Abstract
Focusing on the clinical features of hereditary nonpolyposis colorectal cancer（HNPCC） in Japan, we have analyzed 311 colorectal cancer（CRC）cases in 62 HNPCC families conform to Amsterdam criteria. Furthermore we compared the findings with those in 346 CRC cases without family history of cancer as controls. Results revealed that the average age of cancer onset in HNPCC was 43.1 years; whereas it was 62.6 years in the controls（CRCs without cancer family history）, and that the rate of patients whose cancer was diagnosed under the age of 50 was 74.7% and 14.8% respectively. As to site, it was found that the colorectal cancer had occurred in the proximal colon of 38.4% of HNPCC patients and in 27.9% of the controls, and that the frequency of rectal cancer was 27.4% and 50.3%, respectively. Also, synchronous or metachronous multiple cancers including multiple colorectal cancers were found to have occurred in 31.9% of HNPCC patients and in 4.8% of the controls. Thus, the clinical features of HNPCC are characterized by an early age of onset, a predominant siting in the proximal colon, and a high incidence of multiple primary neoplasms including multiple colorectal cancers.
