A comprehensive study of nondysplastic and dysplastic serrated polyps of the vermiform appendix.
Serrated colorectal polyps often show DNA hypermethylation and/or BRAF mutations and have been implicated in the "serrated neoplastic pathway." Although similar lesions occur in the appendix, they have never been systematically investigated. We evaluated a study group of 56 serrated polyps, a control group of 17 mucinous cystadenomas, and 4 adenocarcinomas with adjacent serrated polyps of the appendix to better understand their pathogenesis. The study cases were classified as nondysplastic or dysplastic serrated polyps and evaluated for MLH-1, MSH-2, MGMT, beta-catenin, p53, and Ki-67 expression, BRAF and KRAS mutations, and microsatellite instability. Serrated polyps usually occurred in older adults with no sex predilection. Most (59%) lacked dysplasia, but all showed similar molecular features, regardless of the degree of dysplasia present. Decreased MLH-1 (50%, P<0.001) and/or MGMT (59%, P<0.001) expression and BRAF (29%, P=0.007) mutations were significantly more common in serrated polyps, but BRAF mutations were detected in a minority of the extracted DNA in 15/16 cases. Of the 28 cases with decreased MLH-1 expression, none showed high-frequency microsatellite instability. Loss of MLH-1 (25%) or MGMT (50%) expression and BRAF or KRAS mutations (50%) were inconsistently present in adenocarcinomas and were not identified in combination in any cases. We conclude that molecular features of the "serrated neoplastic pathway" are present with similar frequencies among dysplastic and nondysplastic serrated appendiceal polyps and are not highly prevalent in adjacent carcinomas. These features, including BRAF mutations, may be more closely related to a serrated morphology in appendiceal polyps rather than biologically important changes.
Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10021, USA. rhy2001@med.cornell.edu
Rhonda K
RK
Yantiss
Andrea
A
Panczykowski
Joseph
J
Misdraji
Hejin P
HP
Hahn
Robert D
RD
Odze
Hanna
H
Rennert
Yao-Tseng
YT
Chen
D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis; D000230:Adenocarcinoma / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D018256:Adenomatous Polyps / Q000737:chemistry / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001065:Appendix / Q000737:chemistry / Q000473:pathology*; D002430:Cecal Neoplasms / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D018291:Cystadenoma, Mucinous / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D015254:DNA Modification Methylases / Q000032:analysis; D045643:DNA Repair Enzymes / Q000032:analysis; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009092:Mucous Membrane / Q000473:pathology; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000032:analysis; D009154:Mutation; D009361:Neoplasm Invasiveness; D009687:Nuclear Proteins / Q000032:analysis; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D025521:Tumor Suppressor Proteins / Q000032:analysis; D051176:beta Catenin / Q000032:analysis / Q000235:genetics; D018631:ras Proteins / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; C495270:CTNNB1 protein, human; C117307:KRAS protein, human; D019394:Ki-67 Antigen; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051176:beta Catenin; D015254:DNA Modification Methylases; C515491:MGMT protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D045643:DNA Repair Enzymes