Histopathology of early colorectal cancer

The histopathologic spectrum of early colorectal cancer (ECC) is compared f rom the Western and Japanese perspective. In the West, most ECC presents as a malignant adenoma, whereas superficial ECC with no adenomatous component is well described in the Japanese literature. Furthermore, superficial ECC is thought to progress rapidly and disseminate early. The discrepant viewp oints are considered in the light of different approaches to histopathologi c interpretation. Lesions reported by Japanese pathologists as superficial carcinomas limited to the mucosa are diagnosed as flat adenomas in the West . In one Japanese series only 4 of 218 (1.8%) flat or small sessile neoplas ms removed by endoscopic mucosal resection were associated with submucosal invasion by carcinoma. Therefore superficial ECC with submucosal spread is uncommon. Most ECC in hereditary nonpolyposis colorectal cancer evolves thr ough the adenoma-carcinoma pathway (including flat adenoma). However, adeno ma removal in the context of population-based screening programs has not lo wered the incidence of colorectal cancer; flat colorectal neoplasia may be important in clinical practice.