Hereditary nonpolyposis colon cancer (HNPCC) accounts for about 5% of all colorectal cancer. Mutations in the DNA mismatch repair genes (hMLH1, hMSH2 and PMS families) are responsible to HNPCC. To study the characteristics and optimal treatment modality of Korean HNPCC patients, we analysed the 29 HNPCC families registered in the Korean Hereditary Colorectal Cancer Registry. The control group consisted of 791 colorectal cancer patients treated in Seoul National University Hospital between 1991 and 1994. Twenty-nine HNPCC families included 316 (79 males and 37 females) colorectal cancer patients. Following findings were significantly different from those of control group. ① Their average age at diagnosis was younger (44 years) than that of control group (56 years). ② Thirty-nine percent of colorectal cancer were located proximal to splenic flexure compared to 24% of control group. ③ Fifty percent of cancers located in sigmoid colon or rectum, but in control group 73% of cancers located in those area. In Western series, however, only 23.3% of cancers located in the sigmoid colon or rectum.
Operative and pathologic records were available from 45 HNPCC patients. Forty-four percent of those 45 HNPCC patients had multiple colorectal cancers including polyps. Thirty-eight percent of HNPCC patients had the tumors in both sides of the large bowel. Forty-five patients received 52 operations, but only 13 cases (25 % ) were total or subtotal colectomy. Endometrial cancer and stomach cancer were the most frequent extracolonic cancers in HNPCC. HNPCC should be suspected in colorectal cancer patients with early age of onset and proximal colon involvement, or multiple colorectal cancers. We confirmed that the extent of the resection for HNPCC patients should be more than subtotal colectomy. Screening for endometrial and stomach cancer was necessary in families with those cancers. Especially woman with HNPCC should be considered hysterectomy and bilateral salpingo-oophorectomy at the time of colectomy.