Demographic and pathological characteristics of serrated polyps of colorectum.
OBJECTIVE
To characterize a series of colorectal polyps, focusing on the clinicopathological features of serrated adenoma (SA), mixed polyp (MP) and the recently recognized sessile serrated adenoma (SSA).


RESULTS
Eight hundred and ninety-one conventional adenomas (AD), 298 hyperplastic polyps (HP), 27 SSA, 10 MP and 24 traditional SA were obtained from patients during colonoscopic examination. SSA were more likely to be proximally located than other polyps. All SA, MP and SSA and a randomly selected subset of HP (n = 61) and ADs (n = 93) were assessed for expression of mucin, MLH1, MGMT, and Ki67. SSA expressed more MUC5AC than either HP or SA. Loss of MLH1 was not observed in any serrated polyps and in only one AD. Loss of MGMT occurred in 13% of AD, and showed no correlation with histological type, size or location. Loss of MGMT occurred in 24% of SSA, MP and SA (combined), and was more frequent in proximal lesions and larger lesions. SSA had a higher proliferative index than HP. In MP, the proliferative index of the non-dysplastic component was closer to HP than SSA, while the dysplastic component was intermediate between SA and AD.


CONCLUSIONS
SSA differ from other serrated polyps of colorectum in terms of location, morphology and immunophenotype.
Higuchi
T
T
Department of Pathology, McGill University, Montreal, Quebec, Canada.
Sugihara
K
K
Jass
J R
JR
D000236:Adenoma / Q000378:metabolism / Q000473:pathology*; D000368:Aged; D003111:Colonic Polyps / Q000378:metabolism / Q000473:pathology*; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis; D008297:Male; D008875:Middle Aged; D055271:Mucin 5AC; D055262:Mucin-2; D009077:Mucins / Q000032:analysis
D019394:Ki-67 Antigen; C524625:MUC2 protein, human; C524678:MUC5AC protein, human; D055271:Mucin 5AC; D055262:Mucin-2; D009077:Mucins