Non-polypoid colorectal neoplasias: A multicentric study

A total of 781 non-polypoid colorectal neoplasias harvested at 4 main Hospi tals in Tokyo, Japan (n=420) and at 4 different time-intervals at the Karol inska Hospital, Stockholm, Sweden (n=361) were reviewed. By applying strict histologic definitions, the lesions were classified into adenomas with low grade dysplasia (LGD), with high grade dysplasia (HGD), intramucosal carci nomas (IMC) or submucosal carcinomas (SMC). Of the non-polypoid neoplastic lesions reviewed in Sweden, 82.8% (n=299) had LGD. In Japanese patients onl y 42.6% (n=179) had LGD (p less than or equal to 0.001). On the other hand, as many as 42.4% (n=178) of the non-polypoid lesions in Japanese patients had HGD, but only 14.1% (n=51) of those in Swedish patients (pl 0.001). Whe reas 15.0% (n=63) of the non-polypoid neoplasias seen in Japan were IMC ol SMC, only 3.0% (n = 11) of those seen in Sweden were IMC or SMC (p less tha n or equal to 0.001). The cause(s) for these differences remains unclear. I n Japan, however, a marked increased incidence of colonic cancer has been r ecorded in later years. Whether the "catching up phenomenon" by the Japanes e with western colonic cancer incidence includes increased histologic aggre ssiveness of non-polypoid neoplastic polyps -as found in this survey- remai ns to be elucidated.