[644] Identification of Histologically Unique Adenomas That Arise Predominately in Patients with CIMP-Associated Polyps

RK Pai, A Noffsinger, J Hart. Univ. of Chicago, Chicago, IL

Background: Serrated polyps have now been subdivided into 5 histologic categories some of which (sessile serrated adenomas [SSAs] and traditional serrated adenomas [TSAs]) have evidence of CpG island methylation (CIMP). However, for the most part adenomas continue to be regarded as a single entitity. We have recently shown that patients with one SSA are much more likely to harbor synchronous TSAs and SSAs, suggesting that there is a field defect in the colons of these patients that predisposes to CIMP-associated polyps. As many of these SSA patients also had apparently typical adenomas, we set out to determine if there were subtle morphologic differences that could distinquish between adenomas from SSA patients and those from non-SSA patients.
Design: A search of our pathology database revealed 105 adenomas from 71 pts. harboring at least one SSA. Seventy-nine consecutive adenomas from 36 pts. without SSAs were also identified. None had features sufficient for a diagnosis of traditional serrated adenoma or SSA with dysplasia, and all appeared as typical adenomas at first glance. Two GI pathologists blindly analyzed these polyps according to ten criteria: focal serration, crypt dilatation, cytoplasmic eosinophila, crypt branching, villous architecture, luminal debris, apoptosis, nuclear shape, type of mucin, and intraepithelial lymphocytes.
Results: Adenomas from patients with SSAs were larger (5.4 mm vs. 4mm, p<0.001) and were significantly more likely to exhibit focal serration, crypt dilatation, cytoplasmic eosinophilia, and increased apoptosis as compared to adenomas from non-SSA patients. 22 of the 105 adenomas in SSA patients demonstrated focal serration, dilation, and eosinophilic cytoplasm compared with only 2 adenomas from non-SSA patients. The location of these adenomas is not significantly different from adenomas in non-SSA patients.


Conclusions: A subset of adenomas in SSA patients are histologically distinct from adenomas in non-SSA patients and may arise through the CIMP-pathway. Molecular analysis of these polyps will be necessary to confirm this hypothesis. These results indicate that adenomas may now be divisible into histologic subtypes based on underlying molecular differences.
Category: Gastrointestinal

Tuesday, March 10, 2009 9:00 AM

Platform Session: Section C, Tuesday Morning