Turcot syndrome and its characteristic colonic manifestations

A case of Turcot's syndrome type 1 with loss of immunoexpression of MSH6 in colon cancer and liver metastasis due to secondary somatic mutation in coding mononucleotide (C)8 tract: a case report

BACKGROUND

Lynch syndrome (LS), which is known as a hereditary cancer syndrome, is distinguished by microsatellite instability, represented by the altered number of repetitive sequences in the coding and/or non-coding region. Immunohistochemical staining (IHC) of DNA mismatch repair (MMR) proteins (e.g., MLH1, MSH2, MSH6, and PMS2) has been recognized as an useful technique for screening of LS. Previous study has shown that the assessment of IHC, however, requires specific caution due to variable staining patterns even without germline mutations in MMR genes.

CASE PRESENTATION

A 48-year-old man, who had been treated for anaplastic astrocytoma, was referred to our department for the precise examination of progressing anemia. Whole-body examination revealed two advanced carcinomas in descending colon and stomach. A hypo-vascular mass lesion was detected in liver as well. Pathological diagnosis (on surgical specimens) was poorly differentiated adenocarcinoma in descending colon, moderately differentiated tubular adenocarcinoma in stomach, and liver metastasis, which is possibly from colon. It was suspected that this case would be Turcot's syndrome-type-1 due to its specific family history having two cases of colon cancer within the second relatives. Pathogenic frameshift mutations in codon 618 of MLH1 gene was identified. Immunohistochemical analyses (IHC) demonstrated complete loss of MLH1 immuno-expression as well as of PMS2 except for those in brain tumor. Although frameshift mutation was not found in MSH6 gene, histological expression of MSH6 was patchy in primary colon carcinoma and was completely lost in the metastatic site in liver. MSH6 expression in gastric carcinoma, a coincidental cancer in this case, was intact. An abnormal (C)8 region was identified by the cloned PCR of colon and liver tumors but not from gastric cancer. Frameshift mutation in a (C)8 tract in exon 5 of the MSH6 gene was also detected in liver metastasis.

CONCLUSION

This case supports a plausible mechanism, proposed by a previous literature, for the reduced expression of MSH6 in a somatic mutation manner, which might preferentially happen in colon cancer rather than in stomach carcinoma in MLH1/PMS2-deficient type of Turcot's syndrome type 1.

Biology of colorectal cancer

Colorectal cancer is a serious health problem, a challenge for research, and a model for studying the molecular mechanisms involved in its development. According to its incidence, this pathology manifests itself in three forms: family, hereditary, and most commonly sporadic, apparently not associated with any hereditary or familial factor. For the types having inheritance patterns and a family predisposition, the tumours develop through defined stages ranging from adenomatous lesions to the manifestation of a malignant tumour. It has been established that environmental and hereditary factors contribute to the development of colorectal cancer, as indicated by the accumulation of mutations in oncogenes, genes which suppress and repair DNA, signaling the existence of various pathways through which the appearance of tumours may occur. In the case of the suppressive and mutating tracks, these are characterised by genetic disorders related to the phenotypical changes of the morphological progression sequence in the adenoma/carcinoma. Moreover, alternate pathways through mutation in BRAF and KRAS genes are associated with the progression of polyps to cancer. This review surveys the research done at the cellular and molecular level aimed at finding specific alternative therapeutic targets for fighting colorectal cancer.

Familial adenomatous polyposis of the colon

Familial adenomatous polyposis (FAP) is a well-defined autosomal dominant predisposition to the development of polyposis in the colon and rectum at unusually early ages. The first symptoms of FAP are diarrhea and blood in the stool. Weight loss and weaknesses occur after the development of advanced tumour. The incidence of the FAP disorder is one per 10000 newborns. There are high levels of heterogeneity with regard to the number and timing of the occurrence of polyps. The classical form of FAP is characterized by the presence of more than 100 polyps, which appear in the second decade of life. The average time of occurrence of polyps is 15 years. The earliest symptoms of polyposis have been observed in a three-year-old child. The polyps are characterized by large potential for the development towards malignant tumour. Malignancy can occur from late childhood onwards. Attenuated adenomatous polyposis coli is characterized by a more benign course of disease in contrast to classical FAP. The occurrence of FAP is associated with mutations in the APC tumour suppressor gene, which was described in 1991. The APC gene is located on chromosome 5q21 and is involved in cell proliferation control. A recessive form of adenomatous polyposis is caused by mutations in the base excision repair gene - MUTYH gene. The MUTYH gene is involved in repairing DNA lesions as a result of oxidative DNA damage. MUTYH associated polyposis (MAP) is a predisposition to the development of polyps of the colon but the number of polyps is lower in comparison to classical FAP. The high risks of cancer observed in these two diseases make them important medical issues. Molecular studies of colonic polyposis have been performed in Poland for over fifteen years. A DNA Bank for Polish FAP patients was established at the Institute of Human Genetics in Poznan in which DNA samples from 600 FAP families have been collected.

Mutations of the Wnt antagonist AXIN2 (Conductin) result in TCF-dependent transcription in medulloblastomas

Medulloblastomas (MBs) represent the most common malignant brain tumors in children. Most MBs develop sporadically in the cerebellum, but their incidence is highly elevated in patients with familial adenomatous polyposis coli. These patients carry germline mutations in the APC tumor suppressor gene. APC is part of a multiprotein complex involved in the Wnt signaling pathway that controls the stability of beta-catenin, the central effector in this cascade. Previous genetic studies in MBs have identified mutations in genes coding for beta-catenin and its partners, APC and AXIN1, which cause activation of Wnt signaling. The pathway is negatively controlled by the tumor suppressor AXIN2 (Conductin), a scaffold protein of this signaling complex. To investigate whether alterations in AXIN2 may also be involved in the pathogenesis of sporadic MBs, we performed a mutational screening of the AXIN2 gene in 116 MB biopsy samples and 11 MB cell lines using single-strand conformation polymorphism and sequencing analysis. One MB displayed a somatic, tumor-specific 2 bp insertion in exon 5, leading to carboxy-terminal truncation of the AXIN2 protein. This tumor biopsy showed nuclear accumulation of beta-catenin protein, indicating an activation of Wnt signaling. In 2 further MB biopsies, mutations were identified in exon 5 (Glu408Lys) and exon 8 (Ser738Phe) of the AXIN2 gene, which are due to predicted germline mutations and rare polymorphisms. mRNA expression analysis in 22 MBs revealed reduced expression of AXIN2 mRNA compared to 8 fetal cerebellar tissues. Promoter hypermethylation could be ruled out as a major cause for transcriptional silencing by bisulfite sequencing. To study the functional role of AXIN2 in MBs, wild-type AXIN2 was overexpressed in MB cell lines in which the Wnt signaling pathway was activated by Wnt-3a. In this assay, AXIN2 inhibited Wnt signaling demonstrated in luciferase reporter assays. In contrast, overexpression of mutated AXIN2 with a deleted C-terminal DIX-domain resulted in an activation of the Wnt signaling pathway. These findings indicate that mutations of AXIN2 can lead to an oncogenic activation of the Wnt pathway in MBs.

Brain tumors in individuals with familial adenomatous polyposis: a cancer registry experience and pooled case report analysis

BACKGROUND

Most individuals with Familial Adenomatous Polyposis (FAP) harbor mutations in the APC gene on chromosome 5q21. They are at an increased risk of brain tumors, including cerebellar medulloblastoma, when compared with the general population (Brain Tumor Polyposis-BTP Type 2). Genotype-phenotype correlations between APC gene mutations and central nervous system (CNS) tumors have, thus far not been successful. Herein the authors have pooled their registry experience in BTP type 2 with the published reports.

METHODS

The authors analyzed their established hereditary CRC Registry for brain tumors in FAP pedigrees (56 families, 213 individuals), pooled their patients with BTP and known APC mutations with those reported thus far elsewhere, and compared the resulting mutation distribution of FAP-BTP with the mutation distribution for APC mutations in the US.

RESULTS

Twenty-eight patients from 24 families were accrued, the most common brain tumor in BTP was medulloblastoma (60%) predominantly in females (12:5) under the age of 20 (mean age 14.7 SD 9.2). Other histologic subtypes included astrocytoma and ependymoma. Analysis of the pooled APC mutation data by Chi-square test of association shows an odds ratio of 3.7 (P < .005) for all brain tumor subtypes and 13.1 (P < .001) for medulloblastoma in patients harboring segment 2 APC mutation (codons 679-1224) compared to nonsegment 2 mutation.

CONCLUSIONS

In patients with FAP and identifiable APC gene mutation, CNS tumors, especially medulloblastoma which developed in most cases during childhood, are more common in females with FAP and APC gene mutation in codons 686-1217. Further studies are necessary to determine if this observation and the natural history of medulloblastoma in children justifies novel, aggressive, targeted screening of at-risk individuals.

A homozygous mutation in MSH6 causes Turcot syndrome

Heterozygous mutations in one of the DNA mismatch repair genes cause hereditary nonpolyposis colorectal cancer (MIM114500). Turcot syndrome (MIM276300) has been described as the association of central nervous system malignant tumors and familial colorectal cancer and has been reported to be both a dominant and recessive disorder. Homozygous and compound heterozygous mutations in APC, MLH1, MSH2, and PMS2 genes have been reported in five families. Here we describe a nonconsanguineous Pakistani family, including a son with lymphoma and colorectal cancer diagnosed at ages 5 and 8, respectively, and an 8-year-old daughter with glioblastoma multiforme. Both children had features of neurofibromatosis type 1 including atypical café au lait spots and axillary freckling without a family history consistent with neurofibromatosis type 1, familial adenomatous polyposis, or hereditary nonpolyposis colorectal cancer. Mutational analysis was done for MLH1, MSH2, and MSH6 using denaturing high-performance liquid chromatography and sequencing of a blood sample from the daughter. A novel homozygous single base insertion mutation was identified (3634insT) resulting in a premature stop at codon 1,223 in exon 7 of the MSH6 gene. Both parents were found to be heterozygous for the 3634insT mutation. Microsatellite instability testing showed instability in the glioblastoma sample. We report here the first identification of a homozygous mutation in MSH6 in a family with childhood-onset brain tumor, lymphoma, colorectal cancer, and neurofibromatosis type 1 phenotype. Our findings support a role for MSH6 in Turcot syndrome and are consistent with an autosomal recessive mode of inheritance.

An unusual case of Turcot’s syndrome associated with ileal adenocarcinoma, intestinal non-Hodgkin’s lymphoma, and duodenal adenocarcinoma. Review of the classification and genetic basis of Turcot’s syndrome

A 38-year-old man with a history of colonic and small bowel polyposis and glioblastoma was investigated for dyspepsia. Upper GI endoscopy identified an abnormal area in the duodenum, confirmed by histology as high grade non-Hodgkin's B cell MALT lymphoma. Although cases of Turcot's syndrome (TS) (colonic polyposis and primary brain tumour occurring in the same patient) have been previously described, association with haematological malignancy is rare. This is the first report of intestinal lymphoma occurring in an adult with TS.

Familial adenomatous polyposis and benign intracranial tumors: a new variant of Gardner's syndrome

INTRODUCTION

Familial adenomatous polyposis (FAP) is associated with malignant tumors of the central nervous system, predominantly medulloblastomas and glioblastoma multiforme (Turcot's syndrome) and with craniofacial osteomas (Gardner's syndrome). This report details the occurrence of benign, intracranial tumors in two related individuals with Gardner's syndrome, an association not previously described.

PATIENTS AND METHODS

A 57-year-old woman (the propositus), her sister, two of her nieces and one of her grandnephews were previously diagnosed with Gardner's syndrome. The propositus came to neurosurgical attention because of vertigo associated with what proved to be an epidermoid cyst of the cerebellopontine angle. Her unaffected children and her relatives with Gardner's syndrome were examined and underwent computed tomography or magnetic resonance imaging.

RESULTS

A 39-year-old woman with Gardner's syndrome, the niece of the propositus, was found to harbor an asymptomatic left frontal meningioma.

DISCUSSION

Familial adenomatous polyposis, Gardner's syndrome, and that variant of Turcot's syndrome in which medulloblastoma predominate, are associated with a mutation of the adenomatous polyposis coli gene. The demonstration that patients with Gardner's syndrome can also have benign, nonneuroglial, intracranial tumors adds to the previously known extracolonic lesions associated with FAP. The molecular characterization of our patients should reveal if benign intracranial tumors represent a pleiotropic manifestation of the adenomatous polyposis coli gene mutation or if other genes are implicated.

Turcot syndrome with colonic obstruction and small intestinal invagination: report of a case

We report herein the case of a 16-year-old boy diagnosed as having Turcot syndrome, otherwise known as glioma-polyposis syndrome. The patient was transferred from the Department of Neurosurgery where he was undergoing investigation of a brain tumor, to the Department of Medicine for investigation of gastrointestinal symptoms. The patient was diagnosed as having Turcot syndrome, and was then transferred to the Department of Surgery for treatment of an obstruction in the sigmoid colon and small intestinal invagination. A subtotal colectomy with side-to-end ileoproctostomy and release of the invaginations was carried out. Multiple polyps were found in the colon, two of which, including a large polyp that obstructed the colonic lumen, were confirmed histologically to be adenocarcinoma. The remaining polyps were adenomas. A biopsy of the brain tumor confirmed a diagnosis of astrocytoma (WHO grade II). This case report describes the characteristic features of Turcot syndrome presented by this patient.

Genetic alterations in a patient with Turcot's syndrome

Turcot's syndrome (TS) is a rare disorder associated with the development of both brain and colon neoplasms. Because of the very low incidence of the disease, its molecular basis remains unclear. Presented is a TS case of a 30-year-old Japanese male with a histopathologically confirmed diagnosis of both brain tumor (glioblastoma multiforme) and colon tumor (well-differentiated adenocarcinoma). Germline mutations of the p53 gene, somatic mutations of the Ki-ras, p53 and APC genes, and microsatellite instability (MSI) was examined using polymerase chain reaction (PCR)-single strand conformation polymorphism analysis, followed by PCR-direct sequencing, and sequencing after subcloning. No germline mutations of the p53 gene were found. Somatic mutations of Ki-ras and APC genes were found in the colon adenocarcinoma but not in the brain tumor. No somatic mutation of the p53 gene was present in either colon or brain tumors. Microsatellite instability of both colon and brain tumors was positive in two of four loci. These results indicate that the colon tumor of the TS patient carries the Ki-ras and APC gene mutations. The finding of MSI in both the brain and the colon tumors may support the hypothesis that alterations of DNA repair genes are involved in the tumor development of the TS patient.

Polyposis coli, craniofacial exostosis and astrocytoma: the concomitant occurrence of the Gardner's and Turcot syndromes

BACKGROUND

Up to 60% of the patients with known adenomatous polyposis coli may present hyperostosis of the skull and facial bones, and/or a susceptibility to fibromas. This is known as the Gardner's syndrome, and is considered as an allelic variant of familial adenomatous polyposis (FAP). Also, although very rare, an adenomatous polyposis coli may occur with malignant tumors of the central nervous system, known as Turcot syndrome. If both syndromes are different phenotypic presentation of FAP, this would explain a simultaneous occurrence.

METHOD

We report the history of a patient who showed clinical signs of the simultaneous occurrence of both Gardner's and Turcot syndromes. The syndromes are compared, and in view of the literature, a genetic explanation for the concomitant occurrence is discussed.

RESULTS

Evidence obtained from the literature to consider Turcot syndrome as a phenotype of FAB is as follows: (1) The occurrence of Gardner's and Turcot syndromes in one family, but in different members; (2) The presence of congenital hypertrophic retinal pigmented epithelium (CHRPE), which correlates with the expression of polyps in FAP patients, in both syndromes; (3) Linkage of the Turcot phenotype to the adenomatous polyposis coli locus by genetic markers. Evidence obtained from this case report indicates that there is a manifestation of both syndromes in one patient together with a positive family history for FAP.

CONCLUSION

This concomitant occurrence of both Gardner's and Turcot syndromes in one patient clinically supports genetic and ophthalmic investigation to consider Turcot syndrome (like Gardner's syndrome) as a phenotypic variant of FAP. Patients with FAP should be examined for the presence of Gardner's syndrome. In case a Gardner's syndrome is suspected, a computed tomography scan of the brain is recommended because of the possible existence of a simultaneous Turcot syndrome.

Turcot's syndrome: case report and review of the classification

We report a case of association of a brain tumor with multiple colorectal polyposis and offer an analysis of the relevant literature with a view to revising the classification of the syndrome in relation to familial multiple polyposis and Gardner's syndrome. Differences emerged, depending on the brain tumor type, which suggests that this association may be classified as two distinct syndromes.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant condition resulting in the development of more than 100 adenomatous polyps in the large bowel. In addition, a number of extracolonic manifestations of the condition may occur. Recently, increasing knowledge relating to the extracolonic abnormalities, and localization and sequencing of the gene for FAP, have had important implications for screening and long-term follow-up of those affected. In this review the natural history of the disease and the extracolonic manifestations associated with it are considered. Surgical management and advances in understanding at a molecular level are discussed, as well as the problems relating to screening for FAP and the implications of the new knowledge.

Germ-line and somatic mutations of the APC gene in patients with Turcot syndrome and analysis of APC mutations in brain tumors

The Turcot syndrome (TS) is a rare, probably autosomal recessive, disorder characterized by development of primary neuroepithelial tumors of the central nervous system (CNS) and numerous adenomatous colorectal polyps. To examine the possible involvement of mutations of the APC gene, which is responsible for familial adenomatous polyposis (FAP), in Turcot syndrome, we examined DNAs from TS patients for alterations in this gene by means of ribonuclease protection analysis. Germ-line APC mutations were detected in each of three unrelated cases of TS, and additional (somatic) mutations were observed in colonic adenomas that had developed in one of these patients. However, no somatic mutations in APC were found among 91 neuroepithelial tumors (medulloblastoma, glioblastoma, astrocytoma, and oligodendroglioma), whether sporadic or associated with TS. These results suggest that the APC gene is associated with pathogenesis of one feature of TS, but that at least one other gene is responsible for the genesis of neuroepithelial tumors in the CNS.

Turcot's syndrome and familial adenomatous polyposis associated with brain tumor: review of related literature

We investigated clinical manifestations in 124 patients with a possible Turcot's syndrome whose data were taken from documented cases. The cases were subclassified mainly on the bases of the type of familial occurrence and listed in five Tables. We searched for differences in colonic manifestation, histologic type of glioma, mode of inheritance, frequency of parental consanguinity, skin lesions and other accompanying lesions among these five groups. The differences of these clinical findings suggested that glioma-polyposis syndrome should be classified as follows; (1) cases of Turcot's syndrome who had characteristic colonic and brain manifestations, (2) cases of FAP associated with glioma, (3) suspicious cases of glioma-polyposis, and (4) cases other than glioma-polyposis syndrome.

Genetic evidence that Turcot syndrome is not allelic to familial adenomatous polyposis

Turcot syndrome (TS) is a rare genetic disease in which brain tumors occur in association with colonic polyposis. Since Turcot's original description in 1959, there have been disagreements about the mode of inheritance as well as the clinical expression of this condition. Some investigators maintain that TS is a phenotypic variant of the autosomal dominant familial adenomatous polyposis (FAP), while others observe that there are clinical differences between TS and FAP, and that the pattern of inheritance of TS is autosomal recessive. The distribution of persons with colonic lesions in a family with a patient of colonic polyposis and a brain tumor, described in this report, favored the recessive hypothesis. In this family, the involvement of the FAP gene on chromosome 5q21-q22 could be excluded by a linkage study using a panel of FAP-linked DNA markers. This finding, which indicates the occurrence of another polyposis gene elsewhere in the genome, will have consequences for the presymptomatic diagnosis of FAP by linked DNA markers. We conclude that TS is a distinct clinical-genetical entity with the triad of atypical polyposis coli, CNS tumors, and a recessive mode of inheritance.

Turcot's syndrome

A non-familial case of cerebellar medulloblastoma associated with adenomatous polyposis coli is described and the literature is reviewed. This is the second reported case of Turcot's syndrome in Australia. A greater understanding of the genetic implications of this rare condition might be achieved through reporting of cases and long-term documentation with polyposis registries.

Turcot's syndrome: a diagnostic consideration in a child with primary adenocarcinoma of the colon

We report the diagnosis of an adenocarcinoma of the colon in a 12-year-old girl in association with the presence of a small number of adenomatous polyps and a positive family history of a sibling with a central nervous system glioma. These findings implicate Turcot's syndrome as the cause for the development of intestinal and intracranial neoplasms in the two siblings. Since primary adenocarcinoma of the bowel is unusual in children, an underlying predisposing condition should be sought in affected cases.

Familial colorectal cancer and familial adenomatous polyposis

Familial adenomatous polyposis (FAP) affects around 1 in 10,000 individuals; the gene for this condition was recently shown to be located on chromosome 5, and it is only a matter of time before its precise location and function are determined, making prephenotypic, and even prenatal, diagnosis more generally available and reliable. In the mean time, care of FAP families will continue to depend on careful registration of family information, prophylactic bowel surgery and surveillance for other potentially serious manifestations of the disease. Upper gastrointestinal malignancies and desmoid tumours have overtaken colorectal cancer as the leading causes of death in some centres. Other dominantly-inherited colorectal cancer syndromes produce less striking phenotypes, but affect far more individuals than FAP. It appears that there are two patterns of hereditary non-polyposis colorectal cancer (HNPCC) syndromes, one involving cases of bowel cancer alone, the other associated with breast and gynaecological cancers; these may prove to be variable expressions of a common gene abnormality. More effort is required by clinicians managing cases of colorectal cancer to identify affected families in order to offer surveillance and appropriate treatment in the hope that such measures may prevent cancer in family members.

The possible presence of a separate disease entity in nonfamilial polyposis of the large intestine

Familial adenomatosis coli (FAC) traditionally has been diagnosed as the presence of more than 100 colonic adenomas, even if no familial occurrence is present. In the present communication, clinical features of FAC have been compared in detail to detect differences between familial and nonfamilial cases with regard to colonic and extracolonic lesions and to discover whether they constitute the same disease entities. No significant difference was found in the incidence of extracolonic lesions. The average number of colonic polyps in the nonfamilial cases of patients over 30 years old was 1128, the number of polyps was significantly higher in the familial cases (3154). When three patients with approximately 100 polyps were excluded, the mean number of colonic polyps in nonfamilial cases became 2608. This was similar to that of familial cases. Furthermore, the occurrence of approximately 100 polyps was extremely rare in familial patients who were over 30 years old. Therefore, most of the nonfamilial cases can be considered to be familial probands of FAC, but some, such as the three cases in the present study, may be a different disease entity, such as recessive adenomatous polyposis or multiple colonic adenomas.

Turcot's syndrome. A review

Turcot's syndrome represents the association between familial multiple polyposis coli and neural tumors. The syndrome is reviewed with reference to genetics, colonic and central nervous system manifestations. This evidence suggests that Turcot's syndrome represents one manifestation of the pleiotropic autosomal dominant gene responsible for familial polyposis coli and the associated extracolonic manifestations of Gardner's syndrome. A diagnosis of Turcot's syndrome should be restricted to those patients with familial polyposis coli associated with gliomas or medulloblastomas. A further case is presented that is believed to be the first report of such a case in the United Kingdom.

Turcot syndrome. Autosomal dominant or recessive transmission?

The authors analyzed a family in which three descendants presented with adenocarcinoma of the colon. In two of them the presence of colonic adenomatosis was observed. Another family member, a 13-year-old girl, presented with Turcot syndrome, that is, brain tumor associated with colonic adenomatosis. The nature of the hereditary transmission of Turcot syndrome is hence analyzed, discussing whether it happens through an autosomal recessive or a dominant gene. Undoubtedly the family has colonic adenomatosis, a disease considered of autosomal dominant transmission. Based on the clinical observation, the authors suggest that Turcot syndrome may be determined by an autosomal gene with a pleiotropic effect and variable expressivity.