| [ Summary ] |
In order to clarify the morphogenetic characteristics of depressed colorectal cancers, we histologically classified NPG structures into two types, first NPG structures with flat margins (NPG-F) type and secondly NPG structures with depressed margins (NPG-D) type. There were 42 submucosal and 61 advanced cancers, of less than 3cm in size. We classified these 103 lesions into three types ; PG (48), NPG-F (36), and NPG-D (19). We analyzed the relationship between morphogenesis and K-ras codon12 point mutations of these types. The frequency of K-ras codon12 point mutation in NPG-D, smaller than 2cm was 0%, significantly lower than in PG 43% (p=0.0107). This evidence might suggest that NPG-D less than 2cm in size has a different pathogenetic pathway than the "adenoma-carcinoma sequence". However, no difference was seen in K-ras codon12 point mutations between PG (44%) and NPG-D (40%) in advanced cancers of 2 to 3cm in size. It may imply a possibility that during the progression to more advanced cancers, PG and NPG-D would experience shift in numbers. Therefore, it is suggested that the classifications of PG and NPG-D would be applicable in small advanced cancers of 2cm or less in size. |