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This guideline presents recommendations for the management of patients with hereditary gastrointestinal cancer syndromes. The initial assessment is the collection of a family history of cancers and premalignant gastrointestinal conditions and should provide enough information to develop a preliminary determination of the risk of a familial predisposition to cancer. Age at diagnosis and lineage (maternal and/or paternal) should be documented for all diagnoses, especially in first- and second-degree relatives. When indicated, genetic testing for a germline mutation should be done on the most informative candidate(s) identified through the family history evaluation and/or tumor analysis to confirm a diagnosis and allow for predictive testing of at-risk relatives. Genetic testing should be conducted in the context of pre- and post-test genetic counseling to ensure the patient's informed decision making. Patients who meet clinical criteria for a syndrome as well as those with identified pathogenic germline mutations should receive appropriate surveillance measures in order to minimize their overall risk of developing syndrome-specific cancers. This guideline specifically discusses genetic testing and management of Lynch syndrome, familial adenomatous polyposis (FAP), attenuated familial adenomatous polyposis (AFAP), MUTYH-associated polyposis (MAP), Peutz-Jeghers syndrome, juvenile polyposis syndrome, Cowden syndrome, serrated (hyperplastic) polyposis syndrome, hereditary pancreatic cancer, and hereditary gastric cancer.

The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as autism spectrum disorder. Germline and somatic mosaic mutations in genes encoding components of the PI3K/AKT/mTOR pathway downstream of PTEN predispose to syndromes with partially overlapping clinical features, termed the \"PTEN-opathies.\" Experimental models of PTEN pathway disruption uncover the molecular and cellular processes influencing clinical phenotypic manifestations. Such insights not only teach us about biological mechanisms in states of health and disease, but also enable more accurate gene-informed cancer risk assessment, medical management, and targeted therapeutics. Hence, the PTEN-opathies serve as a prototype for bedside to bench, and back to the bedside, practice of evidence-based precision medicine.

PTEN hamartoma tumour syndrome is a diverse multi-system disorder predisposing to the development of hamartomatous growths, increasing risk of breast, thyroid, renal cancer, and possibly increasing risk of endometrial cancer, colorectal cancer and melanoma. There is no international consensus on cancer surveillance in PHTS and all current guidelines are based on expert opinion. A comprehensive literature review was undertaken and guidelines were developed by clinicians with expertise from clinical genetics, gynaecology, endocrinology, dermatology, radiology, gastroenterology and general surgery, together with affected individuals and their representatives. Recommendations were put forward for surveillance for breast, thyroid and renal cancers. Limited recommendations were developed for other sites including endometrial, colon and skin. The proposed cancer surveillance recommendations for PHTS require a coordinated multidisciplinary approach and significant patient commitment. The evidence base for cancer surveillance in this guideline are limited, emphasising the need for prospective evaluation of the effectiveness of surveillance in the PHTS population.

Background PTEN hamartoma tumour syndrome (PHTS) encompasses several clinical syndromes with germline mutations in the PTEN tumour suppressor gene, including Cowden syndrome which is characterised by an increased risk of breast and thyroid cancers. Because PHTS is rare, data regarding cancer risks and genotype–phenotype correlations are limited. The objective of this study was to better define cancer risks in this syndrome with respect to the type and location of PTEN mutations. Methods 154 PHTS individuals with a deleterious germline PTEN mutation were recruited from the activity of the Institut Bergonié genetic laboratory. Detailed phenotypic information was obtained for 146 of them. Age and sex adjusted standardised incidence ratio (SIR) calculations, cumulative cancer risk estimations, and genotype–phenotype analyses were performed. Results Elevated SIRs were found mainly for female breast cancer (39.1, 95% CI 24.8 to 58.6), thyroid cancer in women (43.2, 95% CI 19.7 to 82.1) and in men (199.5, 95% CI 106.39 to 342.03), melanoma in women (28.3, 95% CI 7.6 to 35.4) and in men (39.4, 95% CI 10.6 to 100.9), and endometrial cancer (48.7, 95% CI 9.8 to 142.3). Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer. The risk of cancer was two times greater in women with PHTS than in men with PHTS (p<0.05). Conclusions This study shows a considerably high cumulative risk of cancer for patients with PHTS, mainly in women without clear genotype–phenotype correlation for this cancer risk. New recommendations for the management of PHTS patients are proposed.

PTEN Hamartoma Tumor syndrome (PHTS) encompasses a clinical spectrum of heritable disorders including Cowden syndrome (CS), Bannayan–Riley–Ruvalcaba syndrome, and Proteus and Proteus-like syndrome that are associated with germline mutations in the PTEN tumor suppressor gene. Breast cancer risk estimates (67–85 %) for women with germline PTEN mutations are similar to those quoted for patients with germline mutations in the BRCA1/2 genes. With PTEN on several germline gene testing panels, finding PTEN mutations and variants have increased exponentially. PHTS can be differentiated from other hereditary cancer syndromes including Hereditary Breast Ovarian Cancer syndrome, Lynch syndrome, and hamartomatous polyposis syndromes based on personal as well as family history. However, many of the benign features of CS are common in the general population, making the diagnosis of CS challenging. Breast cancer patients with an identified germline PTEN mutation are at increased risk of endometrial, thyroid, renal, and colorectal cancers as well as a second breast cancer. Increased screening for the various component cancers as well as predictive testing in first-degree relatives is recommended. Prophylactic mastectomy may be considered especially if breast tissue is dense or if repeated breast biopsies have been necessary. Management of women with breast cancer suspected of CS who test negative for germline PTEN mutations should be managed as per a mutation carrier if she meets CS diagnostic criteria, and should be offered enrollment in research to identify other predisposition genes.

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden’s syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome–hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden’s syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This US Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management.

ObjectiveIt is recognised that 5% – 10 % of children with macrocephaly and autism spectrum disorder (ASD) and/or intellectual disability (ID) have a heterozygous pathogenic mutation in the PTEN tumour suppressor gene that is associated with PTEN hamartoma tumour syndrome. However, the clinical features and course in children with a pathogenic PTEN mutation are unclear and have not been well documented.Study objectivesWe undertook a retrospective chart review of children (< 18  years) with pathogenic PTEN mutations to ascertain clinical findings, clinical course and possible outcomes.ResultsClinical and molecular data were collected and analysed for 47 patients with PTEN mutation from 38 eligible families. Macrocephaly (average head circumference of + 5.7  SD) with developmental delay, ID and/or ASD were the most common presenting signs/symptoms (66 %). Clinical features included dermatological findings (66 %), gastrointestinal (GI) symptoms (34 %), ASD diagnosis (50 %), abnormal brain imaging (53 % of those examined) and abnormal thyroid imaging (26 %).ConclusionsThis is the largest survey of clinical features in children with PTEN pathogenic mutations to date. It confirms earlier reports of increased rates of neurodevelopmental disorders. Dermatological, GI and thyroid abnormalities are age dependent and may not be present at the time of diagnosis, requiring regular monitoring and medical surveillance. Early paediatric diagnosis is important for institution of medical and developmental surveillance as well as for testing other at- risk family members.

BackgroundCowden syndrome (CS) is associated with benign hamartomatous lesions and risks for thyroid, breast and endometrial cancers. Bannayan–Riley–Ruvalcaba syndrome is an allelic disorder characterised by macrocephaly, intestinal polyps, lipomas, and pigmented penile macules. Diagnostic criteria for CS are based on the presence of a range of clinical features. However, prior data on the component clinical features have been based primarily on compilations of cases reported before development of consensus diagnostic criteria.ObjectiveThis study sought to determine the clinical features most predictive of a mutation in the largest single cohort of patients with clinical testing for PTEN mutations reported to date.MethodsMolecular and clinical data were reviewed on 802 patients referred for PTEN analysis by a single laboratory.ResultsDeleterious mutations were found in 172 (21.4%) subjects. Among mutation carriers significant differences from previous reports were found for the frequencies of several clinical features, including macrocephaly, uterine fibroids, benign breast disease, and endometrial cancer. Logistic regression analyses indicated that female mutation carriers were best identified by the presence of macrocephaly, endometrial cancer, trichilemmomas, papillomatous papules, breast cancer, benign thyroid disease, and benign gastrointestinal (GI) lesions. For males, the most discriminating features were macrocephaly, lipomas, papillomatous papules, penile freckling, benign GI lesions, and benign thyroid disease. Age related differences were also identified.ConclusionThe mutation frequency in patients meeting CS diagnostic criteria (34%) was significantly lower than previously reported, suggesting a need for reevaluation of these criteria. A mutation prediction model has been developed which can help identify patients appropriate for PTEN testing in clinical practice.

PTEN defects underlie disorders with several heritable neoplasms, including the Cowden syndrome, but many patients with these syndromes do not carry PTEN mutations. Some patients with hamartomatous inherited tumors have enhanced function of the WWP1 ubiquitin ligase that increases PTEN degradation and fosters tumor-promoting PI3K activity.