Mismatch repair protein expression in Amsterdam II criteria-positive patients in Taiwan

Background: Hereditary non‐polyposis colorectal cancer (HNPCC) is characterized genetically by germline mutations in DNA mismatch repair (MMR) genes. Immunohistochemistry (IHC) has high sensitivity and specificity for identifying MMR‐deficient tumours. This study investigated the clinical presentations and frequency of HNPCC in Taiwan by combined Amsterdam II criteria (AC‐II) and IHC. Methods: In 1995–2003, 7108 patients with primary colorectal cancer registered in Chang Gung Memorial Hospital's Colorectal Cancer Registry were screened using AC‐II. Tumour specimens were analysed for MMR protein expression by IHC, and relevant clinicopathological details were documented. Results: Some 83 patients fulfilled the AC‐II. Clinicopathologically, 43 patients (52 per cent) had proximal tumours, ten (12 per cent) had poorly differentiated cancers, 17 (20 per cent) had mucinous adenocarcinoma and 51 (61 per cent) had stage I–II tumours. Seventeen patients developed second primary colonic and extracolonic cancers over a mean 7·2‐year follow‐up. Immunohistochemically, 58 patients were MMR protein deficient. They had a significantly earlier age of onset (P < 0·001), more proximal tumour location (P = 0·002), less advanced tumour stage (P = 0·008) and more second primary cancers (P = 0·017) compared with MMR‐competent patients. Conclusion: These data show significant differences in clinical features between MMR protein‐deficient and MMR competent subgroups. Copyright © 2007 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. Approximately one per cent of colorectal cancers