Genetic counseling and testing in families with hereditary nonpolyposis colorectal cancer

BACKGROUND: Genetic testing to refine cancer risk is available. However, little is known about factors affecting the uptake of testing for the most common hereditary colon cancer, hereditary nonpolyposis colorectal cancer. This study investigated attitudes, intentions, and uptake of genetic testing within newly identified families with hereditary nonpolyposis colorectal cancer. METHODS: Cohort study conducted at the National Institutes of Health between April 15, 1996, and November 20, 1999. Data were collected through questionnaires before semistructured education sessions, individual counseling sessions, and the offer of genetic testing. RESULTS: Of the 111 eligible first-degree relatives, 51% chose to participate in education and individual counseling sessions. Participation was associated with greater numbers of first-degree relatives with cancer; no association was found between participation and personal history of cancer. Before education and individual counseling sessions, 64% of participants had heard little about genetic testing for cancers; however, most (97%) stated intentions to pursue testing. Fifty-one percent identified learning about their children's risks as the most important reason to consider testing. Thirty-nine percent identified the potential effect on their health insurance as the most important reason to not undergo testing. Of the 111 eligible first-degree relatives, 51% chose to undergo genetic testing. Participants' intentions to pursue genetic testing were significantly affected by concerns regarding the ability to handle the emotional aspects of testing and the psychosocial effect on family members. CONCLUSIONS: Genetic counseling and testing offers the potential to focus cancer screening resources in individuals truly at increased risk, thereby reducing mortality and morbidity. Fears of discrimination and concerns about psychological and psychosocial issues may present barriers to the use of current cancer prevention strategies, including genetic counseling and testing.     

Genetic testing in hereditary colorectal cancer: indications and procedures

Approximately 25% of colorectal cancers occur in younger individuals or those with a personal or family history of the disease, suggesting a heritable susceptibility. The minority of these cases are accounted for by one of the well-described hereditary colorectal cancer syndromes, familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). The recent identification and cloning of the genes responsible for FAP and HNPCC, along with other colon cancer susceptibility genes, has led to the wide-spread availability of genetic testing for hereditary colorectal cancer. Genetic testing raises clinical, ethical, legal, and psychosocial questions that must urgently be discussed. This review highlights areas of knowledge and uncertainty about genetic predisposition testing for colorectal cancer and provides clinicians with practical recommendations regarding the proper indications and procedures for this testing.     

Awareness of genetic testing for colorectal cancer predisposition among specialists in gastroenterology

OBJECTIVES: Adult gastroenterologists practicing in New York State were surveyed to determine their practice with regard to identifying family histories consistent with inherited forms of colorectal cancer, and to assess their awareness of cancer genetic counseling and molecular genetic testing for familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). METHODS: A closed-ended questionnaire was mailed to 815 gastroenterologists identified through the membership Directory of the American Gastroenterological Association (1998). Two mailings resulted in a response rate of 35%. RESULTS: In all, 99% of the gastroenterologists obtained a family history from their patients, and 95% were aware of cancer genetic counseling. However, only 51% would routinely refer patients for genetic counseling before providing cancer predisposition testing. In addition, only 52% were aware of the availability of genetic tests for FAP and 34% for HNPCC. Presented with a family history consistent with HNPCC, 79% could identify the syndrome, 26% recommended genetic counseling for the consultand, and 16% advised appropriate screening, according to current recommendations. CONCLUSIONS: The majority of gastroenterologists do obtain a family history on their patients. However, there is a need for physician education regarding the recognition of pedigrees consistent with inherited colorectal cancer, the genetic counseling process, and the availability of mutation testing for FAP and HNPCC.     

The hereditary nonpolyposis colorectal cancer syndrome: genetics and clinical implications

Basic studies of DNA replication and repair have provided surprising and pivotal insights into a novel pathway of tumorigenesis. Defects in the DNA mismatch repair process dramatically increase the risk for specific types of cancer because of instability in microsatellite DNA sequences. A germline mutation in either the hMSH2 or hMLH1 mismatch repair gene results in the hereditary nonpolyposis colorectal cancer (HNPCC), or Lynch, syndrome. The lifetime risk for colon cancer is 80% in affected persons, and an aggressive cancer surveillance program is essential not only for these individuals but also for at-risk family members. The diagnosis of HNPCC can be made by fulfillment of the Amsterdam clinical criteria or through genetic testing for germline mutations in hMSH2 or hMLH1. Genetic testing is particularly useful in families with atypical clinical features and also for cancer risk assessment within an established HNPCC kindred. Microsatellite instability (MSI) of DNA is a hallmark feature of HNPCC-associated tumors, and as many as 15% of cases of sporadic colorectal cancer also display MSI. The biological behavior of colorectal tumors with MSI is distinctive; the most intriguing feature is their favorable natural history. The study of HNPCC has provided an example of the powerful interplay between molecular genetics and clinical care.     

Colorectal cancer and the Muir-Torre syndrome in a Gypsy family: a review

OBJECTIVES: The Muir-Torre syndrome (MTS) is characterized by an autosomal dominant predilection to sebaceous adenomas, sebaceous carcinomas, and multiple keratoacanthomas, in concert with the cancer phenotype of hereditary nonpolyposis colorectal cancer (HNPCC). Proof that patients showing a familial aggregation of MTS's cutaneous signs in combination with a specific pattern of visceral cancers which are consonant with an HNPCC diagnosis has been buttressed by the discovery of hMSH2 and hMLH1 germ-line mutations in such families. Our purpose in this investigation was to determine the germ-line mutation in a Gypsy family with MTS in concert with HNPCC cancer features, and to provide genetic counseling. An added objective for this paper is to review the literature on MTS. METHODS: We describe a Gypsy family with MTS in concert with HNPCC cancer features, as well as the molecular genetic and genetic counseling procedures used in the interest of improved compliance with cancer control recommendations. We review the clinical phenotype, natural history, and molecular genetics involved in the MTS variant HNPCC. RESULTS: An hMSH2 germ-line mutation was identified as the culprit germ-line mutation in this family. CONCLUSIONS: The presence of the hMSH2 germ-line mutation in this family provides powerful predictability of colorectal and other HNPCC integral cancers. The gastroenterologist must assume an important role in the diagnosis and management of MTS.     

Genetic counseling and interpretation of genetic tests in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer

PURPOSE: Genetic counseling and interpreting genetic test results can be complex. Moreover, without knowing the limitations of the methods used and the lifetime probability of developing cancer in individuals who carry a gene that predisposes to cancer, misinterpretation may lead to false assurance. The purpose of this review is to discuss how genetic counseling will benefit patients and their family, the genetic tests available for hereditary colorectal cancer syndromes, and the interpretation of results. METHODS: Current literature was reviewed and our clinical and research experiences were incorporated. RESULTS: This review serves as a guide to enable various health care providers to better counsel patients in their quest for advice on prevention, early detection, and surveillance for colorectal cancer. Notable topics of discussion are who should undergo genetic counseling and consider testing and how the interpretation of test results can be misleading; for example, understanding the difference between a no mutation detectedvs. a negative test result. CONCLUSIONS: Genetic counseling is of paramount importance for patients to fully understand the limitations of genetic testing and will aid in the management of patients who are susceptible to colorectal cancer.     

Hereditary ovarian cancer

At least 10% of ovarian tumors are hereditary and associated with highly penetrant, autosomal, dominant genetic predisposition. Three clinical manifestations of hereditary ovarian cancer have been identified: site-specific ovarian cancer, hereditary breast and/or ovarian cancer (HBOC) and hereditary non-polyposis colorectal cancer (HNPCC) syndromes. BRCA germline mutations account for more than 90% of all hereditary epithelial ovarian tumors whereas most of the remaining 10% are caused by MLH1 and MSH2 mutations, which are susceptibility genes of HNPCC. Genetic testing is available for each of the three hereditary syndromes above mentioned. The recommendations for OC surveillance in high-risk women having a strong family history or BRCA mutation carriers include transvaginal pelvic ultrasound with color Doppler and serum CA125 every 6 months. Bilateral salpingo-oophorectomy appears to be effective to reduce the risk of ovarian cancer in BRCA mutation carriers. Hysterosalpingo-oophorectomy should be considered in HNPCC women who undergo surgery for colorectal carcinoma.     

Natural history of colorectal cancer in hereditary nonpolyposis colorectal cancer (Lynch syndromes I and II)

Approximately 5 to 6 percent of the total colorectal cancer burden is accounted for by hereditary nonpolyposis colorectal cancer (HNPCC). Because clinical premonitory signs such as those seen in familial polyposis coli (FPC) are lacking, the clinician must recognize clinical findings and family history typical of HNPCC. The authors have described colorectal cancer expression from a survey of ten HNPCC kindreds. Kindred members with colorectal cancer differed significantly (P<.05) from patients with sporadic colorectal cancer: 1) mean age of initial colon cancer diagnosis was 44.6 years; 2) 72.3 percent of first colon cancers were located in the right colon, and only 25 percent were in the sigmoid colon and rectum; 3) 18.1 percent had synchronous colon cancers; and 4) 24.2 percent developed metachronous colon cancer, with a risk for metachronous lesions in ten years of 40 percent. Affecteds and their first-degree relatives should undergo early intensive education and surveillance. In families with an early age of onset, colonoscopy should begin at age 25, and biannually thereafter, with fecal occult blood testing of the stool semiannually. Third-party carriers must become more responsive to the costly surveillance measures required for these otherwise healthy patients. Supported by NIH Grants No. 5 RO1 CA41371-01 and 1 RO1 CA42705-01.     

Hereditary colorectal cancer: clinical consequences of predictive molecular testing

The continuing increase in knowledge about the genetic basis of carcinogenesis has led to diverse efforts to exploit this knowledge clinically, primarily in the form of predictive genetic testing. In conjunction with family history, gene tests are intended to improve individual cancer risk assessment. The objectives of predictive molecular testing are to identify the disease-causing germline mutation in an index person who has already developed the disease and to distinguish asymptomatic mutation carriers from non-mutation carriers within a given cancer-prone family. At present, genetic testing for colorectal cancer risk, primarily in form of DNA sequencing, is applied in familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). In these inherited colorectal tumor syndromes determining the genetic status may result in an individually tailored surveillance program and prophylactic treatment. The implications of genetic testing for the clinical management of disease, both of mutation and non-mutation carriers, in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer families are discussed. Accepted: 9 September 1999     

Microsatellite instability—a useful diagnostic tool to select patients at high risk for hereditary non-polyposis colorectal cancer: a study in different groups of patients with colorectal cancer

BACKGROUND: Clinical diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) is based on a typical family history. As molecular genetic testing is predominantly restricted to these families, gene carriers not meeting the clinical criteria may be missed. AIMS: To examine the value of microsatellite instability (MSI) as a tool to increase the likelihood for uncovering a mismatch repair germline mutation in patients with colorectal cancer and to identify a genotype-phenotype relation in families with verified mutations. METHODS: Systematic search for germline mutations (hMSH2 and hMLH1 genes) was performed in 96 patients: 57 fulfilled the Amsterdam criteria (group 1) and 12 the looser HNPCC criteria (group 2). Seventeen patients showed familial clustering of cancers (group 3) and 10 patients under 50 years had sporadic cancer (group 4), the latter of whom all exhibited MSI+ tumours. RESULTS: A similar proportion of germline mutations was found in patients who fulfilled the clinical criteria of HNPCC and had MSI+ tumours (groups 1 and 2; 15/39) compared with patients who did not meet these clinical criteria but who had MSI+ tumours (groups 3 and 4; 8/27 patients). Affected relatives of patients with hMLH1 mutations showed a significantly higher frequency of colorectal cancer but a lower frequency of endometrium cancer than those with hMSH2 mutations. CONCLUSIONS: MSI in tumour tissue is a useful criterion for selecting patients who should be tested for germline mutations in the mismatch repair genes hMSH2 and hMLH1 irrespective of their family history. Among carriers of hMSH2 mutations the tumour spectrum was broader than among carriers of hMLH1 mutations.     

Identification and Classification of Hereditary Nonpolyposis Colorectal Cancer (Lynch Syndrome): Adapting Old Concepts to Recent Advancements. Report from the Italian Association for the Study of Hereditary Colorectal Tumors Consensus Group

Knowledge about hereditary nonpolyposis colorectal cancer (HNPCC)/Lynch syndrome clearly evolved during the last 10 to 15 years much more rapidly than in the past century. Consequently, long-established concepts and attitudes that held for many years should now be changed or updated. With regard to classification, we suggest maintaining the eponym "Lynch syndrome" for families that have a well-documented deficiency of the DNA mismatch repair system, whereas "clinical hereditary nonpolyposis colorectal cancer" should be reserved for those families that meet the Amsterdam criteria but without evidence of mismatch repair impairment. Any family (or individual) meeting one or more of the Bethesda criteria can be considered as suspected HNPCC. For the identification of hereditary colorectal cancer molecular screening or the pedigree analysis show advantages and disadvantages; the ideal would be to combine the two approaches. Diffusion of the microsatellite instability test and of immunohistochemistry in the pathology laboratories might render in the immediate future molecular screening more realistic. Strict endoscopic surveillance of family members at risk (with first colonoscopy at age 20-25 years and then every 2-3 years) is needed only in families with documented alterations of the DNA mismatch repair. To a certain extent, our conclusions were similar to the recently proposed "European guidelines for the clinical management of HNPCC," although we prefer the term "clinical hereditary nonpolyposis colorectal cancer," instead of familial colorectal cancer, for families meeting the Amsterdam criteria but not having evidence of mismatch repair impairment.     

Basic concepts for genetic testing in common hereditary colorectal cancer syndromes

Approximately 5% of colorectal cancers are associated with one of the autosomal dominant hereditary cancer syndromes. The two most common familial colon cancer syndromes are familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). The causative mutation can be identified in many families with these syndromes by genetic testing of an affected individual. If an affected individual tests positive for a disease-causing mutation, genetic testing of unaffected, at-risk family members can be performed to determine whether they have inherited the cancer-susceptibility mutation, and a personalized cancer surveillance strategy can be devised. Genetic testing significantly enhances cancer risk assessment in these families. However, the complicated nature of result interpretation and the emotional impact of the result necessitate that testing be carried out in conjunction with patient education and informed consent by a physician who has a keen appreciation for the inherent challenges. This article describes the genetic testing strategy in HNPCC and FAP.     

Families at risk of colon cancer II. Hereditary nonpolyposis colorectal carcinoma

Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant inherited disease characterised by almost inevitable development of colorectal carcinoma and/or endometrium and other defined malignancies in affected individuals. HNPCC is caused by a germline mutation in a mismatch repair genes (MMR). The purpose of this review is to summarize current knowledge regarding HNPCC with the focus on recent data on genetic testing, surveillance guidelines and therapy. Available medical databases were searched from 1998 to May 2003 using the keywords "hereditary nonpolyposis colorectal cancer", followed by further search for particular issues. Additional articles were identified through the reference sections of retrieved articles and from personal archive of authors. Approximately 200 papers on HNPCC are published yearly. The major progress in recent research of HNPCC has been made in the area of genetic testing and clinical surveillance. Current guidelines recommend identification of microsatelite instability in a tumour of affected family member followed by germline testing in this person. Once mutation in particular MMR gene is found, screening of all at risk members is recommended. Alternative approach suggests direct germline testing in unaffected family member provided that the testing in affected member is not possible. Annual colonoscopy examinations starting at 20-25 years and gyneacological examination starting at 30-35 years are recommended in all family members at risk. Recent advances in genetic tests and surveillance strategies result in decreased mortality of HNPCC patient.     

Suspected hereditary nonpolyposis colorectal cancer

PURPOSE: The aim of this study was to determine the frequency of mutations in the mismatch repair genes in families suspected of having hereditary nonpolyposis colorectal cancer. METHODS: We devised two criteria for families suspected of having hereditary nonpolyposis colorectal cancer (Criteria I and II). Criteria I consist of at least two first-degree relatives affected with colorectal cancer with at least one of the following: development of multiple colorectal tumors including adenomatous polyp, at least one colorectal cancer case diagnosed before the age of 50, and occurrence of a hereditary nonpolyposis colorectal cancer extracolonic cancer (endometrium, urinary tract, small intestine, stomach, hepatobiliary system, or ovary) in family members. Criteria II consist of one colorectal cancer patient with at least one of the following: early age of onset (<40 years); endometrial, urinary tract, or small intestine cancer in the index patient or a sibling (one aged <50 years); and two siblings with other integral hereditary nonpolyposis colorectal cancer extracolonic cancers (one aged <50 years). A questionnaire was mailed to members of the International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer to determine the mutation detection rate in mismatch repair genes from the families fulfilling these criteria. For comparison the mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria in each institution was also obtained. RESULTS: Data were obtained from eight different institutions (in 7 different countries). In a total of 123 patients from 123 families (67 families fulfilling Criteria I and 56 families fulfilling Criteria II), genetic testing for germline mismatch repair gene variants was performed. Germline mutations of the hMLH1 or hMSH2 genes were identified in 24 families (20 percent). Of these, the mutation detection rate for families fulfilling Criteria I was 28 percent (19/67). The mutation detection rate for families fulfilling Criteria II was 9 percent (5/56). In these eight institutions, the overall mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria was 50 percent (77/154). CONCLUSION: The Criteria I for suspected hereditary nonpolyposis colorectal cancer have the advantages that they can be applied to nuclear families and they can include extracolonic cancers. The results of this study suggest that families fulfilling Criteria I should be offered genetic testing. The relatively low mutation detection rate in those families fulfilling Criteria II suggests that, using current techniques, genetic testing in these families is not practical.     

Colonic cancer in a 34-yr-old woman: should it prompt microsatellite instability studies and mismatch repair gene testing?

It remains debatable whether young patients with colorectal tumors should undergo genetic testing with the aim of identifying new hereditary nonpolyposis colorectal cancer families. We describe a case of a young woman with colon cancer with no clinical criteria of hereditary nonpolyposis colorectal cancer, whose genetic analysis showed that the tumor displayed microsatellite instability, and in whom a truncated protein in hMSH2 gene was found, which was also present in two at-risk relatives.     

Estimated prevalence of hereditary cancers and the need for surveillance in a Norwegian county, Telemark

OBJECTIVE: The aim of the study was to estimate the prevalence of hereditary cancers and the need for surveillance in Telemark county, Norway. MATERIAL AND METHODS: All persons attending the Norwegian Colorectal Cancer Prevention (NORCCAP) trial in Telemark were interviewed about cases of cancer in the family. Diagnoses were verified, pedigrees constructed and families classified according to preset criteria aiming at identifying hereditary cancer. Mutation analyses were performed in kindreds at risk for breast cancers when possible. Immunohistochemistry of tumors in assumed inherited colorectal cancer families was undertaken. RESULTS: The screening examination was attended by 7,224 persons among whom 2,866 had cancer in the family. Of these, 2,479 had no suspicion of any known inherited cancer syndrome. Family information questionnaires were mailed to 387 persons and returned by 191. Sixty-four of these 191 met the clinical criteria for familial cancer by family history after verification of diagnoses. Observed prevalences for being at risk for hereditary breast and breast-ovarian cancer (HBOC) or hereditary non-polyposis colorectal cancer (HNPCC) were 2.8 per thousand and 0.77 per thousand, respectively. CONCLUSIONS: The number of colonoscopies and mammograms obtained per year serving those who needed them was limited and reduced by clinical genetic work-up from 2,866 with a family history of cancer to 64 proven cases. Continued surveillance of an unnecessarily high number leads to unjustified cancer worry, is costly and uses up health-care facilities. Genetic work-up is a one-time job that reduces input numbers to surveillance programs, provides a starting-point for mutation testing and is economically cost beneficial if inherited cancers are prevented or cured by the health-care programs offered.     

Genetic testing for maturity onset diabetes of the young: uptake, attitudes and comparison with hereditary non-polyposis colorectal cancer

Aims/hypothesis Mutations in hepatic nuclear factor 1 cause a monogenic form of diabetes, maturity onset diabetes of the young type 3 (MODY3). Our aim was (1) to assess the uptake of genetic testing for MODY3 and to determine factors affecting it, and (2) to compare attitudes to predictive genetic testing between families with MODY3 and a previously studied group at risk of hereditary non-polyposis colorectal cancer (HNPCC).Methods Adult members of two extended MODY3 pedigrees, either with diabetes or a 50% risk of having inherited the mutation (n=144, age 18–60 years), were invited to an educational counselling session followed by a possibility to obtain the gene test result. Data were collected through questionnaires before counselling and 1 month after the test disclosure.Results Eighty-nine out of 144 (62%) participated in counselling, and all but one wanted the test result disclosed. No significant sociodemographic differences were observed between the participants and non-participants. The counselling uptake was similar among diabetic and non-diabetic subjects. Uncertainty about the future and the risk for the children were the most common reasons to take the gene test. At follow-up, most subjects in both MODY3 (100%) and HNPCC (99%) families were satisfied with their decision to take the test and trusted the result. The majority of both diabetic and non-diabetic subjects considered that the MODY3 gene test should be offered either in childhood (50 and 37%) or as a teenager (30 and 37%).Conclusions Genetic testing for MODY3 was well accepted among both diabetic and non-diabetic participants. The subjects found the gene test reliable and they were satisfied with their decision regarding the predictive test.     

Clinicopathologic characteristics of Chinese hereditary non‐polyposis colorectal cancer

OBJECTIVE: The aim of the present study was to examine the clinicopathologic characteristics of Chinese patients with hereditary non‐polyposis colorectal cancer (HNPCC) and those with suspected (atypical) HNPCC. METHODS: Personal and family cancer histories were obtained by reviewing the charts and interviewing the proband and participating relatives. Families were identified and classified into three groups by either the Amsterdam or Japanese criteria for HNPCC. Clinical characteristics including onset, localization, stage of colorectal cancer (CRC), tumor multiplicity, survival and mucinous histology were evaluated. RESULTS: Ninety‐eight subjects comprising 92 CRC patients and six extracolonic cancer patients from 13 typical and 19 non‐typical HNPCC kindreds were enrolled. There were 53 patients with CRC, one with both CRC and extracolonic cancer and five with extracolonic cancer in the typical HNPCC group, and in the atypical group there were 38 patients with CRC and one with extracolonic cancer. The average onset age of typical HNPCC and atypical HNPCC was 48 and 50 years, respectively, without statistical difference. There were no statistical differences in sex, pathological type, stage, site distribution of the tumor or survival between typical HNPCC and atypical HNPCC groups. There were 11.1% (6/54) metachronous CRC in the typical HNPCC group, and 7.9% (3/38) metachronous and 2.6% (1/38) synchronous CRC in the atypical HNPCC group. CONCLUSION: The Amsterdam criteria are important, but inappropriate for the establishing the clinical diagnosis of HNPCC in Chinese patients, with some atypical families that did not fulfil all the Amsterdam criteria probably possessing similar clinicopathogical features and genetic alterations. It seems that HNPCC should be considered in some suspected cases.     

Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

AIM: To detect microsatellite instability (MSI) in patients with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer and to provide criteria for screening the kindreds with hereditary nonpolyposis colorectal cancer at molecular level. METHODS: MSI was detected in the specimens from 20 cases with HNPCC, 20 cases with ordinary hereditary colorectal cancer and 20 cases with sporadic colorectal cancer by means of polymerase chain reaction-single strand conformation polymorphism. RESULTS: The positive rate of MSI was 85% (17/20) in HNPCC group, 40% (8/20) in ordinary hereditary colorectal cancer group and 10% (2/20) in the sporadic colorectal cancer group respectively. The differences were significant. The mean ages of the three groups were 43.6, 52.2, and 61.8 years respectively, which increased gradually. The incidence of right hemicolon cancer was 64.7%, 37.5%, and 0% respectively, which decreased gradually and had significant difference. The expression ratio of BAT26 and BAT25 was 94.1% respectively, which was highest in the 5 gene sites studied. The incidence of poorly differentiated adenocarcinoma was 70.6% in HNPCC group among high frequency microsatellite instability (MSI-H), which was higher than the other two groups, which had 50% and 50% respectively. CONCLUSION: The incidence of MSI-H is higher in HNPCC group. The detection of MSI is simple and economical and has high correlation with the clinicopathologic feature of HNPCC and can be used as a screening method to detect the germ line mutation of the mismatch repair gene.