Gene variants associated to malignant thyroid disease in familial adenomatous polyposis: a novel APC germline mutation

De novo familial adenomatous polyposis associated thyroid cancer with a c.2929delG frameshift deletion mutation in APC: a case report and literature review

BACKGROUND

Germline mutations in the APC gene located on chromosome 5q 21-22 can lead to familial adenomatous polyposis (FAP) and the development of colorectal cancer (CRC) if left untreated. As a rare extracolonic manifestation, thyroid cancer is diagnosed in about 2.6% of FAP patients. The genotype-phenotype correlation in FAP patients with thyroid cancer remains unclear.

CASE PRESENTATION

We present a 20-year-old female of FAP with thyroid cancer as the initial manifestation. The patient was asymptomatic and developed colon cancer liver metastases 2 years after the diagnosis of thyroid cancer. The patient underwent multiple surgical treatments in several organs, and regular colonoscopy with endoscopic polypectomy was performed. Genetic testing demonstrated the c.2929delG (p.Gly977Valfs*3) variant in exon 15 of the APC gene. This represents a previously undescribed APC mutation. This mutation causes loss of multiple structures on the APC gene including the 20-amino acid repeats, the EB1 binding domain, and the HDLG binding site, which may be pathogenic through β-catenin accumulation, cell cycle microtubule dysregulation, and tumor suppressor inactivation.

CONCLUSIONS

We report a de novo FAP case with thyroid cancer presenting atypically aggressive features harboring a novel APC mutation and review APC germline mutations in patients with FAP-associated thyroid cancer.

Looking at Thyroid Cancer from the Tumor-Suppressor Genes Point of View

Thyroid cancer is the most frequent endocrine malignancy and accounts for approximately 1% of all diagnosed cancers. A variety of mechanisms are involved in the transformation of a normal tissue into a malignant one. Loss of tumor-suppressor gene (TSG) function is one of these mechanisms. The normal functions of TSGs include cell proliferation and differentiation control, genomic integrity maintenance, DNA damage repair, and signaling pathway regulation. TSGs are generally classified into three subclasses: (i) gatekeepers that encode proteins involved in cell cycle and apoptosis control; (ii) caretakers that produce proteins implicated in the genomic stability maintenance; and (iii) landscapers that, when mutated, create a suitable environment for malignant cell growth. Several possible mechanisms have been implicated in TSG inactivation. Reviewing the various TSG alteration types detected in thyroid cancers may help researchers to better understand the TSG defects implicated in the development/progression of this cancer type and to find potential targets for prognostic, predictive, diagnostic, and therapeutic purposes. Hence, the main purposes of this review article are to describe the various TSG inactivation mechanisms and alterations in human thyroid cancer, and the current therapeutic options for targeting TSGs in thyroid cancer.

Management of pediatric differentiated thyroid cancer: An overview for the pediatric oncologist

Differentiated thyroid cancer (DTC) is the most common childhood thyroid malignancy. The standard of care for pediatric DTC is total thyroidectomy followed by radioactive iodine (RAI) treatment when indicated. Molecular changes and potential therapeutic targets have been recently described in pediatric thyroid cancer. Pediatric oncologists are increasingly involved in the evaluation of thyroid nodules in childhood cancer survivors and in the management of advanced thyroid cancer. In 2015, the American Thyroid Association published management guidelines for children with DTC. We provide an overview of the current standard of care and highlight available targeted therapies for progressive or RAI refractory DTC.

Outcome of thyroid ultrasound screening in FAP patients with a normal baseline exam

Familial adenomatous polyposis (FAP) is a hereditary cancer syndrome associated with a substantial lifetime risk for colorectal cancer. The leading extra-colonic causes of cancer in FAP include duodenal and thyroid cancer (TC). Recent guidelines recommend annual thyroid ultrasound (TUS) screening beginning in the teenage years but the evidence to support the interval particularly in FAP patients with a normal baseline ultrasound is lacking. TUS results from FAP patients enrolled in a thyroid screening program from 2006 to 2016 and who had at least 2 TUS were reviewed. TUS findings were classified as normal, low (LR) or high risk (HR) for TC based on nodule characteristics as determined by American Thyroid Association (ATA) guidelines. We assessed the incidence of TC in patient with normal baseline TUS and factors associated with TC. 264 FAP patients were included. Baseline TUS was normal in 167, LR in 74, and HR in 24 patients. Patients were observed for a mean 4.8 years and underwent an average of 3 TUS. Patients with normal baseline TUS did not develop TC during the course of follow up of 5.1 years. TC developed in 6 patients (2.3%) all with baseline nodules; 5 in the LR group and 1 in the HR group. Factors associated with development of TC were presence of baseline nodule(s) and female sex. The development of TC in FAP patients in a TUS screening program with short term follow up is low and no FAP patient with a normal baseline TUS developed TC during observation. Annual TUS in patients with a normal baseline TUS may not be needed. Extending the screening interval to 2 years may be reasonable until nodules are detected.

Prevalence of thyroid diseases in familial adenomatous polyposis: a systematic review and meta-analysis

Thyroid cancer (TC) is a known extra-intestinal manifestation and contributes to the mortality and morbidity in patients with familial adenomatous polyposis (FAP). Its exact prevalence is not well established and recent studies have shown an increasing number of TC in this patient population. The prevalence of benign thyroid masses and endocrinologic thyroid disorders are also poorly described. We conducted a systematic review and meta-analysis by using a random-effects model to characterize TC and estimated the prevalence of thyroid diseases in FAP patients. Twelve studies (n = 9821) were included. Pooled prevalence of TC, benign thyroid masses, and endocrinologic thyroid disorders in FAP were 2.6% [95% confidence interval (CI) 1.3-4.8], 48.8% [95% CI 33.8-64.0], and 6.9% [95% CI 4.5-10.3] respectively. Subgroup analyses revealed higher prevalence of TC in studies with fewer participants, studies that used screening ultrasound to diagnose TC, and studies that were published after 2002. TC diagnosis preceded the diagnosis of FAP in 34% of the patients. The means age at diagnosis of FAP and TC were 29 and 31 years, respectively. 95% of the patients were female and the most common pathology was of papillary subtype (83.3%). Most mutations (79.2%) were located at the 5' end of APC gene. In summary, benign thyroid disorders are common in FAP, yet, TC is an uncommon phenomenon. Certain patient subset, such as young female with APC mutation at the 5' end, might benefit from routine surveillance ultrasound.

Inherited variants in genes somatically mutated in thyroid cancer

Background

Tumour suppressor genes when mutated in the germline cause various cancers, but they can also be somatically mutated in sporadic tumours. We hypothesized that there may also be cancer-related germline variants in the genes commonly mutated in sporadic well-differentiated thyroid cancer (WDTC).

Methods

We performed a two-stage case-control association study with a total of 2214 cases and 2108 healthy controls from an Italian population. By genotyping 34 single nucleotide polymorphisms (SNPs), we covered a total of 59 missense SNPs and SNPs located in the 5' and 3' untranslated regions (UTRs) of 10 different genes.

Results

The Italian1 series showed a suggestive association for 8 SNPs, from which three were replicated in the Italian2 series. The meta-analysis revealed a study-wide significant association for rs459552 (OR: 0.84, 95%CI: 0.75–0.94) and rs1800900 (OR: 1.15, 95%CI: 1.05–1.27), located in the APC and GNAS genes, respectively. The APC rs459552 is a missense SNP, located in a conserved amino acid position, but without any functional consequences. The GNAS rs1800900 is located at a conserved 5'UTR and according to the experimental ENCODE data it may affect promoter and histone marks in different cell types.

Conclusions

The results of this study yield new insights on WDTC, showing that inherited variants in the APC and GNAS genes can play a role in the etiology of thyroid cancer. Further studies are necessary to better understand the role of the identified SNPs in the development of WDTC and to functionally validate our in silico predictions.

Desmoid tumors complicating Familial Adenomatous Polyposis: a meta-analysis mutation spectrum of affected individuals

Background

Desmoid tumors are a group of benign, invasive, solid tumors that are relatively rare in the general population, but can occur in up to 21 % of patients with Familial Adenomatous Polyposis (FAP). They can be difficult to treat and have high rates of recurrence even after resection. Our goal with this study was to identify the genetic mutations that put certain patients with FAP at high risk for desmoid tumors and could be future targets for research.

Methods

We performed a search in Pubmed, Ovid Medline and Embase to identify subjects with desmoid tumors and FAP. As a reference group for APC mutations in the unselected FAP population, we used the UMD-APC database referenced in the Orphanet portal which includes APC mutation data on 2040 individuals with FAP.

Results

Mutations were able to be broken down into 7 regions based on previously published data. Mutations in the APC gene from codons 1310 to 2011 were the most common region encompassing 48 % of published desmoid cases and 40 % of the reference population. It had a slightly elevated odds ratio of 1.4 that was statistically significant along with codon region 543-713 that had an odds ratio of 2.0. Using a combination of p-value and CI, the remaining 5 regions did not meet statistical significance as either the p >0.05 or the CI included 1.0. The most common point mutation found was codon 1309 (13.1 %), but it was also the most commonly found mutation in our reference population (12.9 %) and had an odds ratio of 1.0.

Conclusions

There is an increased risk for desmoid tumors in individuals with APC mutations between codons 543-713 and 1310-2011 when compared to a reference population. These patients may benefit from further study to develop surveillance protocols that could improve outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-015-0306-2) contains supplementary material, which is available to authorized users.

Characteristics of benign and malignant thyroid disease in familial adenomatous polyposis patients and recommendations for disease surveillance

BACKGROUND

Familial adenomatous polyposis (FAP) is a hereditary colon cancer syndrome that involves multiple extracolonic organs, including the thyroid. Several studies have estimated the rate of thyroid cancer in FAP to occur at five times the rate of the general population, but no current consensus defines screening for thyroid cancer in this cohort. This study seeks to define the features of benign and malignant thyroid disease in FAP patients, to compare thyroid cancer cases found through screening with those found incidentally, and to propose disease surveillance recommendations.

METHODS

Prospective screening for early thyroid cancer detection with thyroid ultrasound (US) was performed on FAP patients at the time of annual colonoscopy since November 2008. Clinical and US data were reviewed to characterize the observed thyroid nodules. Nonscreening-detected cases (NSD) were found through review of the colon cancer registry database.

RESULTS

Eighteen NSD were found, compared with 15 screening-detected (SD) cases, out of 205 total patients screened (Mage=42 years; 55% female). The mean tumor size was larger in the NSD group than the SD group (p=0.04), and they tended to demonstrate more positive lymph nodes and more complications than the SD group. In the screened cohort, at least one thyroid nodule was detected in 106 (51.7%) patients, with 90% of these seen on initial exam. A total of 40/106 (37.7%) patients required fine-needle aspiration biopsy of a dominant nodule (Msize=14 mm), and 28/40 (70%) of these were performed at the first US visit. Suspicious US features were present in 16/40 (40%) patients, including five sub-centimeter nodules. Cytology and/or nodule US was abnormal in 15/205 screened patients, leading to surgery and revealing 14 papillary and one medullary thyroid cancer.

CONCLUSIONS

Given the age and sex distribution of the screened cohort, this study reveals a higher-than-expected prevalence of both benign and malignant thyroid disease in the FAP population. Additionally, SD cases seemed to consist of smaller-sized cancers that required less radical therapy compared to NSD cases. Since it was found that the initial US in the screening program accounted for the majority of detected nodules (90%) and biopsies (70%), baseline and subsequent thyroid US surveillance is recommended in all FAP patients.

Thyroid cancer complicating familial adenomatous polyposis: mutation spectrum of at-risk individuals

Background

Lifetime risk of thyroid cancer associated with FAP has been reported as 1-2%. The mean age at diagnosis of thyroid carcinoma in FAP has been reported at 28 years. The aims of this paper are to better understand gene mutations associated with thyroid cancer and refine surveillance recommendations for patients with FAP.

Methods

We performed a search in Pubmed, Ovid Medline and Embase with the terms ("Thyroid Gland"[Mesh] OR "Thyroid Neoplasms"[Mesh]) AND "Adenomatous Polyposis Coli"[Meshdenomatous Polyposis Coli"[Mesh] to identify subjects with thyroid cancer and FAP. As a reference group for APC mutations in the unselected FAP population, we used the UMD-APC database referenced in the Orphanet portal, which includes APC mutation data on 2040 individuals with FAP.

Results

There were 115 reported cases of thyroid cancer in patients with FAP (95 female: 11 male) with an average age of 29.2 years. Gene mutation testing results were reported in 48 patients. On comparing the prevalence of APC mutation in the population of FAP patients with thyroid cancer and the prevalence of the same mutation in the reference population an increased odds ratio was evident in individuals harboring an APC mutation at codon 1061 (OR: CI 4.1: 1.7-8.9). Analysis of the prevalence of thyroid cancer in individuals with FAP segregated by the region of the gene affected shows an increased risk of thyroid cancer in individuals harboring mutations proximal to codon 512 (OR 2.6, p 0.0099).

Conclusions

There is increased risk for thyroid cancer in individuals with APC mutations at the 5' end (proximal to codon 528) along with the established high risk group harboring mutation at codon 1061. It is suggested that these patients might benefit from directed surveillance by annual ultrasound from age 18 years onwards.