Based on the patients's age of 39 (less than 50 years old), immunohistochemical staining for the major DNA mismatch-repair (MMR) proteins MLH1 and MSH2 was performed to exclude the possiblity ofan inherited form of intestinal neoplasia, hereditary non-polyposis colorectal cancer (HNPCC). Here, MLH1 is linked to hereditary nonpolyposis colon cancer.