Attenuated familial adenomatous polyposis and Muir-Torre syndrome linked to compound biallelic constitutional MYH gene mutations

Phenotype correlations with pathogenic DNA variants in the MUTYH gene

MUTYH -associated polyposis (MAP) is an autosomal recessive disorder where the inheritance of constitutional biallelic pathogenic MUTYH variants predisposes a person to the development of adenomas and colorectal cancer (CRC). It is also associated with extracolonic and extraintestinal manifestations that may overlap with the phenotype of familial adenomatous polyposis (FAP). Currently, there are discrepancies in the literature regarding whether certain phenotypes are truly associated with MAP. This narrative review aims to explore the phenotypic spectrum of MAP to better characterise the MAP phenotype. A literature search was conducted to identify articles reporting on MAP-specific phenotypes. Clinical data from 2109 MAP patients identified from the literature showed that 1123 patients (53.2%) had CRC. Some patients with CRC had no associated adenomas, suggesting that adenomas are not an obligatory component of MAP. Carriers of the two missense founder variants, and possibly truncating variants, had an increased cancer risk when compared to those who carry other pathogenic variants. It has been suggested that somatic G:C>T:A transversions are a mutational signature of MAP, and could be used as a biomarker in screening and identifying patients with atypical MAP, or in associating certain phenotypes with MAP. The extracolonic and extraintestinal manifestations that have been associated with MAP include duodenal adenomas, duodenal cancer, fundic gland polyps, gastric cancer, ovarian cancer, bladder cancer and skin cancer. The association of breast cancer and endometrial cancer with MAP remains disputed. Desmoids and Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPEs) are rarely reported in MAP, but have long been seen in FAP patients, and thus could act as a distinguishing feature between the two. This collection of MAP phenotypes will assist in the assessment of pathogenic MUTYH variants using the American College of Medical Genetics and the Association for Molecular Pathology (ACMG/AMP) Variant Interpretation Guidelines, and ultimately improve patient care.

Uncommon variants detected via hereditary cancer panel and suggestions for genetic counseling

OBJECTIVE

Hereditary cancer syndromes constitute 5-10% of all cancers. The development of next-generation sequencing technologies has made it possible to examine many hereditary cancer syndrome-causing genes in a single panel. This study's goal was to describe the prevalence and the variant spectrum using NGS in individuals who were thought to have a hereditary predisposition for cancer.

MATERIAL AND METHOD

Analysis was performed for 1254 who were thought to have a familial predisposition for cancer. We excluded 46 patients who were carrying BRCA1/2 variants in this study, for focusing on the rare gene mutations. Sequencing was performed using the Sophia Hereditary Cancer Solution v1.1 Panel and the Qiagen Large Hereditary Cancer Panel. The Illumina MiSeq system was used for the sequencing procedure. The software used for the data analyses was Sophia DDM and QIAGEN Clinical Insight (QCITM) Analyze. The resulting genomic changes were classified according to the current guidelines of ACMG/AMP.

RESULTS

Pathogenic/likely pathogenic variants were detected in 172 (13.7%) of 1254 patients. After excluding the 46 BRCA1/2-positive patients, among the remaining 126 patients; there were 60 (4.8%) breast cancer, 33 (2.6%) colorectal cancer, 9 (0.7%) ovarian cancer, 5 (0.4%) endometrium cancer, 5 (0.4%) stomach cancer, 3 (0.2%) prostate cancer patients. The most altered genes were MUTYH in 27 (2.1%) patients, MMR genes (MLH1, MSH6, MSH, MSH2, PMS2 and EPCAM) in 26 (2%) patients, and ATM in 25 (2%) patients. We also examined the genotype-phenotype correlation in rare variants. Additionally, we identified 11 novel variations.

CONCLUSION

This study provided significant information regarding rare variants observed in the Turkish population because it was carried out with a large patient group. Personalized treatment options and genetic counseling for the patients are therefore made facilitated.

Molecular pathology of skin adnexal tumours

AIMS

Tumours of the cutaneous adnexa arise from, or differentiate towards, structures in normal skin such as hair follicles, sweat ducts/glands, sebaceous glands or a combination of these elements. This class of neoplasms includes benign tumours and highly aggressive carcinomas. Adnexal tumours often present as solitary sporadic lesions, but can herald the presence of an inherited tumour syndrome such as Muir-Torre syndrome, Cowden syndrome or CYLD cutaneous syndrome. In contrast to squamous cell carcinoma and basal cell carcinoma, molecular changes in adnexal neoplasia have been poorly characterised and there are few published reviews on the current state of knowledge.

METHODS AND RESULTS

We reviewed findings in peer-reviewed literature on molecular investigations of cutaneous adnexal tumours published to June 2021.

CONCLUSIONS

Recent discoveries have revealed diverse oncogenic drivers and tumour suppressor alterations in this class of tumours, implicating pathways including Ras/MAPK, PI3K, YAP/TAZ, beta-catenin and nuclear factor kappa B (NF-κB). These observations have identified novel markers, such as NUT for poroma and porocarcinoma and PLAG1 for mixed tumours. Here, we provide a comprehensive overview and update of the molecular findings associated with adnexal tumours of the skin.

Muir-Torre syndrome: a case of unusual coexisting genetic mutations

Muir-Torre syndrome (MTS) is a rare autosomal dominant geno-dermatosis that was independently described by Muir in 1967 and Torre in 1968. MTS is a phenotypic subtype of Lynch syndrome and most commonly arises due to germline mutations in mismatch repair genes. MTS manifests with at least one cutaneous neoplasm and one visceral malignancy.

Forty-eight-year-old female MUTYH carrier presenting with five concurrent primary cancers

Background

MUTYH‐associated polyposis is a rare disorder resulting from mutations involved in DNA mismatch repair. This results in an increased susceptibility to colonic adenomatosis and other cancers. Studies have examined the resulting frequency of extracolonic manifestations; however, these typically occur alone, concurrently, or temporally separate from an already diagnosed colorectal cancer in individuals with a biallelic mutation.

Case

Reported here is a case of five distinct primary neoplasms presenting simultaneously in a patient monoallelic for an MYH mutation. These neoplasms included squamous cell carcinoma of the vulva, rectal adenocarcinoma, synchronous anal adenocarcinoma, papillary thyroid carcinoma, and ovarian serous psammocarcinoma. Throughout her course, she underwent multiple surgical procedures, neoadjuvant chemoradiation, with further adjuvant therapy, and treatment ongoing. Due to her unique presentation, she underwent genetic testing that demonstrated she was monoallelic for an MYH mutation.

Conclusion

The patient had a positive response to her treatment and surgical procedures with ongoing adjuvant therapy. She will continue to undergo further genetic testing, and testing for her children is being considered. This case demonstrates a unique presentation associated with a monoallelic MYH mutation that is not described in the current literature and warrants further investigation.

Case Report: A Frameshift Mutation in MSH2 Exon 2 in a Kidney Recipient With Muir-Torre Syndrome

Muir-Torre syndrome (MTS), a rare subtype of Lynch syndrome, is mostly autosomal dominant, which is caused by germline mutations in DNA mismatch repair (MMR) genes, the resulting microsatellite instability (MSI) of which increases the risk of developing sebaceous and other visceral tumors. Several reports have showed an association between immunosuppressive agents and the progression of latent MTS. In this report, we described a 41-year-old man with a history of kidney transplantation, having a rapid growth of the nodule on the anterior chest under immunosuppressive therapy, which was histologically proved to be sebaceous carcinoma. Systemic evaluation for visceral malignancies revealed sigmoid adenocarcinoma. These findings were consistent with the clinical diagnosis of MTS. Histological findings showed an absence of MMR proteins, including MSH2 and MSH6 both in the sebaceous carcinoma and sigmoid adenocarcinoma on immunohistochemical (IHC) analysis. A frame-shift mutation of c.229_230delAG (p. Ser77fs) in the MSH2 exon 2 in the lesion was detected by next-generation sequencing (NGS) analysis. This case report not only reveals a new site of MSH2 mutation in this family of East Asian descent but also highlights the importance of adequate diagnosis for Muir-Torre syndrome, as well as further prevention of the development of latent visceral tumors in kidney transplant recipients.

Molecular Genetics of Sebaceous Neoplasia

Sebaceous neoplasia primarily includes sebaceous adenoma, sebaceoma, and sebaceous carcinoma (SC). Sebaceous adenoma, sebaceoma, and a subset of cutaneous SC are frequently associated with defective DNA mismatch repair resulting from mutations in MLH1, MSH2, or MSH6. These tumors can be sporadic or associated with Muir-Torre syndrome. SCs without defective DNA mismatch repair have ultraviolet signature mutation or paucimutational patterns. Ocular SCs have low mutation burdens and frequent mutations in ZNF750. Some ocular sebaceous carcinomas have TP53 and RB1 mutations similar to cutaneous SC, whereas others lack such mutations and are associated with human papilloma virus infection.

MLH1 epimutation is a rare mechanism for Lynch syndrome: A case report and review of the literature

Endometrial carcinoma is one of the prototypical malignancies associated with Lynch syndrome, an inherited cancer syndrome most commonly caused by germline mutations in DNA mismatch repair (MMR) genes, although rare alternative mechanisms also exist. In this report, we describe a patient first diagnosed with colorectal cancer at age 33, then vulvar squamous cell carcinoma, facial sebaceous adenoma/sebaceoma, and finally endometrial carcinoma at age 52. All tumors were MLH1/PMS2-deficient by immunohistochemistry, and MLH1 promoter methylation was identified in the endometrial cancer. Germline MLH1 testing was negative for pathogenic variants, but she was subsequently diagnosed with Lynch syndrome secondary to a germline monoallelic constitutional epimutation of the MLH1 promoter. Identification of patients displaying a Lynch syndrome phenotype but lacking germline MMR mutations is important to avoid delays in the diagnosis of Lynch syndrome as well as the initiation of appropriate cancer screening and genetic counseling.

Update on the pathology, genetics and somatic landscape of sebaceous tumours

Cutaneous sebaceous neoplasms show a predilection for the head and neck area of adults and include tumours with benign behaviour, sebaceous adenoma and sebaceoma, and sebaceous carcinoma with potential for an aggressive disease course at the malignant end of the spectrum. The majority of tumours are solitary and sporadic, but a subset of tumours may be associated with Lynch syndrome, also known as hereditary non-polyposis colon cancer (HNPCC) and previously referred to as Muir-Torre syndrome (now known to be part of Lynch syndrome). This review provides an overview of the clinical and histological features of cutaneous sebaceous neoplasia with an emphasis on differentiating features and differential diagnosis. It also offers insights into the recently described molecular pathways involved in the development of sebaceous tumours and their association with Lynch syndrome.

Molecular pathology of Lynch syndrome

Lynch syndrome (LS) is characterised by predisposition to colorectal, endometrial, and other cancers and is caused by inherited pathogenic variants affecting the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2. It is probably the most common predisposition to cancer, having an estimated prevalence of between 1/100 and 1/180. Resources such as the International Society for Gastrointestinal Hereditary Cancer's MMR gene variant database, the Prospective Lynch Syndrome Database (PLSD), and the Colon Cancer Family Register (CCFR), as well as pathological and immunological studies, are enabling advances in the understanding of LS. These include defined criteria by which to interpret gene variants, the function of MMR in the normal control of apoptosis, definition of the risks of the various cancers, and the mechanisms and pathways by which the colorectal and endometrial tumours develop, including the critical role of the immune system. Colorectal cancers in LS can develop along three pathways, including flat intramucosal lesions, which depend on the underlying affected MMR gene. This gives insights into the limitations of colonoscopic surveillance and highlights the need for other forms of anti-cancer prophylaxis in LS. Finally, it shows that the processes of autoimmunisation and immunoediting fundamentally constrain the development of tumours in LS and explain the efficacy of immune checkpoint blockade therapy in MMR-deficient tumours. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Sebaceous lesions of the skin

Sebaceous differentiation is commonly seen in cutaneous neoplasms, both in the context of lesions showing predominantly sebaceous differentiation (e.g., sebaceous adenoma, sebaceoma and sebaceous carcinoma), or as more focal sebaceous components in neoplasms with other primary lines of differentiation. Sebaceous changes can also be a component of benign cystic lesions or epidermal tumours, and sebaceous hyperplasia is commonly encountered. This review is intended to provide an overview of the cutaneous lesions with sebaceous differentiation, with a particular emphasis on facilitating histological diagnosis of neoplasms. In addition, the role of immunohistochemical studies is outlined, as well as the evaluation of potential cases of Muir-Torre syndrome.

Polymorphism and protein expression of MUTYH gene for risk of rheumatoid arthritis

Background

We have previously described the association between rheumatoid arthritis (RA) prevalence and the two mutY Homolog (E. coli) (MUTYH) SNPs (rs3219463 and rs3219476) among the Taiwanese population. This present study will aim to elucidate whether the SNPs can alter the expression of EGFR in the progression of RA.

Methods

The cohort study included 368 Taiwan’s Han Chinese RA patients and 364 healthy controls. Blood samples collected from the participants were analyzed to determine their serum MUTYH levels and to identify rs3219463 SNP of MUTYH from their genomic DNA.

Results

Our data resulted in a statistically significant difference in genotype frequency distributions at rs3219463 for RA patients and controls (p < 0.0002). Also, the patients with G carrier at rs3219463 were less likely to suffer from painful joints (p < 0.006) and DAS28 scores (p < 0.003). Furthermore, the increase in serum level of MUTYH was also observed in RA patients (p < 0.005).

Conclusions

Our study showed that RA is associated with rs3219463 SNP in EGFR gene and an increased serum level of the MUTYH protein. These findings suggest MUTYH is worthy of further investigation as a therapeutic target for RA.

Cutaneous Sebaceous Lesions in a Patient With MUTYH-Associated Polyposis Mimicking Muir-Torre Syndrome

A 76-year-old white male with a history of adenocarcinoma of the rectosigmoideum and multiple colonic polyps removed at the age of 38 and 39 years by an abdominoperitoneal amputation and total colectomy, respectively, presented with multiple whitish and yellowish papules on the face and a verrucous lesion on the trunk. The lesions were surgically removed during the next 3 years and a total of 13 lesions were investigated histologically. The diagnoses included 11 sebaceous adenomas, 1 low-grade sebaceous carcinoma, and 1 squamous cell carcinoma. In some sebaceous lesions, squamous metaplasia, intratumoral heterogeneity, mucinous changes, and peritumoral lymphocytes as sometimes seen in sebaceous lesions in Muir-Torre syndrome were noted. Mutation analysis of the peripheral blood revealed a germline mutation c.692G>A,p.(Arg231His) in exon 9 and c.1145G>A, p.(Gly382Asp) in exon 13 of the MUTYH gene. A KRAS mutation G12C (c.34G>T, p.Gly12Cys) was detected in 1 sebaceous adenoma and a NRAS mutation Q61K (c.181C>A, p.Gln61Lys) was found in 2 other sebaceous adenomas. No germline mutations in MLH1, MSH2, MSH6 and PMS2 genes, no microsatellite instability, no aberrant methylation of MLH1 promoter, and no somatic mutations in MSH2 and MSH6 were found. An identical MUTYH germline mutation was found in the patient's daughter. Despite striking clinicopathological similarities with Muir-Torre syndrome, the molecular biologic testing confirmed the final diagnosis of MUTYH-associated polyposis.

Risk of extracolonic cancers for people with biallelic and monoallelic mutations in MUTYH

Germline mutations in the DNA base excision repair gene MUTYH are known to increase a carrier's risk of colorectal cancer. However, the risks of other (extracolonic) cancers for MUTYH mutation carriers are not well defined. We identified 266 probands (91% Caucasians) with a MUTYH mutation (41 biallelic and 225 monoallelic) from the Colon Cancer Family Registry. Mutation status, sex, age and histories of cancer from their 1,903 first- and 3,255 second-degree relatives were analyzed using modified segregation analysis conditioned on the ascertainment criteria. Compared with incidences for the general population, hazard ratios (HRs) (95% confidence intervals [CIs]) for biallelic MUTYH mutation carriers were: urinary bladder cancer 19 (3.7-97) and ovarian cancer 17 (2.4-115). The HRs (95% CI) for monoallelic MUTYH mutation carriers were: gastric cancer 9.3 (6.7-13); hepatobiliary cancer 4.5 (2.7-7.5); endometrial cancer 2.1 (1.1-3.9) and breast cancer 1.4 (1.0-2.0). There was no evidence for an increased risk of cancers at the other sites examined (brain, pancreas, kidney or prostate). Based on the USA population incidences, the estimated cumulative risks (95% CI) to age 70 years for biallelic mutation carriers were: bladder cancer 25% (5-77%) for males and 8% (2-33%) for females and ovarian cancer 14% (2-65%). The cumulative risks (95% CI) for monoallelic mutation carriers were: gastric cancer 5% (4-7%) for males and 2.3% (1.7-3.3%) for females; hepatobiliary cancer 3% (2-5%) for males and 1.4% (0.8-2.3%) for females; endometrial cancer 3% (2%-6%) and breast cancer 11% (8-16%). These unbiased estimates of both relative and absolute risks of extracolonic cancers for people, mostly Caucasians, with MUTYH mutations will be important for their clinical management.

Muir-Torre syndrome (MTS): An update and approach to diagnosis and management

Muir-Torre syndrome (MTS) is a rare genetic condition that predisposes individuals to skin tumors and visceral malignancies. Because of the potentially aggressive nature of internal malignancies and sebaceous carcinoma, and the tendency to have multiple low-grade visceral cancers, close cancer surveillance is required in individuals and their families with this usually autosomal dominant disorder. Although the majority of MTS is caused by mutations in DNA mismatch repair genes resulting in microsatellite instability, a newly described subtype of MTS does not demonstrate microsatellite instability and may be inherited in an autosomal recessive pattern. In addition, MTS may be unmasked in transplant recipients taking specific immunosuppressant drugs or other immunosuppressed patients. Neoplasms may be subject to immunohistochemistry or both immunohistochemistry and genetic testing to confirm the diagnosis of MTS. Here, we offer an update and an approach to the diagnosis and management of MTS with a particular emphasis on the role of immunohistochemistry and genetic testing.

JAAD Grand Rounds quiz: A subcutaneous nodule on the right shoulder

LEARNING OBJECTIVES

At the conclusion of this learning activity, physician participants should be able to assess their own diagnostic and patient management skills and use the results of this exercise to help determine personal learning needs. Instructions: In answering each question, refer to the specific directions provided. Because it is often necessary to provide information occurring later in a series that give away answers to earlier questions, please answer the questions in each series in sequence.

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.

Genetic predisposition to colorectal cancer: Where we stand and future perspectives

The development of colorectal cancer (CRC) can be influenced by genetic factors in both familial cases and sporadic cases. Familial CRC has been associated with genetic changes in high-, moderate- and low-penetrance susceptibility genes. However, despite the availability of current gene-identification techniques, the genetic causes of a considerable proportion of hereditary cases remain unknown. Genome-wide association studies of CRC have identified a number of common low-penetrance alleles associated with a slightly increased or decreased risk of CRC. The accumulation of low-risk variants may partly explain the familial risk of CRC, and some of these variants may modify the risk of cancer in patients with mutations in high-penetrance genes. Understanding the predisposition to develop CRC will require investigators to address the following challenges: the identification of genes that cause uncharacterized hereditary cases of CRC such as familial CRC type X and serrated polyposis; the classification of variants of unknown significance in known CRC-predisposing genes; and the identification of additional cancer risk modifiers that can be used to perform risk assessments for individual mutation carriers. We performed a comprehensive review of the genetically characterized and uncharacterized hereditary CRC syndromes and of low- and moderate-penetrance loci and variants identified through genome-wide association studies and candidate-gene approaches. Current challenges and future perspectives in the field of CRC predisposition are also discussed.

Muir-Torre syndrome: case report and molecular characterization

CONTEXT

Muir-Torre syndrome is a rare autosomal dominant genodermatosis caused by mutations in the mismatch repair genes. It is characterized by the presence of sebaceous skin tumors and internal malignancies, affecting mainly the colon, rectum and urogenital tract. Awareness of this syndrome among physicians can lead to early diagnosis of these malignancies and a better prognosis.

CASE REPORT

We report the case of a Chilean patient who, over the course of several years, had multiple skin lesions, endometrial cancer and colon cancer. The syndrome was diagnosed using molecular techniques such as microsatellite instability analysis, immunohistochemistry and DNA sequencing, which allowed us to find the causative mutation.

CONCLUSION

Molecular diagnostics is a highly useful tool, since it allows clinicians to confirm the presence of mutations causing Muir-Torre syndrome. It is complementary to the analysis of the clinical data, such as dermatological presentation, presence of visceral malignancies and family history of colorectal tumors, and it provides important knowledge to help physicians and patients choose between treatment options.

French experts report on MUTYH-associated polyposis (MAP)

Recent years have been characterised by an improvement in our knowledge of genetic determinism of adenomatous polyposes and by the description in 2002 of a new entity called "MUTYH-associated polyposis" (MAP), related to biallelic mutations of this gene. Its autosomal recessive mode of inheritance contrasts with the autosomal dominant inheritance of the classical "familial adenomatous polyposis" (FAP), associated with an APC germline mutation. Although some phenotypic features may be of value to distinguish these two conditions, their clinical "spectra" largely overlap and the differential diagnosis may be difficult. The purpose of this expertise conducted under the auspices of the French Institut National du Cancer (INCa) was to assess the current state of knowledge on MUTYH-associated polyposis and to establish some recommendations in the field of molecular analysis (indications of tests and analysis strategies for affected patients and their relatives) and of clinical management based on available data in the literature, on the results from the French molecular genetics laboratories performing MUTYH analysis and on the opinions of biologists and clinicians experts (genetic counsellors and gastroenterologists). The risk of colorectal cancer among relatives carrying a monoallelic MUTYH mutation was also studied.

Role of MUTYH in human cancer

MUTYH, a human ortholog of MutY, is a post-replicative DNA glycosylase, highly conserved throughout evolution, involved in the correction of mismatches resulting from a faulty replication of the oxidized base 8-hydroxyguanine (8-oxodG). In particular removal of adenine from A:8-oxodG mispairs by MUTYH activity is followed by error-free base excision repair (BER) events, leading to the formation of C:8-oxodG base pairs. These are the substrate of another BER enzyme, the OGG1 DNA glycosylase, which then removes 8-oxodG from DNA. Thus the combined action of OGG1 and MUTYH prevents oxidative damage-induced mutations, i.e. GC->TA transversions. Germline mutations in MUTYH are associated with a recessively heritable colorectal polyposis, now referred to as MUTYH-associated polyposis (MAP). Here we will review the phenotype(s) associated with MUTYH inactivation from bacteria to mammals, the structure of the MUTYH protein, the molecular mechanisms of its enzymatic activity and the functional characterization of MUTYH variants. The relevance of these results will be discussed to define the role of specific human mutations in colorectal cancer risk together with the possible role of MUTYH inactivation in sporadic cancer.

MUTYH-associated polyposis (MAP), the syndrome implicating base excision repair in inherited predisposition to colorectal tumors

In 2002, Al-Tassan and co-workers described for the first time a recessive form of inherited polyposis associated with germline mutations of MUTYH, a gene encoding a base excision repair (BER) protein that counteracts the DNA damage induced by the oxidative stress. MUTYH-associated polyposis (MAP) is now a well-defined cancer susceptibility syndrome, showing peculiar molecular features that characterize disease progression. However, some aspects of MAP, including diagnostic criteria, genotype-phenotype correlations, pathogenicity of variants, as well as relationships between BER and other DNA repair pathways, are still poorly understood. A deeper knowledge of the MUTYH expression pattern is likely to refine our understanding of the protein role and, finally, to improve guidances for identifying and handling MAP patients.

[Gastrointestinal polyposis syndromes]

Hereditary gastrointestinal polyposis syndromes account for around 1% of all colorectal cancers; most of them are associated with a broad spectrum of extracolonic tumors. The initial diagnosis is based on endoscopic findings and polyp histology. Molecular genetic screening is important for the delineation of conditions with a similar phenotype such as autosomal dominant familial adenomatous polyposis (FAP) and autosomal recessive MUTYH-associated polyposis (MAP). Identification of the germline mutation in an affected person is a prerequisite for the exact evaluation of the recurrence risk in relatives and the predictive testing of asymptomatic persons at risk. Beside cases with attenuated adenomatosis or few colorectal adenomas, diagnostic difficulties are common among the hamartomatous polyposes such as the juvenile polyposis syndrome due to their broad clinical overlap and uncertainties in histological assessment. Several poorly defined nonhereditary polyposis syndromes and those with an as yet unknown etiology exist including hyperplastic polyposis syndrome. Early detection and accurate classification are essential since effective methods for surveillance and treatment are available.

MUTYH Associated Polyposis (MAP)

MUTYH Associated Polyposis (MAP), a Polyposis predisposition caused by biallelic mutations in the Base Excision Repair (BER) gene MUTYH, confers a marked risk of colorectal cancer (CRC). The MAP phenotype is difficult to distinguish from other hereditary CRC syndromes. Especially from Familial Adenomatous Polyposis (FAP) and to a lesser extend Lynch Syndrome, which are caused by germline mutations in the APC and Mismatch Repair (MMR) genes, respectively.

Here we review research findings regarding MUTYH interactions, genotypic and phenotypic characteristics of MAP, as well as surveillance and treatment of the disease. The applied papers, published between 1/1 2002- 1/2 2008, were found through PubMed.

The exact role of MUTYH in CRC tumorgenesis is still uncertain, although MAP tumors show distinct molecular features, including somatic G:C>T:A transversions in the APC gene. Furthermore, cooperation between the BER and the MMR systems exists, as MUTYH interacts with MMR gene-products. Possibly, monoallelic defects in both pathways are of significance to CRC development.

Specific MUTYH variants are found to be characteristic in distinct ethnic populations, which could facilitate future genetic screening. Knowledge concerning functional consequences of many MUTYH germline mutations remains sparse. Most thoroughly investigated are the two most common MUTYH variants, Y179C and G396D, both generating dysfunctional gene products.

Phenotypic features of MAP include: development of 10-100 colorectal adenomas, debuting at 46-47 years, often CRC at time of clinical diagnosis, and in some, development of extracolonic manifestations.

Cancer risks for monoallelic MUTYH mutation carriers with a family history of colorectal cancer

Cancer risks for a person who has inherited a MUTYH mutation from only one parent (monoallelic mutation carrier) are uncertain. Using the Colon Cancer Family Registry and Newfoundland Familial Colon Cancer Registry, we identified 2,179 first- and second-degree relatives of 144 incident colorectal cancer (CRC) cases who were monoallelic or biallelic mutation carriers ascertained by sampling population complete cancer registries in the United States, Canada and Australia. Using Cox regression weighted to adjust for sampling on family history, we estimated that the country-, age- and sex-specific standardized incidence ratios (SIRs) for monoallelic mutation carriers, compared to the general population, were: 2.04 (95% confidence interval, CI 1.56-2.70; p < 0.001) for CRC, 3.24 (95%CI 2.18-4.98; p < 0.001) for gastric cancer, 3.09 (95%CI 1.07-12.25; p = 0.07) for liver cancer and 2.33 (95%CI 1.18-5.08; p = 0.02) for endometrial cancer. Age-specific cumulative risks to age 70 years, estimated using the SIRs and US population incidences, were: for CRC, 6% (95%CI 5-8%) for men and 4% (95%CI 3-6%) for women; for gastric cancer, 2% (95%CI 1-3%) for men and 0.7% (95%CI 0.5-1%) for women; for liver cancer, 1% (95%CI 0.3-3%) for men and 0.3% (95%CI 0.1-1%) for women and for endometrial cancer, 4% (95%CI 2-8%). There was no evidence of increased risks for cancers of the brain, pancreas, kidney, lung, breast or prostate. Monoallelic MUTYH mutation carriers with a family history of CRC, such as those identified from screening multiple-case CRC families, are at increased risk of colorectal, gastric, endometrial and possibly liver cancers.

Papillary thyroid cancer in a patient with MUTYH-associated polyposis (MAP)

We describe a patient with MUTYH-associated polyposis diagnosed with colon cancer at 33 years of age, as well as gastric polyps at a later age. She was also diagnosed with papillary thyroid cancer at age 35. MUTYH-associated polyposis is an autosomal recessively inherited disease which has clinical overlap with Familial adenomatous polyposis and its attenuated form, in that it is associated with risk of colon cancer at a young age. Extra-intestinal cancers have also been reported in patients with MUTYH-associated polyposis; however the tumor spectrum is still evolving. National Comprehensive Cancer Network guidelines recommend screening for colon, duodenal and gastric polyps in individuals with MUTYH-associated polyposis. Screening for extra-intestinal cancers i.e. thyroid cancer is presently not part of these recommendations. These will likely continue to evolve as the MUTYH-associated polyposis tumor spectrum is better understood as a result of future case reports and research.

Germline mutations in cancer susceptibility genes: an overview for nurses

OBJECTIVE

To provide an overview of hereditary cancer susceptibility genes and associated cancer risks.

DATA SOURCES

Peer reviewed published research studies and review articles.

CONCLUSIONS

Identifying deleterious mutations in cancer susceptibility genes allows for clarification of cancer risk in individual family members and risk-level appropriate screening, and risk management recommendations. Evolving knowledge of the role of germline mutations provides an unprecedented opportunity to reduce cancer incidence, morbidity, and morality.

IMPLICATIONS FOR NURSING PRACTICE

To provide individuals/families with accurate cancer risk management information and guidance, oncology nurses must be familiar with scientific discoveries related to cancer susceptibility genes.

MUTYH-associated polyposis (MAP)

The human mutY homologue (MUTYH) gene is responsible for inheritable polyposis and colorectal cancer. This review discusses the molecular genetic aspects of the MUTYH gene and protein, the clinical impact of mono- and biallelic MUTYH mutations and histological aspects of the MUTYH tumors. Furthermore, the relationship between MUTYH and the mismatch repair genes in colorectal cancer (CRC) families is examined. Finally, the role of other base excision repair genes in polyposis and CRC patients is discussed.

Sebaceous neoplasia and the Muir-Torre syndrome: important connections with clinical implications

Sebaceous neoplasia comprises a spectrum ranging from benign to malignant. Proper histological identification is important for treatment, prognosis and potential association with the Muir-Torre syndrome (MTS). Our increased understanding of the significance and pathogenesis of these tumours has led to improved risk stratification, screening recommendations, and treatment of patients with an initial presentation of a sebaceous tumour. This review focuses on the diagnostic and histological features of sebaceous lesions, the MTS, and recent insights into the molecular pathogenesis of sebaceous tumours.

Relative role of APC and MUTYH mutations in the pathogenesis of familial adenomatous polyposis

OBJECTIVE

Familial adenomatous polyposis (FAP) is an interesting model for the study of colorectal tumour. Two genes contribute to the FAP phenotype - APC and MUTYH - but their relative role is still undefined. The objective of this study was to evaluate the contribution of the two genes to the pathogenesis of FAP by means of a series of FAP families.

MATERIAL AND METHODS

Sixty-one unrelated families with a diagnosis of FAP and a total of 187 affected individuals were evaluated. After extracting DNA, APC and MUTYH genes were sequenced.

RESULTS

In the whole series of patients, colectomy with ileorectal anastomosis was the most frequent surgery, although the number of patients treated by total proctocolectomy and ileoanal anastomosis was increasing. Duodenal and jejunal-ileal adenomas were present in more than half of the patients. Constitutional mutations were detected in 37 of the 45 families (82.2%); there were 33 families with APC and 4 with MUTYH alterations. Age at onset of polyposis and age at surgery were 10-15 years delayed for carriers of MUTYH mutations; cancer at diagnosis was frequent, and extracolonic manifestations were diagnosed in the majority of MUTYH-positive families. MUTYH-associated polyposis showed the horizontal transmission expected for recessive inheritance (at variance with the dominant pattern seen with APC mutations).

CONCLUSIONS

At least two genes are associated with the FAP phenotype. APC mutations account for the majority of cases, while MUTYH mutations can be observed in 10% of patients. There are few but definite differences between APC- and MUTYH-associated FAP, such as age at diagnosis and pattern of transmission.

Expanded extracolonic tumor spectrum in MUTYH-associated polyposis

BACKGROUND & AIMS

MUTYH-associated polyposis (MAP) is characterized by a lifetime risk of colorectal cancer of up to 100%. However, no systematic evaluation of extracolonic manifestations has been reported.

METHODS

A large cohort of MAP patients was recruited from a European multicenter study. Data were collected on 276 cases from 181 unrelated families. Information on extracolonic tumor spectrum and incidence were evaluated to determine cumulative lifetime risk, which was compared with that of the general population to obtain standardized incidence ratios (SIRs).

RESULTS

Duodenal polyposis occurred in 17% of cases; the relative risk (SIR) of duodenal cancer was 129 (95% confidence interval [CI]: 16-466), whereas the lifetime risk was 4%. The incidence of extraintestinal malignancies among cases was almost twice that of the general population (SIR: 1.9; 95% CI: 1.4-2.5), with a lifetime risk of 38%. We observed a significant increase in the incidence of ovarian, bladder, and skin cancers (SIR: 5.7, 7.2, and 2.8, respectively) and a trend of increased risk of breast cancer among cases. The median ages of onset of these 4 malignancies ranged from 51 to 61 years. In contrast to familial adenomatous polyposis, no desmoid tumors were observed, but sebaceous gland tumors, characteristic of the Muir-Torre variant of Lynch syndrome, occurred in 5 patients.

CONCLUSIONS

The relative risks for several extraintestinal malignancies increased in patients with MAP, but based on the spectrum of cancers (which overlaps with that of Lynch syndrome) and the relatively advanced age at onset, intensive surveillance measures other than frequent endoscopy are unlikely to be helpful to patients with MAP.

A novel complex mutation in MSH2 contributes to both Muir-Torre and Lynch Syndrome

Mutations in mismatch repair genes lead to Lynch Syndrome, the most common form of inherited colorectal cancer. In this report, we describe a novel complex germline mutation c.[1601_1661+92dup; 1591_1611del] of the mismatch repair gene, MSH2. This mutation, which segregates with the disease phenotype, was discovered in a Lynch syndrome kindred that also shows a history of the Muir-Torre syndrome. Interestingly, several tumors from this family displayed microsatellite instability, a hallmark of Lynch syndrome tumors but no consistent, concomitant loss of MSH2 protein expression. In addition, a subset of tumors showed neither prototypical feature of microsatellite instability nor immunohistochemistry deficiency, highlighting the importance of a detailed molecular analysis of rare genetic alterations. This mutation and the atypical clinical manifestations observed underscore the genetic complexity underlying Lynch syndrome, and the importance of comprehensive molecular screening in the diagnosis and early detection of colorectal and other associated cancers.

Clustering of sebaceous gland carcinoma, papillary thyroid carcinoma and breast cancer in a woman as a new cancer susceptibility disorder: a case report

Introduction

Multiple distinct tumors arising in a single individual or within members of a family raise the suspicion of a genetic susceptibility disorder.

Case presentation

We present the case of a 52-year-old Caucasian woman diagnosed with sebaceous gland carcinoma of the eyelid, followed several years later with subsequent diagnoses of breast cancer and papillary carcinoma of the thyroid. Although the patient was also exposed to radiation from a pipe used in the oil field industry, the constellation of neoplasms in this patient suggests the manifestation of a known hereditary susceptibility cancer syndrome. However, testing for the most likely candidates such as Muir-Torre and Cowden syndrome proved negative.

Conclusion

We propose that our patient's clustering of neoplasms either represents a novel cancer susceptibility disorder, of which sebaceous gland carcinoma is a characteristic feature, or is a variant of the Muir-Torre syndrome.

MUTYH-associated polyposis

MUTYH-associated polyposis (MAP) is an autosomal recessive disorder characterised by adenomatous polyps of the colorectum and a very high risk of colorectal cancer. It appears to be at least as prevalent as autosomal dominant familial adenomatous polyposis (that is caused by truncating mutations in the APC gene) with which it shares important gastroenterological features. It was first recognised as recently as 2002 and its full phenotype and natural history are still being characterised. Key extracolonic manifestations include a predisposition to duodenal adenomas and cancer and a modest increase in risk for several extraintestinal tumours. Testing for mutations in the MUTYH gene is indicated in patients who have multiple colorectal adenomas or a family history suggestive of autosomal recessive colorectal cancer and for the siblings and spouses of patients with MAP in order to inform surveillance and treatment for patients and their families.

Aggressive phenotype of MYH-associated polyposis with jejunal cancer and intra-abdominal desmoid tumor: report of a case

MYH-associated polyposis is an inherited autosomal recessive disease, linked to biallelic germline MYH mutations, which predisposes to the development of multiple colorectal adenomas and cancer. The colonic and extracolonic phenotype of this syndrome is very heterogeneous. We report the case of a young male patient with an aggressive MYH-associated polyposis phenotype. He presented at aged 30 years with more than 100 colonic polyps and 4 colonic adenocarcinomas. At aged 35 years, Spigelman Stage IV duodenal adenomatosis was detected. When he was 39 years old, he developed three synchronous jejunal adenocarcinomas and a mesenteric desmoid tumor. Based on this report, we believe that screening of the entire small bowel should be recommended in MYH-associated polyposis patients, especially in those with duodenal adenomas. Similar to patients with familial adenomatous polyposis, desmoid tumors also may be part of the clinical spectrum of MYH-associated polyposis and may prove to be a significant clinical problem in patients submitted to prophylactic colectomy.

Hereditary colorectal cancer: MYH-associated polyposis and other newly identified disorders

Historically, discussions of familial adenomatous polyposis and hereditary non-polyposis colon cancer have dominated lectures and writings on hereditary predisposition to colorectal cancer. In the last decade, the subject has grown well beyond the two entities. In this paper, five topics relevant to genetic risk assessment for colorectal cancer are reviewed. These include the autosomal recessive MYH-associated polyposis, hyperplastic polyposis and serrated pathway syndrome, the association of autosomal dominant juvenile polyposis with hereditary hemorrhagic telangiectasia, familial colorectal cancer type X, and the syndrome of biallelic DNA mismatch repair gene mutations. Knowledge of these entities may assist clinicians to recognize and manage cases that do not fit into the more common syndromes of colorectal cancer predisposition.

Endometrial cancer and somatic G>T KRAS transversion in patients with constitutional MUTYH biallelic mutations

MUTYH-associated polyposis (MAP) is an autosomal recessive condition predisposing to colorectal cancer, caused by constitutional biallelic mutations in the base excision repair (BER) gene MUTYH. Colorectal tumours from MAP patients display an excess of somatic G>T mutations in the APC and KRAS genes due to defective BER function. To date, few extracolonic manifestations have been observed in MAP patients, and the clinical spectrum of this condition is not yet fully established. Recently, one patient with a diagnosis of endometrial cancer and biallelic MUTYH mutations has been described. We here report on two additional unrelated MAP patients with biallelic MUTYH germline mutations who developed endometrioid endometrial carcinoma. The endometrial tumours were evaluated for PTEN, PIK3CA, KRAS, BRAF and CTNNB1 mutations. A G>T transversion at codon 12 of the KRAS gene was observed in one tumour. A single 1bp frameshift deletion of PTEN was observed in the same sample. Overall, these findings suggest that endometrial carcinoma is a phenotypic manifestations of MAP and that inefficient repair of oxidative damage can be involved in its pathogenesis.

Proposal of new gene filtering method, BagPART, for gene expression analysis with small sample

A significant problem in gene expression analysis is that the sample size is substantially lower than the number of genes. Bagging is an effective method of solving this problem in the case of small sample datasets. We have devised a combination method, called the BagPART filtering method, that uses the projective adaptive resonance theory (PART) to select important genes and achieve a binary classification more accurately (p<10(-10)) than conventional methods, particularly when the sample size is small.

Germline mutation prevalence in the base excision repair gene, MYH, in patients with endometrial cancer

Germline mutations in the base excision repair gene, MutY human homolog (MYH), have recently been associated with a recessively inherited multiple adenoma polyposis syndrome and colorectal cancer. The spectrum of extracolonic lesions is still being characterized, although preliminary reports suggest that bi-allelic mutation carriers may share some of the clinical features of other hereditary colon cancer syndromes. Of 225 endometrial cancer patients, we identified one individual as a compound heterozygote, carrying mutations Y165C and G382D of MYH, and five individuals with heterozygous defects (three G382D and two Y165C). The patient with the bi-allelic Y165C/G382D mutation also had a sebaceous carcinoma, a feature of Muir-Torre syndrome. Although several intronic polymorphisms were detected in the heterozygous carriers, no other pathogenic variants were identified. While not conclusive, this novel and interesting finding provides evidence that bi-allelic germline mutations in MYH may increase susceptibility to endometrial cancer.

Sebaceous adenomas in an MYH associated polyposis patient of Indian (Gujarati) origin

MYH associated polyposis is an autosomal recessive polyposis syndrome with a high risk of large bowel cancer, caused by mutations in the DNA repair gene MYH. Founder mutations have been described in different ethnic groups. Muir Torre Syndrome is the association of internal malignancies with sebaceous gland tumours; Lynch Syndrome/Hereditary Non Polyposis Cancer is the best known cause. There has been a previous report of sebaceous gland tumours in an Italian patient with MYH associated polyposis. We describe a man of Indian (Gujarati) descent who has MYH associated polyposis and multiple sebaceous adenomas of the skin.

BRAF Mutations in Multiple Sebaceous Hyperplasias of Patients Belonging to MYH-Associated Polyposis Pedigrees

The characteristics of sebaceous gland hyperplasia (SGH) consist of yellowish or skin-colored papules and nodules. Chronic sun exposure and immunosuppressed conditions are the main environmental risk factors, whereas chronological aging regulated by hormones and molecular changes are the intrinsic risk factors. We have evaluated the contribution of BRAF, K-Ras, and N-Ras mutations to the pathogenesis of SGHs in four patients belonging to three MYH-associated polyposis (MAP) pedigrees. MAP is an autosomal-recessive disease characterized by multiple colorectal adenomas and cancer. Immunohistochemistry of mismatch repair and APC proteins was performed. DNA isolated from blood lymphocytes and formalin-fixed or paraffin-embedded SGHs was PCR amplified and sequenced. In the SGH patients, we detected T1796A heterozygous substitution (V600E) in the BRAF gene. Compound biallelic germline MYH mutations (Y165C/G382D, R168H/379delC, and Y90X/delGGA464) were detected in the MAP patients. In contrast to the majority of melanocytic lesions, activating hotspot mutations in BRAF have not been involved so far in the pathogenesis of SGH. BRAF mutation is not a specific marker of melanocytic cancerogenesis, and it can also be involved in SGHs. In both melanocytic and non-melanocytic skin tumors, BRAF mutation is linked to early tumorigenesis events.