Features of Patients With Hereditary Mixed Polyposis Syndrome Caused by Duplication of GREM1 and Implications for Screening and Surveillance

Hereditary mixed polyposis syndrome is a rare colon cancer predisposition syndrome caused by a duplication of a noncoding sequence near the gremlin 1, DAN family BMP antagonist gene (GREM1) originally described in Ashkenazi Jews. Few families with GREM1 duplications have been described, so there are many questions about detection and management. We report 4 extended families with the duplication near GREM1 previously found in Ashkenazi Jews; 3 families were identified at cancer genetic clinics in Israel and 1 family was identified in a cohort of patients with familial colorectal cancer. Their clinical features include extracolonic tumors, onset of polyps in adolescence, and rapid progression of some polyps to advanced adenomas. One family met diagnostic criteria for Lynch syndrome. Expansion of the hereditary mixed polyposis syndrome phenotype can inform surveillance strategies for carriers of GREM1 duplications.

Adenomatous Polyposis Coli, mismatch repair, and microsatellite instability in colorectal cancer based on different locations

AIM

to examine the protein expression negative (PEN) of Adenomatous Polyposis Coli (APC), Mismatch Repair (MMR), and Microsatellite Instability (MSI) status of colorectal cancer (CRC), and establish a comparison of those molecular characteristics in CRC location among Indonesian patients in Adam Malik Hospital, Pirngadi Hospital, and other hospitals within the network of Faculty of Medicine University of Sumatera Utara Medan Indonesia.

METHODS

this prospective study was conducted from April to December 2012. Fresh tissues were obtained from colorectal tumor patients. The APC-PEN, MMR (MLH1, MSH2, PMS2, MSH6)-PEN, were assessed by immunohistochemistry, and MSI by PCR using 5 microsatellite markers (BAT25, BAT26, D2S123, D5S346, D17S250), as independent variables. The tumour locations as dependent variables were divided into proximal colon (caecum, ascending colon, transverse colon); distal colon (splenic flexure, descending colon, sigmoid) and rectum. The comparative study were done by bivariate and multivariate analysis.

RESULTS

there were 77 cases of colorectal adenocarsinoma. MMR-PEN was found in 54 of 77 (70.1%). MLH1-PEN was different between distal colon and rectal cancer (p=0.008); MSH6-PEN was different between proximal colon and rectal cancer (p= 0.020). Multivariate analysis showed: MLH1-PEN was related to cancer location (p=0.006) with OR 0.12 (95% CI 0.026-0.547). It had 0.12 times probability to be found in distal than rectum. MLH1-PEN had 10 times higher probability to be found in proximal than in distal (p=0.037). MSH6-PEN was related to the location (p=0.026) with OR 0.165 (95% CI 0.034-0.803), and had 0.165 times probability to be found in proximal than rectum; and 11 times higher probability in distal than proximal colon (p=0.043). APC-PEN was related to the location (p=0.020), with OR 6.897 (95% CI 1.359-34.995), and 6.89 times higher probability in distal than in rectum, with other variables controlled. MSI-H was found in 29 of 77 (37.7%) and MSI-L/MSS in 48 (62.3%). The proportion of MSI-H displayed a tendency to occur in proximal rather than in distal colon or rectal cancer.

CONCLUSION

the underlying carcinogenic pathway or molecular background differs according to the cancer locations of CRC patients in this region. MLH1-PEN was prominent in proximal colon cancer, MSH6-PEN in distal colon and rectal cancer, and APC-PEN in distal colon respectively.

Racial differences in measures of obesity and risk of colon adenoma

Obesity is an established risk factor for several malignancies. However, the specific measurement of obesity most relevant to colon neoplasia is still debated, and evidence has suggested gender and racial differences in this measurement. In this study, we sought to compare which measurement--BMI, waist circumference (WC), waist-to-hip ratio (WHR) or waist-to-height ratio (WHtR)--is most strongly associated with development of colon adenomas, a precursor of colon cancer, and to investigate differences in this association between racial groups. We confirmed the strong association between WHR, as a measure of central obesity, and development of colon neoplasia. In our overall analysis, patients in the highest WHR quartile showed a substantial increase in risk of colon adenomas compared to patients in the lowest WHR quartile (odds ratio (OR) = 1.82, 95% confidence interval (CI): 1.12-2.71, P(trend) = 0.0017). In stratified analyses, we noted that strongly associated obesity measures in European Americans were WC (OR = 2.38, 95% CI = 1.45-3.92, P(trend) = 0.0004) and BMI (OR = 2.18, 95% CI = 1.37-3.49, P(trend) = 0.0015), whereas in African Americans, WHR was the strongest and the only obesity measure statistically significantly associated with adenoma risk (OR = 2.12, 95% CI = 1.05-4.30, P(trend) = 0.025). Our data highlight the importance of obesity in the development of early colon neoplasia and suggest substantial racial differences in the measures of obesity most strongly associated with risk of colon adenomas.

Proximal shift in the distribution of adenomatous polyps in Korea over the past ten years

BACKGROUND/AIMS

Several reports have suggested a trend of right-side shift of colorectal cancer; however, there were only a few studies on the chronologic changes in the distribution of adenomatous polyps. We aimed to study the changes in the distribution of colorectal adenomatous polyps over the past ten years.

METHODOLOGY

We reviewed medical records of patients who underwent a colonoscopy at Yonsei University Severance Hospital, Seoul, Korea between January 1996 and December 2005. Patients who had an adenomatous polyp with a diameter of at least 5mm were included. Of these, patients with a history of colon resection, colorectal cancer, colorectal polyp, inflammatory bowel disease, HNPCC, or familial adenomatous polyposis were excluded.

RESULTS

A total of 2,498 patients and 4,591 adenomatous polyps were included in this study. Analysis with respect to number of patients showed significant increases in the proportion of patients with adenomatous polyp on the proximal colon, from 48.5% to 66.3% (p<0.001). Analysis with respect to number of polyps revealed that the proportion of adenomatous polyps on the proximal colon significantly increased from 48.9% to 62.3% (p<0.001).

CONCLUSIONS

The proportion of adenomatous polyp on the proximal colon significantly increased over the past 10 years.

First genetic analysis in Tunisian familial adenomatous polyposis probands

Familial adenomatous polyposis (FAP) is an autosomal dominant inherited disease characterized by the development of hundreds to thousands of adenomatous polyps in colon and rectum. The APC gene (adenomatous polyposis coli) is considered as the major mutated gene in FAP. It has been shown that biallelic germline mutations in the base-excision-repair gene MYH can be responsible for a recessive inheritance of adenomatous polyposis (AP). This study is the first Tunisian genetic analysis on AP patients. Multiplex ligation-dependent probe amplification (MLPA) was used to screen the APC gene for large genomic rearrangements. The total APC and MYH exon sequences and exon-intron edges were sequenced in an effort to detect germline mutations, four were explored. Mutations were detected in four patients that fulfil the clinical criteria of AP. Three mutations were found in the APC gene, of which two were novel (c.1636_1639delAGTG and c.2514 G>T) and all gave rise to a truncated APC protein. The missense G382D mutation, already described in north and south European populations was found in the MYH gene at the homozygous state in the fourth patient with moderate AP. Our preliminary study provides a basis for implementation of genetic counselling for AP.

Clinical features of familial adenomas polyps in Chinese and establishment of its immortal lymphocyte cell lines

AIM: To reserve the rare Chinese familial adenomas polyp (FAP) family resource and to investigate the clinical features of FAP in Chinese for its diagnosis.

METHODS: Clinical features of patients with FAP were investigated. If there is any question, their medical records were verified. Blood sample was taken and lymphocyte immortal cell lines were established with modified EB-transformation methods. Congenital hypertrophy of retinal pigment epithelium (CHRPE) was checked by an experienced ophthalmologist.

RESULTS: Twenty seven families including 21 classical FAP (CFAP) families, 3 attenuated FAP (AFAP) families, and 3 suspected AFAP families were investigated. A total of 116 lymphocyte immortal cell lines were established from 26 families. In all the FAP families, colorectal cancer occurred at the mean age of 42.84 years. Of the 16 families checked, 15 (93.75%) had CHRPE. The mean number of patients suffering from colorectal neoplasm was 3.14 in CFAP families and 2.0 in AFAP families (P < 0.01). The mean oldest age at diagnosis of FAP was 41.75 years in CFAP families, and 58.67 years in AFAP families, respectively (P < 0.01). Mean age of development of colorectal cancer was 42.23 in CFAP and 57.33 years old in AFAP (P < 0.01). Mean of the earliest age at diagnosis of FAP was 29.95 years in the FAP families with a positive family history and 46.80 years in the FAP families with a negative family history (P < 0.01). The ratio of extra-intestinal tumors to colorectal neoplasms was different in the two kinds of families with positive and negative family history (P < 0.01).

CONCLUSION: Additional use of ciclosporin will effectively improve to establish lymphocyte immortal cell lines with modified EB- transformation methods. In Chinese FAP, there was a high frequency of CHRPE , and a later age at diagnosis and a later age of development of colorectal cancer in AFAP. And earlier age at diagnosis in FAP with positive family history was also found that will help to diagnose various kinds of FAP in Chinese.

Juvenile Polyp in Thai Children—Clinical and Colonoscopic Presentation

BACKGROUND

The aim of this prospective study was to describe the clinical characteristics of colorectal polyp in Thai children.

METHODS

From December 2002 to February 2005, children under 15 years of age presenting with rectal bleeding were prospectively enrolled. Demographic, clinical, and laboratory information was recorded. Location, number, characteristics, and histopathology of the polyps were noted.

RESULTS

There were 32 patients with a mean age of 6.5 years. The most common presenting symptom was hematochezia, followed by prolapsing rectal mass and diarrhea. In 20 patients there was a single polyp, 6 had 2-4 polyps, and 6 were diagnosed with polyposis coli. Most of the polyps were located exclusively at the rectum and sigmoid colon. In only 7 cases were the polyps proximal to the rectosigmoid region. This included 6 patients who had polyps beyond the splenic flexure. All were juvenile polyps without evidence of adenomatous changes. Compared to those with isolated polyps, the patients with polyposis coli had a statistically significant incidence of right-sided polyps (P <0.001) and a history of prolapse of the rectal mass (P = 0.006).

CONCLUSIONS

Because of the high prevalence of right-sided polyps and the concern about malignant transformation, colonoscopy should be considered as the initial evaluation in children with rectal bleeding.

Mesenteric desmoid tumors in Singapore familial adenomatous polyposis patients: clinical course and genetic profile in a predominantly Chinese population

PURPOSE

This study examined the mutational profile of the adenomatous polyposis coli gene in relation to the development of desmoid tumors in familial adenomatous polyposis patients from a predominantly Chinese population.

METHODS

This is a retrospective review of all patients with familial adenomatous polyposis coli from the Singapore Polyposis Registry. Identification of specific adenomatous polyposis coli gene mutation was performed and clinical course of associated desmoid disease obtained from case records and a computerized database.

RESULTS

Two hundred five patients from 75 families afflicted with familial adenomatous polyposis coli were reviewed, with gene mutations identified in 107 patients. Of these, 23 (11.2 percent) developed desmoids. The male-to-female ratio was 1:1.3 and the ethnic distribution was Chinese (n=17) and Malay (n=6). Of the 92 patients with mutations 5' to codon 1444, 11 patients (12 percent) developed desmoids compared with 6 of 15 (40 percent) patients with adenomatous polyposis coli gene mutations 3' to codon 1444 (P<0.01). The clinical course of desmoid tumors can be divided into stable (n=11), variable (n=3), progressive (n=6), and aggressive growth (n=3). Only 3 (13 percent) patients with aggressive tumor growth required chemotherapy. There was no correlation between the site of mutation and the clinical progression of the desmoids. Seventy-four percent of these desmoids (17/23) developed at a mean interval of 2.98 years after restorative proctocolectomy, while only 30 percent (7/23) were diagnosed preoperatively or discovered during the initial surgery. The most common complications related to the mesenteric desmoids were intestinal obstruction (21.7 percent), ureteric obstruction (17.4 percent), and encasement of superior mesenteric vessels (13 percent).

CONCLUSION

The clinical course of desmoids in an individual familial adenomatous polyposis patient remains unpredictable and no reliable genetic marker is available for prognostication in desmoid disease.

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.

CT colonography in a Korean population with a high residue diet: Comparison between wet and dry preparations

AIM

To compare wet and dry preparation methods for computed tomography colonography (CTC) in terms of preparation quality, interpretation time, and diagnostic performance for polyp detection in a population with a high residue diet.

MATERIALS AND METHODS

Eighty-six patients were divided into two groups. Group 1 (n=24) received a wet preparation of 4l polyethylene glycol (PEG) solution, and group 2 (n=62) received a dry preparation of phosphor-soda. Abnormal findings, including polyps, and the time required to interpret the CTC images in both groups were documented by a radiologist. CTC findings were compared to those of colonoscopy as a reference standard. Two radiologists evaluated the quality of CTC with regard to residual fluid, faeces, and colonic distension using a four-point scale in consensus. Statistical differences for residual fluid, faeces, distensibility on CTC, and interpretation time between the two groups were analysed. The diagnostic performance of CTC in both groups was also compared.

RESULTS

One-hundred and ninety polyps in 70 patients were identified using colonoscopy. Regarding the quality of images produced the wet preparation was significantly better than the dry preparation (p<0.05). The average interpretation time was significantly shorter for the wet group (11.7 min) than the dry group (16.4 min) (p<0.05). For per-patient analysis, the positive predictive value (PPV) was significantly better for the wet (100%) than the dry group (79.6%; p=0.025). Sensitivities and PPV for >or=10 mm polyps were comparable between two groups (p>0.05).

CONCLUSION

In a population with a high-residue diet, CTC with wet preparation can be interpreted in a time-efficient manner and is comparable with CTC with dry preparation.

Racial and gender disparities in hereditary colorectal cancer risk assessment: the role of family history

BACKGROUND

In this study, we aimed to examine racial/ethnic and gender differences in self-reported family cancer history knowledge in patients at high risk for hereditary colon cancer syndromes.

METHODS

We performed retrospective analysis of all referrals to the University of Chicago High Risk Colon Cancer Clinic between 1995 and 2003.

RESULTS

We found hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis in 17% and 9% of Whites, respectively, and 6% and 0% of Blacks, respectively. Unknown paternal history was found in 6.5% of Whites and 18.9% of Blacks (23% men, 11% women).

CONCLUSIONS

Blacks and men had significantly decreased rates of paternal history cancer knowledge.

Mutation analysis of the adenomatous polyposis coli (APC) gene in Danish patients with familial adenomatous polyposis (FAP)

Development of one hundred or more adenomas in the colon and rectum is diagnostic for the dominantly inherited, autosomal disease Familial Adenomatous Polyposis (FAP). It is possible to identify a mutation in the Adenomatous Polyposis Coli (APC) gene in approximately 80% of the patients, and almost 1,000 different pathogenic mutations have been identified in the APC gene up till now. We report 12 novel and 24' previously described germline APC mutations from 48 unrelated Danish families. Four families with the mutation localized in the 3' region of the gene showed great variance in phenotypic presentation.

Genetic anthropology of the colorectal cancer-susceptibility allele APC I1307K: evidence of genetic drift within the Ashkenazim

The adenomatous polyposis coli (APC) I1307K allele is found in 6% of the Ashkenazi Jewish population and in 1%-2% of Sephardi Jews; it confers a relative risk of 1.5-2.0 for colorectal cancer (CRC) on all carriers. Within the Ashkenazim, the existence of numerous high-prevalence mutations, including I1307K, has sparked controversy over whether genetic drift or selection is the underlying cause. For the present population-based case-control study of CRC in Israel, we tested whether selection has operated at I1307K. We also estimated the age of the I1307K allele, to understand its origin in the context of the Jewish diasporas and subsequent founder events. We genotyped 83 matched pairs, in which one or both members of the pair carried I1307K, at three microsatellites and two SNPs. Haplotypes were statistically constructed using PHASE software. Single-marker age estimates for I1307K were calculated using the approach described by Risch et al. A common progenitor haplotype spanned across APC I1307K from the centromeric marker D5S135 to the telomeric marker D5S346 and was observed in individuals of Ashkenazi, Sephardi, and Arab descent. The ancestor of modern I1307K alleles existed 87.9-118 generations ago ( approximately 2,200-2,950 years ago). This age estimate indicates that I1307K existed at about the time of the beginning of the Jewish diaspora, explaining its presence in non-Ashkenazi populations. Our data do not indicate that selection operated at I1307K (D5S346, P=.114; D5S135, P=.373), providing compelling evidence that the high frequency of disease-susceptibility alleles in the Ashkenazim is due to genetic drift, not selection. This research underscores the importance of the migratory patterns of ancestral populations in the ethnic and geographic distribution of APC I1307K.

Adenomatous polyposis coli gene as a gatekeeper

The Adenomatous Polyposis Coli (APC) Gene is a tumor suppressor gene located in the chromosome 5q21. It has a sequence of 2843 amino acids and a weight of 312 kD. The mutation of the APC gene occurs at the early stages of most sporadic colorectal cancers; and up to 30% in familial adenomatous polyposis. The absence of APC will indicate the inadequate migration of colon mucous cells and its accumulation resulting in polyps formation, which determines a stage in carcinogenicity. An adequate study in prone groups may lead to chemoprophylaxis and/or early treatment of polyps.

The I1307K APC polymorphism: prevalence in non-Ashkenazi Jews and evidence for a founder effect

A missense mutation within the APC gene, I1307K, was described in Ashkenazi individuals at risk for colorectal cancer (CRC) and in the general population. The anecdotal reporting of the occurrence of this mutation in some non-Ashkenazi individuals led us to hypothesize that within the Jewish people, the I1307K polymorphism may reflect a founder mutation, and that the mutation is not restricted to ethnic Ashkenazis. To test that notion, and to establish the occurrence rate of the I1307K polymorphism in non-Ashkenazi Jewish populations, we screened Iraqi and Moroccan Jews and consecutive Jewish CRC patients and performed haplotype analysis with APC-linked markers in two I1307K carrier families. We analyzed Jewish individuals: 210 Moroccans, 160 Iraqis, 148 Ashkenazi, and 349 CRC patients (227 Ashkenazi and 122 non-Ashkenazi). The mutation detection scheme included PCR followed by denaturing gradient gel electrophoresis (DGGE) or modified restriction analysis (MRA). Haplotypes were assessed using three intragenic and three flanking markers. The I1307K polymorphism was detected in 29/227 Ashkenazi (12.8%), 2/122 (1.6%) non-Ashkenazi CRC patients, and in 2 individuals each (approximately 1%) within the Moroccan and Iraqi populations. Allelic pattern analysis in all our I1307K carriers, revealed a common haplotype for the three intragenic markers tested, in all mutation carriers, regardless of ethnic origin. The I1307K polymorphism, therefore, exists in all ethnic Jewish populations: Ashkenazi and non-Ashkenazi, with or without colon cancer. Jewish I1307K mutation carriers share a common allelic pattern with APC-linked markers. This strongly supports the notion of a founder mutation for I1307K.

Congenital hypertrophy of the retinal pigment epithelium and APC mutations in Chinese with familial adenomatous polyposis

Mutations in the adenomatous polyposis coli gene (APC) often cause both congenital hypertrophy of the retinal pigment epithelium (CHRPE) and familial adenomatous polyposis (FAP). To investigate the relationship between APC mutations, CHRPE and FAP, all FAP patients at the Prince of Wales Hospital, Hong Kong, were asked to participate in a study. Ten Chinese patients from 6 kindreds and their family members volunteered, along with 12 healthy control subjects selected among hospital visitors and staff. All were examined for dilated fundus by indirect ophthalmoscopy. Mutations in APC coding exons were detected by sequencing. In one FAP patient, a novel A insertion at codon 1023 was detected. Three previously reported mutations were detected in 6 FAP patients: a deletion of ACAAA at codon 1061, and 2 truncating point substitutions at codons 216 and 283. In 3 FAP patients, no APC mutation was found, suggesting that mutations in APC coding regions are not the sole cause of FAP or CHRPE. A total of 64 CHRPE lesions were found in FAP patients and some relatives with and without APC mutations. Contrary to most reports, APC mutations before exon 9 did cause CHRPE lesions, albeit relatively few.

Adenomatous polyposis coli I1307K mutation in Jewish patients with different ethnicity: prevalence and phenotype

BACKGROUND

A new mutation, I1307K, recently was reported in the adenomatous polyposis coli (APC) gene. This mutation was found to be predominant in Ashkenazi Jews, creating a hypermutable area and predisposing the development of carcinoma. The objective of the current study was to estimate the prevalence of this mutation in several of the ethnic groups that comprise the Israeli population and to elucidate the clinical features of the mutation carriers with colorectal carcinoma (CRC).

METHODS

A total of 111 consecutive CRC patients were evaluated and their medical history and clinical data recorded. The general population (298 Ashkenazim and 189 Yemenites) also was tested for the presence of this mutation. Mutation screening was performed using both the polymerase chain reaction-based amplification refractory mutation system and a commercial APC kit.

RESULTS

Of the total of 111 CRC patients, 15 (13.5%) carried the I1307K mutation and 26 of 487 subjects from the general population (5.3%) carried the I1307K mutation (P = 0.004). Among the 71 Ashkenazi CRC patients there were 12 carriers (16.9%) whereas 17 of the 298 Ashkenazi Jewish general population (5.7%) carried the mutation (P = 0.004). Of the 4 CRC patients of Yemenite origin, 3 carried the mutation and 9 carriers were found among 189 subjects in the general Yemenite population (4.7%) (P = 0.0007). None of the 34 Sepharadic or 2 Arab CRC patients carried the APC I1307K allele. Late age at diagnosis (64.6 years +/- 10.0, which is similar to that of the noncarriers), mostly right-sided tumors, and moderate to good differentiation constituted the phenotype of the mutation carriers.

CONCLUSIONS

The authors believe the findings of the current study broaden the known spectrum of ethnic groups in which the APC I1307K mutation is prevalent. The phenotype of the mutation carrier CRC patients does not conform to the expected familial pattern of germline mutations. The phenotype and the differential incidence rate of CRC among APC I1307K carriers of various ethnic groups suggest low penetrance.

Germline mutations of the APC gene in Korean familial adenomatous polyposis patients

We extensively analyzed genomic DNA and messenger RNA (mRNA) from 62 unrelated Korean patients with familial adenomatous polyposis (FAP) for identification of germline adenomatous polyposis coli (APC) gene mutations. We adopted both single-strand conformation polymorphism (SSCP) analysis and a method of analysis involving the reverse transcription-polymerase chain reaction (RT-PCR) followed by a protein truncation test (PTT). DNA sequencing confirmed all alterations represented by aberrant bands. Germline mutations were identified in 38 patients (61%). Nineteen of the detected mutations were presumed to be novel, thus emphasizing the heterogeneity of the mutational spectrum in Korean FAP patients. In the initial 48 patients, SSCP analysis was followed by PTT for those patients for whom no detectable mutations were found by SSCP. Using this combined approach, we identified germline APC gene mutations in 29 of the 48 FAP patients (60%), including 6 patients in whom SSCP analysis failed to distinguish the mutant allele. In the 14 later patients, we identified truncating mutations in 9 patients (64%) using PTT only. Our results confirm that the mutation detection rate with PTT was superior to that with SSCP, and suggest that PTT would be a more practical screening method to detect germline mutations of the APC gene in FAP patients.