Flat adenoma-carcinoma sequence with high-malignancy potential as demonstrated by CD10 and β-catenin expression: A different pathway from the polypoid adenoma-carcinoma sequence

Aims: CD10+ colorectal carcinomas have a high risk of giving rise to liver metastasis. The aim was to examine phenotypic expression in colorectal neoplasia and to elucidate changes in such expression through the adenoma-carcinoma sequence. Methods and results: We examined the expression of various proteins immunohistochemically in 111 flat [non-polypoid growth (NPG)] colorectal neoplasms, categorized into 28 low-grade (NPG-LGN), 44 high-grades (NPG-HGN) and 39 cases of invasive neoplasia (NPG-IN), as well as in 96 polypoid [polypoid growth (PG)] neoplasms, categorized into 26 PG-LGN, 39 PG-HGN and 31 PG-IN according to the Vienna classification. CD10 was more frequently expressed in NPG than in PG neoplasia. MUC2 and MUC5AC were more frequently expressed in PG than in NPG neoplasias. Nuclear β-catenin was more frequently expressed in NPG-LGN than in PG-LGN. No difference in p53 expression was found between NPG and PG neoplasia. Conclusions: From the viewpoint of the expression of CD10 and β-catenin, it would appear that NPG-LGN differs significantly from PG-LGN, thereby indicating that NPG-LGN is a precursor of CD10+ carcinoma. It is important to ensure that NPG neoplasia is not overlooked if cases of CD10+ carcinoma are to be detected at an early stage.