title: Microsatellite-unstable mucinous colorectal carcinoma occurring in the elderly: comparison with medullary type poorly differentiated adenocarcinoma.
abstract: Mucinous carcinoma and poorly differentiated adenocarcinoma of the large intestine have a high frequency of microsatellite instability, and their occurrence increases gradually with age. To elucidate the clinicopathological and immunohistochemical features of microsatellite-unstable mucinous carcinoma and compare the tumor with medullary type poorly differentiated adenocarcinoma, the clinicopathological status and expression of mucin core and hMLH1 proteins were studied in 15 microsatellite-unstable and 20 microsatellite-stable mucinous colorectal carcinomas occurring in elderly patients, and compared with 23 cases of medullary type poorly differentiated adenocarcinoma in which 21 cases were microsatellite-unstable. Thirteen (87%) of 15 microsatellite-unstable carcinomas exhibited absent hMLH1 expression compared with three (15%) of 20 microsatellite-stable carcinomas (P < 0.01). The proportion (87%) of positive MUC5AC expression in microsatellite-unstable mucinous carcinoma was significantly higher than that (45%) in microsatellite-stable mucinous carcinoma (P = 0.01). Compared with microsatellite-stable mucinous carcinoma, microsatellite-unstable mucinous carcinomas were significantly associated with a proximal location, intra- and peritumoral inflammatory cell infiltration, frequent MUC5AC expression, a low incidence of lymph node metastasis and absent hMLH1 protein expression, which is not different to medullary type poorly differentiated adenocarcinoma except for MUC2 expression and age-related occurrence. These results suggest that microsatellite-unstable mucinous carcinoma occurring in the elderly shares clinicopathological and molecular features with medullary type poorly differentiated adenocarcinoma and that microsatellite instability with absent hMLH1 expression plays an important role in the development of these two carcinomas.
authors.affiliation: Department of Pathology, Tokyo Metropolitan Geriatric Hospital, Sakaecho, Tokyo, Japan. arai@tmig.or.jp
authors.forename: Tomio
authors.initials: T
authors.lastname: Arai
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kasahara
authors.forename: Motoji
authors.initials: M
authors.lastname: Sawabe
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kanazawa
authors.forename: Kojiro
authors.initials: K
authors.lastname: Kuroiwa
authors.forename: Naoko
authors.initials: N
authors.lastname: Honma
authors.forename: Junko
authors.initials: J
authors.lastname: Aida
authors.forename: Kaiyo
authors.initials: K
authors.lastname: Takubo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D002288:Adenocarcinoma, Mucinous / Q000235:genetics* / Q000473:pathology; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics* / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D055271:Mucin 5AC; D009077:Mucins / Q000235:genetics; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; C524678:MUC5AC protein, human; D055271:Mucin 5AC; D009077:Mucins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1