{"type":"rich","version":"1.0","provider_name":"Transistor","provider_url":"https://transistor.fm","author_name":"Board Pearls","title":"Chapter 30, Ep 5 of 5: Serrated Pathway, Lynch, and Special Populations","html":"","width":"100%","height":180,"duration":976,"description":"Episode five closes the chapter on the other half of why colonoscopy quality matters, the serrated pathway where missed right-sided lesions become interval cancer. Sessile serrated lesions run through BRAF V600E, CIMP-high hypermethylation, MLH1 silencing, and microsatellite instability, which is why sessile serrated lesion detection rate is its own quality metric. That molecular route drives the Lynch reflex tree: mismatch repair immunohistochemistry, then BRAF and MLH1 methylation to triage sporadic disease, with the other loss patterns going straight to germline testing because sporadic biology cannot explain them. The special populations then bend the standard algorithm one mechanism at a time, as the kidneys forbid phosphate, the liver forbids morphine, the fetus forbids first-trimester benzodiazepines, and the IBD colon demands chromoendoscopy.\n \nTopics covered\n\nSerrated pathway molecular biology\nLynch universal tumor screening\nBRAF V600E as sporadic discriminator\nMMR loss patterns and germline testing\nSerrated polyposis syndrome criteria\nPhysiology-driven special populations\nPregnancy, cirrhosis, and ESRD colonoscopy\nIBD chromoendoscopy surveillance\nPeriprocedural antithrombotic management\n \n \nKey decisions\n\nCombined MLH1 and PMS2 loss on immunohistochemistry reflexes to BRAF V600E testing, and a positive result triages the patient away from germline testing because the cancer is sporadic CIMP-pathway disease.\nA negative BRAF result reflexes to MLH1 promoter methylation testing, and only when both BRAF and methylation are negative does germline sequencing for Lynch syndrome become indicated.\nIsolated loss of MSH2, MSH6, or PMS2 goes straight to germline testing without BRAF or methylation, because sporadic methylation acts on MLH1 specifically and cannot explain those losses.\nThe WHO twenty nineteen serrated polyposis definition requires either five or more serrated polyps proximal to the rectum all at least five millimeters with two over ten, or more than...","thumbnail_url":"https://img.transistorcdn.com/-FuAdDBcPDLhEoUmroZKtOBRvuBn_FHPpYlh41hOnU4/rs:fill:0:0:1/w:400/h:400/q:60/mb:500000/aHR0cHM6Ly9pbWct/dXBsb2FkLXByb2R1/Y3Rpb24udHJhbnNp/c3Rvci5mbS9iNzlh/ZTU4Y2MzNWExMjQ5/MjA5OWMwMmI3ZTk5/NGFiZS5wbmc.webp","thumbnail_width":300,"thumbnail_height":300}