Abstract
We investigated the growth and progression of colorectal carcinomas by histological findings, K-ras point mutation and immunohistochemical studies of P53 in advanced colorectal carcinomas of less than 20mm in diameter. Thirty-one cases of advanced colorectal carcinomas of less than 20mm were obtained from surgically resected specimens. P53 was examined by immunohistochemical staining using microwave and LSAB method. We used antibody NCL-P53-CM1. DNA was extracted from formalin-fixed and paraffin-embedded sections. A mutation of colon 12 of K-ras gene was detected by polymerase chain reaction (PCR) and dot blot hybridization. They were classified into three groups ; polypoid growth (PG), non-polypoid growth (NPG) and intermediate growth by intramucosal growth type. The average age was 60. The locations were ascending colon: 1, transverse colon : 4, descending colon: 7, sigmoid colon : 15, rectum : 4. All samples were well differentiated adenocarcinoma, except two with poorly differentiated type. Histological depth was mp :19, and deeper: 12. K-yas mutation was found in PG carcinoma : 55%, NPG carcinoma : 0%, intermediate type : 36% by 15 to 20mm in diameter. However we found no mutation of K-ras genes in PG and NPG of less than 15mm in diameter. In contrast, there was no difference in immunohistochemical staining of P53 between PG or NPG. Based on these results, it is concluded that early carcinomas positive for P53 and negative for K-yas mutation will grow into advanced carcinoma of less than 20mm in diameter, and its tendency is clearer in most of smaller colorectal carcinomas.
