International and inter-observer differences in macroscopic classification of superficial early colorectal cancer.

Background/aims: The aim of this research is to investigate the international and intra-observer differences in the macroscopic classification of early colorectal cancer between Japan and China.

Methodology: Color pictures of 9 cases of early colorectal cancer were distributed to 6 Japanese and 5 Chinese endoscopists. After reviewing the pictures, the doctors made their classificatory diagnoses independently and indicated their findings on which the diagnoses were based.

Results: There was some consistency in the classification of distinctly elevated lesions among all the Japanese and Chinese endoscopists. However, some elevated lesions classified as type II in Japan might be diagnosed as type I by Chinese endoscopists. For superficial lesions consisting of elevation plus central depression, IIa+IIc or IIc+IIa, were classified according to the ratio of elevation and depression. Although international difference is not significant, inter-observer differences still exist in classifying these lesions. In addition, the differences in laterally spreading tumor were mainly due to terminology.

Conclusions: Japanese and Chinese doctors share a lot of similarities in the classification of flat elevated lesions; however, both international and inter-observer differences still exist in the macroscopic classification for early CRC.