endoscopic characterization of a diminutive sporadic BRAF mutant traditional serrated adenoma arising from a sessile serrated legion. My name is Ammar Kheir. My co-author is Priti Joshi and we have no disclosures. TSAs are rare serrated polyps that can cause aggressive colorectal cancer. The natural history is not fully understood, but molecular studies divide them into KRAS mutated TSAs and BRAF mutated TSAs that are believed to arise from sessile serrated legions, but endoscopic evidence is lacking. A 29 year old female underwent a diagnostic colonoscopy. A single sporadic 5 millimeter in size polyp was found in the distal transverse colon. The polyp had two components, which was classified under the Paris classification as Paris 2a plus 2b. Optical diagnosis was consistent with traditional serrated adenoma arising from a sessile serrated legion. We used an adult colonoscope and optical diagnosis was performed using high-definition white light and narrowband imaging. The polyp was resected using unblock endoscopic mucosal resection and the resected polyp was retrieved using a retrieval net to guard against polyp fragmentation. The specimen was pinned to prevent curling and to facilitate accurate histologic assessment. A single 5 millimeter polyp in the distal transverse colon was found. The polyp had two component appearances with a 3 millimeter protuberant Paris classification 2a with red color and villiform-like morphology under high-definition white light with NBI being more consistent as an atypical NAS classification type 2 with this plastic morphology that endoscopically was predicted to be traditional serrated adenoma. However, the polyp had an abrupt transition into a subtle 2 millimeter flat component on the right side with Paris classification 2b with pale color or white color serrated looking legion with NBI being more consistent with NAS classification type 1 with indistinctive borders irregular shape and dark spots inside the crypts that was predicted to be a sessile serrated legion. The final diagnosis was a TSA arising from sessile serrated legion hence unblock EMR was performed after submucosal injection with methylene blue and saline with epinephrine at a final concentration of 1 in 100,000. After submucosal injection the legion was better delineated and as you can see the continuous and abrupt transition between the flat component sessile serrated legion and the protuberant dysplastic component of the TSA. A 15 millimeter stiff snare was used to ensure an unblocked resection with good margins of normal tissue. Controlled snare closure is being performed to prevent against snare slippage and the polar was successfully grasped The specimen was retrieved using a retrieval net to prevent specimen fragmentation and optimize histologic assessment. Thermal ablation was performed to the margins and the defect of the EMR to prevent against invisible neoplasia that may recur on surveillance. the EMR defect was closed using through the scope clips. and EMR is completed. The polyp was pinned into a firm surface using needles to optimize pathologic assessment. The histologic assessment under low power mode showed a villiform dysplastic architecture consistent with traditional serrated adenoma, as seen on the left green box. And on the right green box, you can see the architecture of a serrated lesion, which is consistent with a sessile serrated lesion. Under high power mode, the TSA component showed dysplastic features with slit-like serrations, as indicated by the green arrows, and ectopic creep formations, as indicated by the green circles. For the sessile serrated lesion component, there were dilated creeps at the bases, as indicated by the green arrow. BRAF immune staining showed increased cytoplasmic staining in the flat portion of the polyp, corresponding histologically to sessile serrated lesion, as well as in the protuberant portion of the polyp, corresponding histologically to traditional serrated adenoma. The clinical implications of this case include the description of endoscopic features of BRAF mutant traditional serrated adenoma when caught in the act arising from sessile serrated lesion. Furthermore, the endoscopic prediction of this lesion facilitated the prioritization of immediate removal of this diminutive lesion with an enhanced resection method using on-block EMR. In addition to optimizing the specimen quality to facilitate accurate pathologic assessment by pinning the specimen and performing BRAF mutation testing. So in conclusion, BRAF mutant traditional serrated adenomas arising from sessile serrated lesions appear to occur very early within the serrated pathway compared to sessile serrated lesions with cytological dysplasia. We described the endoscopic features of diminutive BRAF mutant TSAs arising from SSLs. An optical diagnosis is an important technique during routine colonoscopy, even for diminutive lesions.

endoscopic characterization

rare type of polyp

traditional serrated adenoma

sessile serrated lesion

optical diagnosis