APC gene mutations and extraintestinal phenotype of familial adenomatous polyposis.

BACKGROUND: Familial adenomatous polyposis (FAP) is caused by germline mutation of the adenomatous polyposis coli (APC) gene on chromosome 5q. AIMS: This study assessed genotype-phenotype correlations for extraintestinal lesions in FAP. METHODS: Mutations of the APC gene were compared with the occurrence of seven extraintestinal manifestations in 475 FAP patients from 51 families. The frequency of manifestations was adjusted for different ages of patients using person years of exposure. In pedigrees without identified APC gene mutation, analysis of linkage to chromosome 5q and/or assessment of neoplasms for replication errors characteristic of mutation in mismatch repair genes were performed. RESULTS: FAP patients from the 42 families (82%) with identified mutations of the APC gene had more frequent expression of extraintestinal manifestations than affected individuals without identified mutations (risk ratio 1.2-4.0; significant difference for cutaneous cysts). The presence of a cutaneous cyst or extraintestinal cancer significantly increased the likelihood of detection of a mutation in the APC gene (94% and 92% respectively; p < 0.05). In patients without identified APC gene mutation, linkage to the APC gene was found in one large family (lod = 5.1, theta 0.01), and replication error phenotype was absent in all 24 neoplasms from 16 members of these nine pedigrees. Expression of pigmented ocular fundus lesions was strongly associated with mutations in codons 541-1309, but no other extraintestinal manifestations were related to mutation position. Multiplicity of extraintestinal manifestations was high with mutation in codons 1465, 1546, and 2621. CONCLUSIONS: Patients with the colorectal phenotype of FAP but no extraintestinal manifestations may have non-truncating mutations of the APC gene or mutation in a gene other than APC or mismatch repair genes. The site of APC gene mutation is associated with pigmented ocular fundus lesions (codons 542-1309) and predisposition to multiplicity of extraintestinal manifestations (codons 1465, 1546, and 2621).     

Genetic and clinical characterisation of familial adenomatous polyposis: a population based study

BACKGROUND: Familial adenomatous polyposis (FAP) is a rare autosomal dominantly inherited disease predisposing to colon cancer and caused by germline mutations in the APC (adenomatous polyposis coli) gene. AIMS: We conducted a population based study to evaluate the prevalence and clinical implications of APC mutations among Finnish FAP kindreds. A possible founder effect in parallel with previous observations in hereditary non-polyposis colon cancer (HNPCC) was addressed. PATIENTS: Affected individuals from 65 kindreds were included. METHODS: The APC gene was screened for mutations using the protein truncation test and heteroduplex analysis. Haplotype analysis was performed with four flanking microsatellite markers. Families that failed to show any mutations were scrutinised with Southern blot hybridisation and allelic expression analysis. RESULTS: Thirty eight different germline mutations in APC were identified in 47 kindreds (72%). The majority of these mutations were novel and unique to each family. Although sharing the classical polyposis phenotype, families without detectable APC mutations differed from mutation positive families in the following respects: firstly, mean age at polyposis diagnosis was higher (38.6 years (48 individuals) v 30.0 years (140 individuals); p=0.001); and secondly, the proportion of kindreds lacking extracolonic disease was higher (6/18 v. 5/47; p=0.04). CONCLUSIONS: Our results may pave the way for predictive testing in mutation positive families and should stimulate further molecular studies in mutation negative families. No founder effect was observed, which is in contrast with HNPCC in the same population.     

APC gene mutations in Chinese familial adenomatous polyposis patients

AIM:To study the characteristics of APC(adenomatous polyposis coli)gene germline mutation in Chinese patients with familial adenomatous polyposis(FAP).METHODS:APC gene from 14 FAP families was amplified by polymerase chain reaction(PCR)and underwent direct sequencing to determine the micromutation type.For the samples without micromutation,the large fragment deletion of APC gene was examined by multiplex ligation-dependent probe amplification(MLPA).RESULTS:There were gene micromutations in 9 families with a...     

Serrated adenoma in familial adenomatous polyposis: relation to germline APC gene mutation

BACKGROUND: Serrated adenoma is a precursor of colorectal cancer. AIM: To clarify possible genotype-phenotype correlations of serrated adenomas in familial adenomatous polyposis (FAP). Patients: Eleven patients from eight families with FAP. METHODS: We performed total colonoscopy with multiple biopsies in patients. Neoplasia with a serrated glandular structure was regarded as a serrated adenoma. In each patient, germline mutations of the APC gene were determined. Colonic phenotype was compared with germline mutations of the APC gene. RESULTS: Serrated adenomas were found in three patients. These patients had macroscopic polyps <100 in number. Pedigrees with serrated adenomas had the truncating germline APC mutation at codon 161, 332, or 1556 while in the other pedigrees mutations were found between codons 554 and 1324. CONCLUSIONS: In FAP, serrated adenoma may be a phenotype characteristic of the attenuated form.     

Singapore familial adenomatous polyposis (FAP) patients with classical adenomatous polyposis but undetectable APC mutations have accelerated cancer progression

OBJECTIVES: Germline mutation in adenomatous polyposis coli (APC) is detected in up to 80% of familial adenomatous polyposis (FAP) patients worldwide. In this study, we evaluated clinical features and APC mutations of Singapore FAP patients and contrasted genotype-phenotype correlation with Caucasians from other regions of the world and between FAP patients with and without detectable APC mutations. METHODS: We screened 242 members from 57 unrelated FAP families using a combination of cDNA protein truncation test, multiplex ligation-dependent probe amplification, and differential expression techniques. RESULTS: APC germline mutations were detected in 50 families. In contrast to Caucasians, fundic gland polyposis in Singapore patients was associated with APC mutations throughout the coding region and osteomas were also not confined to codon 767-1573. There was also no FAP-associated hepatoblastoma or medullablastoma. APC mutation-negative patients from four families with mixed (adenomatous/hyperplastic/atypical juvenile) polyps were subsequently reclassified as hereditary mixed polyposis syndrome (HMPS) patients. APC mutation-negative patients with classical adenomatous polyposis were negative for MYH, beta-catenin, and Axin 1 mutations. These patients had a significantly older age at diagnosis (P < 0.001) and more colorectal cancers (P= 0.017) than patients with APC mutations. CONCLUSIONS: We achieved a 94% (50/53) APC mutation detection rate via a combination of techniques, suggesting that the current detection rate is probably not exhaustive. Singapore patients have some features similar to and other features distinct from Caucasians. Furthermore, APC mutation-negative patients have accelerated cancer progression that merits closer surveillance.     

Desmoid tumours in familial adenomatous polyposis.

Desmoids are rare, benign fibromatous lesions, which can arise in patients with familial adenomatous polyposis (FAP), a disorder caused by germline adenomatous polyposis coli (APC) gene mutation. This study investigated the risk of desmoids in FAP, the relation between specific APC gene mutations and desmoid formation, and the clinical characteristics of FAP patients with desmoids. Eighty three of 825 FAP patients (10%) from 49 of 161 kindreds (30%) had desmoids. The absolute risk of desmoids in FAP patients was 2.56/1000 person years; comparative risk was 852 times the general population. APC gene mutations were similar in families with and without desmoids. The female/male ratio was 1.4 (p = NS). Previous abdominal surgery was noted in 68% of patients with abdominal desmoids (55% developed within five years postoperatively). Desmoid risk in FAP family members of a desmoid patient was 25% in first degree relatives v 8% in third degree relatives. Desmoids are a comparatively common complication of FAP associated with surgical trauma and familial aggregation. Desmoid development was not linked to specific APC gene mutations and was not found predominantly in women. Studies of chemopreventive therapy, given within five years after abdominal surgery, should be considered in FAP patients with a family history of desmoid disease.     

Germline and somatic mutations in exon 15 of the APC gene and K-ras mutations in duodenal adenomas in patients with familial adenomatous polyposis.

BACKGROUND: In sporadic colorectal adenomas mutations in the adenomatous polyposis gene (APC) are among the first gene aberrations to appear. In familial adenomatous polyposis (FAP) the patients already have a germline mutation in the APC gene. To investigate the natural history of duodenal adenomas in FAP patients, we examined germline and somatic mutations of the APC gene and K-ras mutations in these lesions. METHODS: Frozen sections from 54 duodenal polyps from 31 FAP patients were used to histologically verify the presence of adenomatous growth in the mucosa; the rest of each biopsy specimen was processed for DNA extraction. APC exon 15 was investigated with the protein truncation test (PTT), using four overlapping polymerase chain reaction (PCR) fragments, and samples showing an APC mutation were thereafter sequenced. The adenomas were examined for K-ras mutations by use of a combination of the 'enriched PCR method' and temporal temperature gradient electrophoresis. RESULTS: APC germline mutations in exon 15 were found in 19 of 31 (61%) patients, whereas somatic mutations were localized to 12 of 54 (22%) duodenal adenomas. In seven adenomas both the germline and the somatic mutations were found, whereas five small adenomas showed somatic mutations only. There was no tendency for more mutations to be detected in large and severely dysplastic adenomas compared with small and mildly dysplastic ones. K-ras mutations were found in four (7%) duodenal adenomas. CONCLUSIONS: The low rate of somatic APC and K-ras mutations in duodenal adenomas may indicate another neoplastic pathway than in FAP adenomas of the large bowel, or that a modifier gene is cosegregating with the disease.     

Can APC mutation analysis contribute to therapeutic decisions in familial adenomatous polyposis? Experience from 680 FAP families

BACKGROUND AND AIMS: In familial adenomatous polyposis (FAP), correlations between site of mutation in the adenomatous polyposis coli (APC) gene and severity of colonic polyposis or extracolonic manifestations are well known. While mutation analysis is important for predictive diagnosis in persons at risk, its relevance for clinical management of individual patients is open to question. METHODS: We examined 680 unrelated FAP families for germline mutations in the APC gene. Clinical information was obtained from 1256 patients. RESULTS: APC mutations were detected in 48% (327/680) of families. Age at diagnosis of FAP based on bowel symptoms and age at diagnosis of colorectal cancer in untreated patients were used as indicators of the severity of the natural course of the disease. A germline mutation was detected in 230 of 404 patients who were diagnosed after onset of bowel symptoms (rectal bleeding, abdominal pain, diarrhoea). When these patients were grouped according to the different sites of mutations, mean values for age at onset of disease differed significantly: patients carrying APC mutations at codon 1309 showed a disease onset 10 years earlier (mean age 20 years) compared with patients with mutations between codons 168 and 1580 (except codon 1309) (mean age 30 years), whereas patients with mutations at the 5' end of codon 168 or the 3' end of codon 1580 were diagnosed at a mean age of 52 years. Within each group of patients however large phenotypic variation was observed, even among patients with identical germline mutations. A higher incidence of desmoids was found in patients with mutations between codons 1445 and 1580 compared with mutations at other sites, while no correlation between site of mutation and presence of duodenal adenomas was observed. CONCLUSIONS: As age at manifestation and course of the disease may be rather variable, even in carriers of identical germline mutations, therapeutic decisions should be based on colonoscopic findings in individual patients rather than on the site of mutation. However, in patients with mutations within codons 1445-1580, it may be advisable to postpone elective colectomy because desmoids may arise through surgical intervention.     

An unexpected Cowden syndrome case found among members of a large familial adenomatous polyposis kindred

Genetic testing is now considered the standard of care in the management of familial adenomatous polyposis (FAP). Non-carriers of mutations are excluded from endoscopic surveillance. During the systematic screening of the relatives of an affected member with FAP, one non-carrier of APC mutations was unexpectedly found with the typical Cowden syndrome phenotype. One large Algerian family with FAP was screened for an APC germline mutation. Moreover, we also performed a mutation search in the Cowden syndrome member for PTEN, BMPR1A or MADH4 (SMAD4) germline mutations. We identified a mutation in the APC gene that results in a truncated protein (Y935X) in the FAP proband, and subsequently in 12 FAP-affected members. Among the 12 APC mutation-negative members of this family, we found one member with the Cowden disease phenotype. However, the mutation analysis in the PTEN gene and the two other genes involved in juvenile polyposis, namely BMPR1A and MADH4 (SMAD4), in the Cowden syndrome patient failed to show any pathogenic mutation. Genetic testing is a powerful tool that can provide a definitive diagnosis for FAP. However, not all polyposes in the FAP family are adenomatous polyposes.     

Preliminary results of the molecular diagnosis of familial adenomatous polyposis in Cuban families

BACKGROUND AND AIMS: Familial adenomatous polyposis (FAP) is an autosomal dominant condition characterized by multiple adenomatous polyps in the colon and rectum that inevitably develop into adenocarcinomas if the patient's colon is not removed in time. To date more than 500 mutations related to the disease have been identified in the APC (adenomatous polyposis coli) gene. The molecular study of FAP families was initially introduced in Cuba with the aim of identifying the asymptomatic carriers of APC gene mutations in each family. PATIENTS AND METHODS: We studied 23 individuals from 17 Cuban families who had been diagnosed clinically with FAP. Peripheral DNA was extracted from the index case of each family. Exon 15 of the APC gene was screened for germinal mutations using PCR and DNA heteroduplex. RESULTS: Three different germinal mutations were identified in the mutational clustering region of APC gene by sequencing analysis in five FAP unrelated families. Three families carry the most frequent mutation in APC in codon 1309, while the other two families carry mutations in codons 1061 and 1192, respectively. Two asymptomatic carriers of one family were detected, and later the disease was confirmed by colonoscopy in a very early stage while six members at risk were found to be negative. CONCLUSION: For the first time in Cuba molecular diagnosis of FAP was performed and the development of colorectal cancer prevented in asymptomatic carriers.     

Phenotypic differences in familial adenomatous polyposis based on APC gene mutation status

Background—Familial adenomatous polyposis(FAP) is a clinically well defined hereditary disease caused bygermline mutations within the adenomatous polyposis coli (APC) gene.Although several techniques are applied in the mutation analysis of FAPkindreds about 20-50% of cases remain unclear, with no APC mutationidentified (APC negative).
Aims—To delineate phenotypic differences betweenAPC positive and APC negative patients with respect to colonic andextracolonic disease in order to determine whether additionalmechanisms are involved in the pathogenesis of FAP.
Methods—The entire coding region of the APC genewas analysed using single stranded conformation polymorphism andprotein truncation tests in 50 Swiss FAP families with a total of 161affected individuals. Differences in phenotypic manifestation werestatistically evaluated by Student's t test, Fisher'sexact test, and χ² test.
Results—Thirty six families (72%) were APCpositive. Statistically significant differences between APC positiveand APC negative groups were found for the mean age at diagnosis ofcolonic polyposis (35.2 versus 45.3 years, respectively) and for theoccurrence of stomach polyps (14 patients, all APC positive).Additionally, APC negative patients displayed lower polyp numbers atdiagnosis and less extracolonic manifestations.
Conclusions—FAP kindreds without detected APCgene mutations present with a notably milder disease phenotype comparedwith APC positive families, suggesting that different genetic factors might be involved.

Keywords:familial adenomatous polyposis; adenomatouspolyposis coli gene; mutation; colorectal cancer; extracolonicmanifestations

     

Familial adenomatous polyposis: more evidence for disease diversity and genetic heterogeneity

Familial adenomatous polyposis (FAP) is characterised by the presence of profuse colonic carpeting of adenomas throughout the entire colon and rectum. The genetic basis of FAP has been shown to be primarily associated with germline mutations in the APC gene. Notwithstanding, several reports have been published indicating that there is genetic heterogeneity in FAP and that the most likely explanation is the existence of another gene. In this report we further delineate the genotype/phenotype correlation in families that harbour germline mutations in the APC gene and identify some previously unreported changes in the APC gene which predispose to an attenuated disease phenotype. From 53 index patients diagnosed with either FAP or attenuated FAP, 27 harboured changes in the APC gene. The remaining 26 patients were further subgrouped according to their colonic phenotype. There were nine patients with a mixed hyperplastic/adenomatous colonic phenotype and there were 17 patients with an adenomatous colonic phenotype. Evaluation of the disease characteristics of these patients and their families is presented which may aid in the identification of new genes associated with colonic polyposis.     

Familial adenomatous polyposis patients without an identified APC germline mutation have a severe phenotype

BACKGROUND: Development of more than 100 colorectal adenomas is diagnostic of the dominantly inherited autosomal disease familial adenomatous polyposis (FAP). Germline mutations can be identified in the adenomatous polyposis coli (APC) gene in approximately 80% of patients. The APC protein comprises several regions and domains for interaction with other proteins, and specific clinical manifestations are associated with the mutation assignment to one of these regions or domains. AIMS: The phenotype in patients without an identified causative APC mutation was compared with the phenotype in patients with a known APC mutation and with the phenotypes characteristic of patients with mutations in specific APC regions and domains. PATIENTS: Data on 121 FAP probands and 149 call up patients from 70 different families were extracted from the Danish Polyposis register. METHODS: Differences in 16 clinical manifestations were analysed according to the patient's mutational status. Two sided independent t sample test, two sided chi(2) test, and odds ratios were calculated. RESULTS: Patients without identified APC mutations had a unique and severe phenotype, which was roughly described as: young age at diagnosis and subsequent death in spite of development of few colorectal adenomas; low risk of involvement of the upper gastrointestinal tract, as reflected by a low mean Spigelman stage, and a low risk of fundic gland polyposis. Finally, they had significantly fewer affected family members, although they do not themselves more often represent an isolated case. CONCLUSIONS: The severe phenotype should be considered when counselling FAP families in which attenuated FAP is excluded and in which a causative APC mutation has not been identified.     

Presymptomatic diagnosis of familial adenomatous polyposis coli

Familial adenomatous polyposis (FAP), an autosomal dominant inherited disease, confers a high risk of colon cancer, and recently the gene responsible for FAP, termed adenomatous polyposis coli (APC) gene, was identified and fully characterized. PURPOSE: For the presymptomatic diagnosis of FAP, we have performed linkage studies using two polymorphic systems close to or at the APC locus; cytosine-adenine dinucleotide repeat length polymorphism and restriction endonuclease RsaI site polymorphism. METHODS and RESULTS: Based on the two polymorphic systems, we have determined the haplotype at the APC locus in 23 individuals of two Korean families with FAP. From these haplotypes of individuals, we could make the diagnosis, whether affected or unaffected, in 74 percent of 31 at-risk persons. To decrease the chance of misdiagnosis caused by recombinant events, the use of haplotypes was better than using one polymorphic system. In addition to polymorphic analysis, we have also searched germline mutations of the APC gene in eight individuals (26 percent of all 31 at risk persons) of another two FAP families which could not be diagnosed definitely by linkage analysis. A 5 base-pairs deletion at codon 1309 was detected in one of the families, and a 5 base-pairs deletion at codon 1185 was also identified in another family by using a ribonuclease protection assay followed by DNA sequencing. From these results, we could diagnose FAP with 100 percent accuracy. CONCLUSION: Linkage studies by the Rsa I site polymorphism and cytosine-adenine repeat length polymorphism as well as the polymerase chain reaction-based sequencing method provide accurate and efficient tools for presymptomatic diagnosis of FAP in their families.Supported in part by a grant from the Seoul National University Hospital Research Fund (04-93-007) and a grant from Korea Science and Engineering Foundation (KOSEF-SRC-56-CRC-8).Read at the meeting of The American Society of Colon and Rectal Surgeons, Chicago, Illinois, May 2 to 7, 1993.     

Novel Germline APC Mutations in Swedish Patients with Familial Adenomatous Polyposis and Gardner Syndrome

Background: Familial adenomatous polyposis (FAP) is a familial cancer syndrome in which affected individuals develop multiple adenomatous polyps and are thereby at greatly increased risk of developing colorectal cancer. Gardner syndrome is a variant of FAP, in which the patients also develop extraintestinal tumors, in particular osteomas and desmoid tumors. An attenuated form of the disease (AFAP) is associated with fewer polyps, but still a high risk for colorectal cancer. Germline mutations in the adenomatosis polyposis coli (APC) gene cause FAP and Gardner syndrome and have recently been associated also with the development of AFAP. Methods: We have analysed the entire APC gene for germline mutations in 7 patients with FAP and in 6 patients with suspected AFAP. Mutation screening was performed by direct sequencing of exons 1-14 and using the protein truncation test for analysis of exon 15. Results: Novel disease-causing germline mutations, all of which resulted in truncation of the APC protein, were identified in 6 of the 7 patients with FAP or Gardner syndrome. No APC mutation was detected in any of the 6 patients with suspected AFAP. Conclusions: This study reports novel FAP- and Gardner syndrome-causing mutations in the APC gene. The lack of APC mutations in patients with multiple polyps at young age indicates that other genetic defects may cause this phenotype.     

Novel germline APC mutations in Swedish patients with familial adenomatous polyposis and Gardner syndrome

BACKGROUND: Familial adenomatous polyposis (FAP) is a familial cancer syndrome in which affected individuals develop multiple adenomatous polyps and are thereby at greatly increased risk of developing colorectal cancer. Gardner syndrome is a variant of FAP, in which the patients also develop extraintestinal tumors, in particular osteomas and desmoid tumors. An attenuated form of the disease (AFAP) is associated with fewer polyps, but still a high risk for colorectal cancer. Germline mutations in the adenomatosis polyposis coli (APC) gene cause FAP and Gardner syndrome and have recently been associated also with the development of AFAP. METHODS: We have analysed the entire APC gene for germline mutations in 7 patients with FAP and in 6 patients with suspected AFAP. Mutation screening was performed by direct sequencing of exons 1-14 and using the protein truncation test for analysis of exon 15. RESULTS: Novel disease-causing germline mutations, all of which resulted in truncation of the APC protein, were identified in 6 of the 7 patients with FAP or Gardner syndrome. No APC mutation was detected in any of the 6 patients with suspected AFAP. CONCLUSIONS: This study reports novel FAP- and Gardner syndrome-causing mutations in the APC gene. The lack of APC mutations in patients with multiple polyps at young age indicates that other genetic defects may cause this phenotype.     

五个家族性腺瘤性息肉病家系分析

目的分析5个家族性腺瘤性息肉病（FAP）家系,总结常染色体显性遗传规律。 方法对5个FAP家系进行调查分析,取外周血、粪便行全外显子组测序（WES）筛查大肠癌基因,行结肠镜检查并取活体组织进行病理分析。 结果5个家系中,连续几代发生FAP,当父亲或者母亲患FAP后,其子代发生FAP的概率均等（50%）,无性别差异,发病者均存在腺瘤样结肠息肉病基因（APC）突变,未成年人中未见发病,部分患者患有2种以上肿瘤。 结论在有FAP病史的家系中,未成年人一般不发病,成年后均需要进行APC基因检测及结肠镜检查,一旦发现腺瘤需要尽早进行内镜下治疗,避免结直肠癌的发生。     

Multiple desmoid tumors in a patient with familial adenomatous polyposis caused by the novel W421X mutation

Familial adenomatous polyposis (FAP) is a rare syndrome characterized by the presence of hundreds to thousands of colorectal adenomas and is responsible for less than 1% of all colorectal cancers. The syndrome is also characterized by extra-colorectal features including amongst others upper gastrointestinal tract polyps and desmoid tumors. The syndrome is inherited by an autosomal dominant gene, the adenomatous polyposis coli (APC) gene. We present the physical history, clinical presentation, diagnosis and treatment of a patient with a novel germline APC mutation, the W421X mutation, which resulted in FAP presenting with about a hundred colorectal polyps, gastric hyperplastic polyps and multiple aggressive intra-abdominal and extra-abdominal desmoid tumors.     

Familial adenomatous polyposis: genetics and epidemiology

Familial adenomatous polyposis (FAP) is a rare genetic disease characterised by the development of hundreds to thousands of adenomatous polyps along the colon-rectum leading to cancer at a young age, if left untreated. In 1991, the gene responsible for the vast majority of FAP cases, the adenomatous polyposis coli (APC) gene, was identified. In 5-30% of FAP patients, no APC mutation is identifiable by current genetic testing. In 2003, it was shown that 'APC-negative' FAP patients may carry biallelic mutations in a different gene, the MYH gene. Genetics of FAP will be discussed in relation to its present clinical applications. If the hereditable mutation(s) is/are known in a family, it is possible to plan endoscopic surveillance only for those who actually inherited the mutation(s). Also, genetic testing may be of help in the diagnosis of atypical adenomatous polyposis cases and in the clinical management of affected individuals.     

Hepatocellular adenoma displaying a HNF1alpha inactivation in a patient with familial adenomatous polyposis coli

Patients with familial adenomatous polyposis coli (FAP) may rarely develop hepatocellular adenoma. Here we report the case of a 37-year-old FAP woman presenting a hepatocellular adenoma after oestroprogestative oral contraception use. In this steatotic adenoma, we identified an inactivating biallelic mutation of HNF1alpha. In addition to the known germline APC mutation Q1062fs, we did not find an inactivation of the second APC allele nor an activation of the beta-catenin target genes GLUL and GPR49. Our findings contrast with two hepatocellular adenoma cases related to FAP, for which a biallelic inactivation of the APC gene was previously described. Altogether, these results suggest that benign hepatocellular carcinogenesis may be dependent on or independent of the Wnt/beta-catenin pathway in patients with FAP.