyps with Emphasis on Those with Clear Cell Change
Matthew Stachler, Robert D Odze. Brigham and Women's Hospital, Boston
Background: Rarely, conventional adenomas (Ad) may show areas of serrated change. Conversely, sessile serrated adenoma/polyp (SSA/P) and traditional serrated adenoma (TSA) may develop dysplasia reminiscent of Ad. Finally, previous authorities have identified clear cell change in Ad, occasionally in a serrated pattern, that has unknown biological significance. The aim of this study was to reclassify a consecutive series of polyps originally diagnosed as Ad in 1995, based on contemporary WHO 2010 polyp criteria, and to evaluate the clinicopathologic and immunohistochemical features of the unusual group of Ad with clear cell change.
Design: 205 consecutive Ad (from 153 patients) diagnosed in 1995 were re-evaluated for the type of polyp [Ad, TSA with dysplasia (TSA-D), SSA/P with dysplasia (SSA/P-D)] based, in part, on evaluation of the background non-dysplastic component, and also for the presence and degree of clear cell (mucinous) change in the polyp (grade 1=<10%, 2=10-90%, 3=>90%). The clinicopathologic features and association with carcinoma upon long term follow up were evaluated. In addition, a subgroup of 35 polyps (7 Ad, 24 Ad with clear cell change, 3 TSA-D, 1 SSA/P-D) were evaluated for DAS1, MUC1, 2, 5AC, 6, CDX, and P53.
Results: Of the 205 consecutive polyps, 2 were reclassified as SSA/P-D (1%), 11 were reclassified as TSA-D (5.4%) and 52 (25.3%) showed at least focal clear cell change [grade 1=24 (11.7%), 2=23 (11.2%), 3=5 (2.4%)]. Ad with any mucinous component showed a similar gender distribution, mean age, anatomic distribution, and shape, to Ad without clear cell change, but were significantly larger in size (0.83 cm vs 0.55 cm, p=0.0005). Ad with clear cell change showed significant decreased DAS1 and MUC6, and significantly increased MUC5, in areas of clear cell change versus areas with no clear cell change. All other immunomarkers were similar. Overall, 7 patients (4.6%) had or developed cancer, 1 who had only clear cell Ad (2%), none with only SSA/PD (0%), none with only TSA (0%), 5 with Ad (3.6%), and 1 with a clear cell Ad, a TSA, and an Ad.
Conclusions: Based on the current WHO polyp classification, about 6% of polyps actually represent dysplastic serrated polyps (mostly TSA-D and a few SSA/PD). Up to 25% of Ad show clear cell change which shows a different immunophenotype from epithelium without clear cell change, but otherwise similar clinicopathologic features and association with cancer. Cancer outcome was similar in all groups, but further studies with larger numbers of patients are needed.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 62, Tuesday Afternoon