Phenotypic variation in colorectal adenoma/cancer expression in two families. Hereditary flat adenoma syndrome

Candidate Gene Discovery in Hereditary Colorectal Cancer and Polyposis Syndromes-Considerations for Future Studies

To discover novel high-penetrant risk loci for hereditary colorectal cancer (hCRC) and polyposis syndromes many whole-exome and whole-genome sequencing (WES/WGS) studies have been performed. Remarkably, these studies resulted in only a few novel high-penetrant risk genes. Given this observation, the possibility and strategy to identify high-penetrant risk genes for hCRC and polyposis needs reconsideration. Therefore, we reviewed the study design of WES/WGS-based hCRC and polyposis gene discovery studies (n = 37) and provide recommendations to optimize discovery and validation strategies. The group of genetically unresolved patients is phenotypically heterogeneous, and likely composed of distinct molecular subtypes. This knowledge advocates for the screening of a homogeneous, stringently preselected discovery cohort and obtaining multi-level evidence for variant pathogenicity. This evidence can be collected by characterizing the molecular landscape of tumors from individuals with the same affected gene or by functional validation in cell-based models. Together, the combined approach of a phenotype-driven, tumor-based candidate gene search might elucidate the potential contribution of novel genetic predispositions in genetically unresolved hCRC and polyposis.

Large intron 14 rearrangement in APC results in splice defect and attenuated FAP

Familial adenomatous polyposis [FAP (OMIM 175100)] is an autosomal dominant colorectal cancer predisposition syndrome characterized by hundreds to thousands of colonic polyps and, if untreated by a combination of screening and/or surgical intervention, an approximately 99% lifetime risk of colorectal cancer. A subset of FAP patients develop an attenuated form of the condition characterized by lower numbers of colonic polyps (highly variable, but generally less than 100) and a lower lifetime risk of colorectal cancer, on the order of 70%. We report the diagnosis of three attenuated FAP families due to a 1.4-kb deletion within intron 14 of APC, originally reported clinically as a variant of unknown significance (VUS). Sequence analysis suggests that this arose through an Alu-mediated recombination event with a locus on chromosome 6q22.1. This mutation is inherited by family members who presented with an attenuated FAP phenotype, with variable age of onset and severity. Sequence analysis of mRNA revealed an increase in the level of aberrant splicing of exon 14, resulting in the generation of an exon 13-exon 15 splice-form that is predicted to lead to a frameshift and protein truncation at codon 673. The relatively mild phenotypic presentation and the intra-familial variation are consistent with the leaky nature of exon 14 splicing in normal APC. The inferred founder of these three families may account for as yet undetected affected branches of this kindred. This and similar types of intronic mutations may account for a significant proportion of FAP cases where APC clinical analysis fails because of the current limitations of testing options.

[Hereditary colorectal cancer]

One of the main challenges in the clinical management of familial colorectal cancer (CRC) remains the overlap of syndromes with different underlying genetic causes and the differentiated risk management of colorectal and associated malignancies. The Lynch syndrome (hereditary non-polyposis colorectal cancer, HNPCC) is characterized by the development of colorectal, endometrial, gastric and other cancers and is caused by a mutation in one of the mismatch repair (MMR) genes. Microsatellite instability (MSI) and/or immunohistochemistry (IHC) are important prognostic factors and may predict the response to chemotherapy. Familial adenomatous polyposis (FAP) may be seen as a counterpart to Lynch syndrome, responsible for <1% of all CRC cases. Recently the MUTYH gene has been identified as a further polyposis gene. The associated disorder has been termed MYH-associated polyposis (MAP) and displays an autosomal recessive pattern of inheritance. For clinical management, distinguishing between Lynch syndrome, attenuated FAP and MAP is important for risk assessment, surveillance recommendations and indication for prophylactic surgery.

Variable Phenotypic Expression of Identical MYH Germline Mutations in Siblings with Attenuated Familial Adenomatous Polyposis

Germline mutations in the Mutant-Y-homologue (MYH) gene have been linked to an attenuated form of familial adenomatous polyposis in patients who express a wild-type adenomatous polyposis coli gene. However, the diverse clinical manifestations of MYH mutations have not been fully elucidated. We report a case of siblings with identical germline mutations in the MYH gene, one of whom developed a locally advanced colon adenocarcinoma with few other adenomatous lesions, whereas the other had numerous benign colonic polyps. The variable genotype–phenotype manifestations of MYH mutations and the attenuated familial adenomatous polyposis syndrome are discussed.

Colonic and duodenal flat adenomas in children with classical familial adenomatous polyposis

Flat adenomas of the colon and duodenum have been described as associating with familial adenomatous polyposis (FAP), its attenuated variant, and the so-called hereditary nonpolyposis colorectal cancer. There seem to be no report on the occurrence of flat adenomas in pediatric patients with family history of FAP. We are reporting 4 children from 2 cancer-prone families in whom colonic and duodenal moderately dysplastic flat adenomas were found. Gastrointestinal endoscopy and biopsies were performed in 3 female siblings (7, 9, and 11 years old) and 1 male (9 years old) when referred for screening owing to familial history of bowel cancer (family 1) or evidence of bilateral congenital hypertrophy of the retinal pigment epithelium (CHRPE), which is known to be associated with FAP (family 2). Endoscopic visualization of the mucosa was improved by use of 0.2% indigo carmine solution spray. Biopsies were routinely processed for H&E and immunohistochemistry staining. Present patients were asymptomatic, with the exception of 2 weeks rectal bleeding in 1 of them. The colonic videoendoscopy showed in 2/3 siblings hundreds of flat or slightly raised plaques less than 1 cm in diameter as well as some classic polyps throughout the colon. The other sibling showed 40 flat-topped lesions with minimal elevation and central umbilication in the cecum. Upper endoscopy demonstrated a few flat lesions in the nonperiampullary area of the duodenum in 2/4 patients. The colonic videoendoscopy performed on the 9-year-old boy revealed multiple small sessile polyps. Microscopic study demonstrated tubular adenomas with a few neoplastic crypts, slight disarray of the overall architecture, and moderate (low-grade) dysplasia of the epithelium. These features were more obvious at the center and superficial areas of the adenomas. The 4 children had multiple flat adenomas of the colon and duodenum (2/4) matching with those described in adult patients. Flat adenomas in the context of FAP probably represent early stages of the adenoma development. Careful endoscopic-histologic correlation may result in increasing recognition of these lesions at the pediatric age.

Intraductal papillary mucinous neoplasm of the pancreas in a patient with attenuated familial adenomatous polyposis

A 67 year old man with a clinical diagnosis of attenuated familial adenomatous polyposis (AFAP) and a past history of synchronous colon cancers in the transverse colon was also found to have an intraductal papillary mucinous neoplasm (IPMN) of the pancreas. In addition, several foci of heterotopic gastric oxyntic mucosa were noted in the duodenum, interspersed with flat and polypoid adenomas. The duodenal adenomas showed low grade dysplasia, loss of adenomatous polyposis coli (APC) protein expression, but retention of beta catenin staining, localised to the nucleus and cytoplasm. The IPMN in the pancreas showed an identical immunohistochemical profile to the duodenal adenomas. The heterotopic gastric foci in the duodenum were negative for the APC protein, and beta catenin staining was membranous in location. Although the patient did not show germline truncating APC mutations or mutations in the MYH gene, the past history, clinical features, and immunohistochemical profile of the various lesions suggest strongly that the IPMN is part of the spectrum of lesions encountered in AFAP. Whether the heterotopic oxyntic gastric mucosa in the duodenum is also related is unclear, but it may represent a forme fruste of fundic gland polyps.

Preventive surgery for colon cancer in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer syndrome

BACKGROUND

A better understanding of the molecular basis of hereditary colorectal cancer syndromes such as hereditary nonpolyposis colorectal cancer syndrome (HNPCC) and familial adenomatous polyposis (FAP) has profound consequences for both the diagnosis and (prophylactic) treatment of (pre)malignant neoplastic lesions.

DISCUSSION

Sequence analysis of the underlying genes for these conditions and the detection of disease-causing genetic alterations in an index patient enable predictive testing for individuals at risk within an affected family. However, the clinical implications of predictive molecular testing depend on the overall penetrance and variability in the expression of pathogenic mutations. The extent of these parameters differs considerably among the various known hereditary colorectal cancer syndromes. Hence the integration of genetic information into the daily surgical practice remains challenging.

CONCLUSIONS

This review provides an update on the indications for family assessment, purpose and limitations of the genetic testing and resulting recommendations for prophylactic surgery in FAP and HNPCC.

Early detection of colorectal cancer using high-magnification chromoscopic colonoscopy

BACKGROUND

Endoscopic techniques aimed at early detection of colorectal cancer (CRC) and its precursors, permitting targeted in vivo luminal treatments, have been developed by the Japanese since the early 1990s. The introduction of this new technology to the UK (i.e. magnification endoscopes) may permit earlier and more accurate diagnosis. According to Japanese data, magnification chromoscopy can be used to predict histology and invasive depth of cancer, and help in the detection of flat and depressed colonic lesions. Flat and depressed lesions are not purely Japanese phenomena: they exist with a similar incidence in the UK.

METHODS

A Medline search was performed for the years 1955-2001 using the following medical subject headings and search methodology: colorectal cancer and colonoscopy or aberrant crypt foci or molecular kinetics or flat/depressed lesions or chromoscopy.

RESULTS AND CONCLUSION

Early CRC, in the form of flat or depressed lesions, can be difficult to detect using conventional colonoscopic techniques and penetrate the colonic mucosa deeply. The implications of detecting these lesions in relation to current approaches to the prevention of CRC are profound.

Giant fundic polyp complicating attenuated familial adenomatous polyposis

This case details the development of a rapidly growing polypoid mass in the proximal stomach in a patient with known attenuated familial adenomatous polyposis. Surgical resection was required and histology showed hyperplasia with extensive areas of dysplastic adenomatous change. This case illustrates that patients with the attenuated form of familial adenomatous polyposis are at risk for multiple neoplasia distinct from those patients with the classic form of familial adenomatous polyposis.

Genetic pathways in colorectal and other cancers

Cells from cancers show aberrant behaviour such as unrestrained growth, invasion into adjacent tissue and metastasis. All these features of cancer cell behaviour can be explained in terms of genetic changes and the functional impact of these changes. In this review, colorectal cancer (CRC) is examined as a classical example of multistep carcinogenesis. First there is an overview which shows that cancers develop by a process of somatic evolution. This gives rise to preferred genetic pathways of tumorigenesis. The factors which may influence the development and ultimate choice of genetic pathways are then examined. Next, CRC is studied as a specific disease and the putative genetic pathways are described. The mutations that comprise these pathways and the possible functional sequelae of these are explored. The review concludes with a look at those avenues which may further elucidate the natural history of CRC and lead to improved therapy.

Genetic pathways in colorectal and other cancers

Cells from cancers show aberrant behaviour such as unrestrained growth, invasion into adjacent tissue and metastasis. All these features of cancer cell behaviour can be explained in terms of genetic changes and the functional impact of these changes. In this review, colorectal cancer (CRC) is examined as a classical example of multistep carcinogenesis. First there is an overview which shows that cancers develop by a process of somatic evolution. This gives rise to preferred genetic pathways of tumorigenesis. The factors which may influence the development and ultimate choice of genetic pathways are then examined. Next, CRC is studied as a specific disease and the putative genetic pathways are described. The mutations that comprise these pathways and the possible functional sequelae of these are explored. The review concludes with a look at those avenues which may further elucidate the natural history of CRC and lead to improved therapy.

Hepatoblastoma and APC gene mutation in familial adenomatous polyposis

BACKGROUND

Hepatoblastoma is a rare, rapidly progressive, usually fatal childhood malignancy, which if confined to the liver can be cured by radical surgical resection. An association between hepatoblastoma and familial adenomatous polyposis (FAP), which is due to germline mutation of the APC (adenomatous polyposis coli) gene, has been confirmed, but correlation with site of APC mutation has not been studied.

AIM

To analyse the APC mutational spectrum in FAP families with hepatoblastoma as a possible basis to select kindreds for surveillance.

PATIENTS

Eight patients with hepatoblastoma in seven FAP kindreds were compared with 97 families with identified APC gene mutation in a large Registry.

METHODS

APC gene mutation was evaluated by RNase protection assay or in vitro synthesis protein assay. The chi 2 test and correlation were used for data analysis.

RESULTS

APC gene mutation was identified in all seven FAP kindreds in which an at risk member developed hepatoblastoma. A male predominance was noted (six of eight), similar to literature cases (18 of 25, p < 0.01. Mutations were restricted to codons 141 to 1230, but no significant difference in site of mutation between pedigrees with and without hepatoblastoma was identified.

CONCLUSIONS

Hepatoblastoma occurs primarily in boys in FAP kindreds and is associated with germline APC mutation in the 5' end of the gene. However, the site of APC mutation cannot be used to predict occurrence of this extracolonic cancer in FAP pedigrees.

Flat adenoma as a precursor of colorectal carcinoma in hereditary nonpolyposis colorectal carcinoma

BACKGROUND

Because flat adenoma shows a higher malignancy rate compared with other types of polyps, it is considered to play an important role in the carcinogenesis of colorectal carcinoma. In the present study, we examined flat adenomas in hereditary nonpolyposis colorectal carcinoma (HNPCC) patients.

METHODS

Nine HNPCC patients who presented with flat adenomas were examined. All patients underwent either surgery or endoscopic polypectomy for colorectal carcinoma and/or adenoma. In all patients, annual colonoscopy had been performed once a year throughout the follow-up period after the initial treatment. When colorectal polyps were detected during follow-up colonoscopy, all lesions were endoscopically excised. Clinicopathologic features and microsatellite instability of both malignant lesions and adenomas were examined.

RESULTS

Thirteen malignant lesions were detected: seven advanced carcinomas and six early carcinomas. Among 4 early carcinomas with submucosal invasion, 3 lesions (75%) were categorized as superficial type, with a configuration similar to flat adenoma. The frequency of flat adenoma was strikingly high in HNPCC patients in the present study. Among 73 polyps detected, 37 (50.7%) were flat adenomas. Both malignant lesions and flat adenomas had proximal predominance, 61.5% and 59.5%, respectively. Eleven of 15 lesions (73.3%) showed replication error.

CONCLUSIONS

These results suggest the importance of flat adenoma as a precursor of colorectal carcinoma in some groups of HNPCC patients. Further study is essential to elucidate the natural history of flat adenomas in HNPCC patients.

Attenuated familial adenomatous polyposis (AFAP). A phenotypically and genotypically distinctive variant of FAP

BACKGROUND

The usual manifestation of familial adenomatous polyposis (FAP) is hundreds or thousands of colonic adenomas. The authors previously described a colon cancer-prone syndrome characterized by fewer adenomas (1-100), most located in the proximal colon, and upper gastrointestinal lesions, particularly fundic gland polyps and duodenal adenomas. The colonic adenomas are often flat rather than polypoid, a feature emphasized in earlier reports with the term "hereditary flat adenoma syndrome." The syndrome has an autosomal dominant pattern of inheritance and is linked to the adenomatous polyposis coli (APC) locus at 5q.

METHODS

This is a descriptive study based on one family that was followed for more than a decade. Total cell RNA was isolated from cultured lymphoblasts, and an in vitro protein synthesis assay was used to detect APC mutations. Sixteen individuals whose APC mutation status was known had sequential endoscopic evaluations. Five patients were given one or more courses of sulindac.

RESULTS

There was perfect concordance between clinical affected status and an APC mutation. All affected members generated a 16-kDa polypeptide from the mutant allele, consistent with a 2-base pair deletion at the extreme 5' end of the APC gene. Sixteen mutation-positive individuals underwent upper gastrointestinal endoscopy and colonoscopy; 13 had colonic adenomas, with the number visualized at any one examination ranging from 1 to greater than 50. Upper gastrointestinal examination revealed fundic gland polyps in 15, gastric or duodenal adenomas in 4, and periampullary carcinoma in 1.

CONCLUSION

AFAP is a phenotypically distinctive syndrome, differing from classic FAP by having fewer colonic adenomas that tend to be proximally distributed and flat rather than polypoid. The position of the APC germline mutation appears to allow for the molecular differentiation between FAP and the attenuated variant in that the extreme 5' APC mutations are associated with the latter.

Upper gastrointestinal manifestations in families with hereditary flat adenoma syndrome

BACKGROUND

The hereditary flat adenoma syndrome (HFAS) is characterized by an autosomal dominantly inherited predisposition to multiple colonic adenomas (usually less than 100) with proximal predominance and flat as opposed to polypoid growth. Patients with the syndrome experience colorectal cancers in excess, and the lesions are distributed randomly in the colon. The polyps occur at a later age (median, 55 years) compared with age at onset of polyps in patients with familial adenomatous polyposis (FAP) and patients with the Lynch syndromes. FAP and HFAS are linked to the same locus on chromosome 5q21-q22.

METHODS

Upper endoscopic examination was performed on 22 relatives from four families with HFAS.

RESULTS

Fifteen patients from three of these families had multiple fundic gland polyps; four had duodenal or gastric adenomas. Periampullary carcinoma was present in two members from separate families.

CONCLUSIONS

The authors conclude that the upper gastrointestinal tract pathologic characteristics of HFAS are similar to those described in FAP. Thus, those at risk for HFAS require upper endoscopic screening in addition to meticulous attention to the colon.

Genetics, natural history, tumor spectrum, and pathology of hereditary nonpolyposis colorectal cancer: an updated review

Hereditary nonpolyposis colorectal cancer (HNPCC) dates to Warthin's description of family G, which he began studying in 1895. Warthin's observations were not fully appreciated until 1966 when two families with an autosomal dominant inheritance pattern of nonpolyposis colorectal cancer (CRC) and endometrial cancer were described. This condition was first termed the "cancer family syndrome" and was later renamed HNPCC. Some have proposed that HNPCC consists of at least two syndromes: Lynch syndrome I, with hereditary predisposition for CRC having early (approximately 44 years) age of onset, a proclivity (70%) for the proximal colon, and an excess of synchronous and metachronous colonic cancers and Lynch syndrome II, featuring a similar colonic phenotype accompanied by a high risk for carcinoma of the endometrium. Transitional cell carcinoma of the ureter and renal pelvis and carcinomas of the stomach, small bowel, ovary, and pancreas also afflict some families. Current estimates indicate that HNPCC may account for as much as 6% of the total CRC burden. There are no known premonitory phenotypic signs or biomarkers of cancer susceptibility in the Lynch syndromes. This report will summarize current knowledge, with emphasis on the manner in which this knowledge can be employed effectively for diagnosis and management of HNPCC.

Extracolonic cancer in hereditary nonpolyposis colorectal cancer

BACKGROUND

It has been hypothesized that in some but not all families with hereditary nonpolyposis colorectal cancer (HNPCC) there is a high risk of certain cancers other than colon cancer.

METHODS

The authors compared the observed frequency of cancer at specific sites in more than 1300 high-risk members of 23 kindreds with HNPCC with expectations based on general population incidence and evaluated the hypothesis that there was heterogeneity in cancer frequency among families.

RESULTS

The authors observed significantly increased numbers of cancers of the stomach, small intestine, upper urologic tract (renal pelvis and ureter), and ovary. No excess was seen in other cancer types that have been associated previously with HNPCC, including cancer of the breast, pancreas, and urinary bladder. Significant heterogeneity among families was observed in the frequencies of endometrial, ovarian, and upper urologic system cancer.

CONCLUSION

In addition to early onset cancers of the colorectum, HNPCC family members are at increased risk for cancers of other gastrointestinal tract organs, and, especially in some families, cancers of the upper urologic and female genital tract.

Epidemiologic characteristics of the flat adenoma of Muto. A prospective study

The flat adenoma is an endoscopically visible lesion that histologically consists of adenomatous change near the luminal surface of colonic tubules. We have described three families with hereditary colon cancer with later age of onset than familial adenomatous polyposis (FAP) and with multiple proximal colonic flat adenomas. These families have been linked to the FAP locus on chromosome 5. Our aim was to determine whether the flat adenoma is pathognomonic of this hereditary flat adenoma syndrome (HFAS) or merely an atypical or early tubular adenoma with occurrence in patients other than those from colon cancer-prone families.

METHODS

We prospectively examined a population referred for colonoscopy within a one-year period. During colonoscopy, flat adenomas were specifically sought and all lesions were removed endoscopically and evaluated histologically. Members of known hereditary colon cancer families were excluded.

RESULTS

One hundred forty-eight patients underwent colonoscopy (64 men and 84 women). Median age was 61 years. Fifty-seven patients had 157 polyps. One hundred thirty-six polyps were reviewed histologically. Thirty-five (23.6 percent) of the referred patients had adenomas, of whom twelve patients had only flat adenomas while six had both flat and other adenomas (18 = 12 percent of 148). The associations between flat adenoma occurrence and various predictors (sex, race, prior colonic neoplasms, family history of cancer, synchronous adenomas) were similar to those seen with other adenomas. Flat adenomas were found in nearly equal proportions of patients under or over age 61 years (11 percent and 13 percent, respectively). Other adenomas were significantly more common in the older group (6 percent vs. 25 percent; P less than 0.002 by Fisher's exact test).

CONCLUSION

In a referral practice, the flat adenoma has the same prevalence and associated risk factors as other adenomas, except for younger age of onset. Our data suggest that the flat adenoma represents an early stage of adenoma development that is manifested in a subset of patients from the general population and that, as an isolated event, does not provide a marker for a hereditary colon cancer-prone syndrome.

Screening for large bowel neoplasms in individuals with a family history of colorectal cancer

Logistical problems associated with population screening for colorectal cancer are identified and the possibility of targeting screening to those with a familial predisposition to the disease is discussed. Evidence for a substantial genetic effect on the overall incidence of colorectal cancer is reviewed. The screening detection rate of colorectal neoplasms in relatives of patients with colorectal cancer has been shown to be higher than that expected in a non-selected population; the evidence that polypectomy will reduce future colorectal cancer risk in such individuals is explored. Recent advances in the molecular genetics of colorectal cancer susceptibility are reviewed; it is possible that a genetic test might be developed in the future which could identify at least a proportion of those at risk. Excluding financial considerations, the risk-benefit ratio of colonoscopy in a screened population is intimately related to the remaining risk of colorectal cancer in those who undergo the examination. At present, patients undergoing colonoscopy to investigate a positive faecal occult blood (FOB) test as part of a population-based screening programme include individuals with a familial predisposition as well as those without. About 20 per cent of all cases of colorectal cancer are associated with an obvious genetic predisposition, and the risk of cancer in their relatives is high. Because false positives occur with Haemoccult, the residual risk to the population who are FOB positive but do not have a familial trait may be sufficiently low that the dangers of colonoscopy could outweigh the potential benefits. Scotland has a high incidence of colorectal cancer, and analysis of recent Scottish incidence data shows an actuarial lifetime risk of developing this disease of one in 23 for men and one in 33 for women. As a family history of the disease increases that risk by two to four times and the neoplasms arise throughout the colon in such a group, there may be a case for offering colonoscopy to all first-degree relatives of those under 50 years of age at diagnosis, if not of all index cases of colorectal cancer.

Hereditary flat adenoma syndrome: a variant of familial adenomatous polyposis?

We describe the clinical and pathologic features in four extended kindreds that are consistent with the hereditary flat adenoma syndrome (HFAS). This colon cancer susceptibility disorder is believed to be inherited as an autosomal dominant. The principal phenotypic marker is multiple colonic adenomas (usually less than 100), with a tendency for proximal location. The majority of these adenomas are flat or slightly raised and plaquelike, as opposed to polypoid. Colon cancers have typically developed in middle age and show no unusual histologic features. There are a variety of extracolonic manifestations, including adenomas and carcinomas of the small bowel and fundic gland polyps. The HFAS is contrasted with hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis (FAP) and shown to be distinct from both in the numbers and distribution of colonic adenomas and the typical age of cancer diagnosis. The clinical implications of these findings are discussed. Given its linkage to the FAP locus on 5q and the phenotypic parallels between HFAS and FAP, we conclude that HFAS is a variant of FAP.

Hereditary nonpolyposis colorectal cancer (Lynch syndromes I & II). Genetics, pathology, natural history, and cancer control, Part I

Hereditary nonpolyposis colorectal cancer (HNPCC) is common, accounting for about 4-6% of the total colorectal cancer burden. It is heterogeneous and appears to be delineated into two clinical subsets, Lynch syndromes I and II. Lynch syndrome I is characterized by an autosomal dominantly inherited proclivity to early onset colonic cancer with proximal predominance and an excess of multiple primary colonic cancer. Lynch syndrome II has all of these features plus extracolonic cancer sites, the most common of which is endometrial carcinoma. The lack of premonitory physical signs or biomarkers of HNPCC makes diagnosis difficult. A careful family history, tempered by an understanding of the clinical and pathologic features of HNPCC, is the key to its assessment. This paper reviews HNPCC's natural history, its integral extracolonic cancer associations, its differential diagnosis, surveillance, and management strategies. Attention is focused upon the need for biomarker research in the interest of improving control of HNPCC.