Combination analysis of genetic alterations and cell proliferation in small intestinal carcinomas.

We analyzed K-ras and p53 mutations, microsatellite instability (MSI), and loss of heterozygosity (LOH) using the polymerase chain reaction (PCR) methods, as well as p53 expression and the Ki-67 labeling index (LI) using immunohistochemistry in 10 duodenal and 10 jejunal/ileal carcinomas. K-ras mutations were detected in two duodenal (20%) and three jejunal/ileal (30%) carcinomas and p53 mutations in one (10%) and three (30%), respectively. LOH of 17p was detected in two duodenal (20%) and two jejunal/ileal (20%) carcinomas and p53 expression in four duodenal (40%) and four jejunal/ileal (40%). One duodenal (10%) and two jejunal/ileal (20%) carcinomas demonstrated MSI. LOH of APC was detected in three jejunal/ileal (30%), but none of the duodenal carcinomas. The Ki-67 LI was 44% in duodenal and 52.6% in jejunal/ileal carcinomas. A subset of small intestinal carcinomas showed involvement of K-ras and p53 mutations, LOH of APC, and MSI. A difference was also apparent for LOH of APC between duodenal and jejunal/ileal carcinomas.