Ret oncogene activation in human thyroid neoplasms is restricted to the papillary cancer subtype

Genomic alterations in thyroid cancer: biological and clinical insights

Tumours can arise from thyroid follicular cells if they acquire driver mutations that constitutively activate the MAPK signalling pathway. In addition, a limited set of additional mutations in key genes drive tumour progression towards more aggressive and less differentiated disease. Unprecedented insights into thyroid tumour biology have come from the breadth of thyroid tumour sequencing data from patients and the wide range of mutation-specific mechanisms identified in experimental models, in combination with the genomic simplicity of thyroid cancers. This knowledge is gradually being translated into refined strategies to stratify, manage and treat patients with thyroid cancer. This Review summarizes the biological underpinnings of the genetic alterations involved in thyroid cancer initiation and progression. We also provide a rationale for and discuss specific examples of how to implement genomic information to inform both recommended and investigational approaches to improve thyroid cancer prognosis, redifferentiation strategies and targeted therapies.

Harnessing Immunity to Treat Advanced Thyroid Cancer

The incidence of thyroid cancer (TC) has increased over the past 30 years. Although differentiated thyroid cancer (DTC) has a good prognosis in most patients undergoing total thyroidectomy followed by radioiodine therapy (RAI), 5-10% of patients develop metastasis. Anaplastic thyroid cancer (ATC) has a low survival rate and few effective treatments have been available to date. Recently, tyrosine kinase inhibitors (TKIs) have been successfully applied to RAI-resistant or non-responsive TC to suppress the disease. However, TC eventually develops resistance to TKIs. Immunotherapy is a promising treatment for TC, the majority of which is considered an immune-hot malignancy. Immune suppression by TC cells and immune-suppressing cells, including tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells, is complex and dynamic. Negative immune checkpoints, cytokines, vascular endothelial growth factors (VEGF), and indoleamine 2,3-dioxygenase 1 (IDO1) suppress antitumor T cells. Basic and translational advances in immune checkpoint inhibitors (ICIs), molecule-targeted therapy, tumor-specific immunotherapy, and their combinations have enabled us to overcome immune suppression and activate antitumor immune cells. This review summarizes current findings regarding the immune microenvironment, immunosuppression, immunological targets, and immunotherapy for TC and highlights the potential efficacy of immunotherapy.

Update on Molecular Diagnostics in Thyroid Pathology: A Review

Thyroid nodules are quite common, and the determination of a nodule of concern is complex, involving serum testing, radiology and, in some cases, pathological evaluation. For those nodules that raise clinical concern of neoplasia, fine needle aspiration biopsy is the gold standard for evaluation; however, in up to 30% of cases, results are indeterminate for malignancy, and further testing is needed. Advances in molecular testing have shown it to be of benefit for both diagnostic and prognostic purposes, and its use has become an integral part of thyroid cancer management in the United States and in several global nations. After The Cancer Genome Atlas (TCGA) consortium published its molecular landscape of papillary thyroid carcinoma (PTC) and reduced the "black matter" in PTC from 25% to 3.5%, further work ensued to clarify the remaining fraction not neatly attributed to the BRAF^V600E-like or RAS-like phenotypes of the TCGA. Over the past decade, commercial molecular platforms have been refined as data accrues, and they increasingly cover most genetic variants of thyroid carcinomas. Molecular reporting focuses on the nodule tested, including related clinical information for that nodule (size of nodule, Bethesda category, etc.). This results in a comprehensive report to physicians that may also include patient-directed, clear language that facilitates conversations about nodule management. In cases of advanced or recurrent disease, molecular testing may become essential for devising an individual therapeutic plan. In this review, we focus on the evolution of integrated molecular testing in thyroid nodules, and how our understanding of tumor genetics, combined with histopathology, is driving the next generation of rational patient management, particularly in the context of emerging small, targetable therapeutics.

Strategies for Treatment of Thyroid Cancer

More people are diagnosed with thyroid cancer than any other endocrine tumor. Differentiated thyroid cancer is often treated by removing the thyroid gland (thyroidectomy), iodizing radiation, or inhibiting thyroid stimulating hormone (TSH). Advanced thyroid carcinomas are notoriously resistant to chemotherapy, thus the pursuit of alternative treatments is vital. The best methods for treating individuals with advanced nonmedullary and medullary thyroid carcinomas are discussed in this post. Numerous tyrosine kinase inhibitors and antiangiogenic inhibitors, two types of novel target therapy, have shown promise in studies for individuals with thyroid cancer. Both the positive and unfavourable outcomes of clinical studies of these drugs were addressed. The findings presented here are encouraging, but more study is required to establish whether or not this method is effective in the treatment of thyroid cancer.

RET signaling pathway and RET inhibitors in human cancer

Rearranged during transfection (RET) receptor tyrosine kinase was first identified over thirty years ago as a novel transforming gene. Since its discovery and subsequent pathway characterization, RET alterations have been identified in numerous cancer types and are most prevalent in thyroid carcinomas and non-small cell lung cancer (NSCLC). In other tumor types such as breast cancer and salivary gland carcinomas, RET alterations can be found at lower frequencies. Aberrant RET activity is associated with poor prognosis of thyroid and lung carcinoma patients, and is strongly correlated with increased risk of distant metastases. RET aberrations encompass a variety of genomic or proteomic alterations, most of which confer constitutive activation of RET. Activating RET alterations, such as point mutations or gene fusions, enhance activity of signaling pathways downstream of RET, namely PI3K/AKT, RAS/RAF, MAPK, and PLCγ pathways, to promote cell proliferation, growth, and survival. Given the important role that mutant RET plays in metastatic cancers, significant efforts have been made in developing inhibitors against RET kinase activity. These efforts have led to FDA approval of Selpercatinib and Pralsetinib for NSCLC, as well as, additional selective RET inhibitors in preclinical and clinical testing. This review covers the current biological understanding of RET signaling, the impact of RET hyperactivity on tumor progression in multiple tumor types, and RET inhibitors with promising preclinical and clinical efficacy.

RET Proto-Oncogene Mutational Analysis in 45 Iranian Patients Affected with Medullary Thyroid Carcinoma: Report of a New Variant

Background

The aim of this study was to identify germline mutation of the RET (rearranged during transfection) gene in patients with medullary thyroid carcinoma (MTC) and their first-degree relatives to find presymptomatic carriers for possible prophylactic thyroidectomy. Methods/Patients. We examined all six hot spot exons (exons 10, 11, 13, and 14-16) of the RET gene by PCR and bidirectional Sanger sequencing in 45 Iranian patients with MTC (either sporadic or familial form) from 7 unrelated kindred and 38 apparently sporadic cases. First-degree relatives of RET positive cases were also genotyped for index mutation. Moreover, presymptomatic carriers were referred to the endocrinologist for further clinical management and prophylactic thyroidectomy if needed.

Results

Overall, the genetic status of all of the participants was determined by RET mutation screening, including 61 affected individuals, 22 presymptomatic carriers, and 29 genetically healthy subjects. In 37.5% (17 of 45) of the MTC referral index patients, 8 distinct RET germline mutations were found, including p.C634R (35.3%), p.M918T (17.6%), p.C634Y (11.8%), p.C634F (5.9%), p.C611Y (5.9%), p.C618R (5.9%), p.C630R (5.9%), p.L790F (5.9%), and one uncertain variant p.V648I (5.9%). Also, we found a novel variant p.H648R in one of our apparently sporadic patients.

Conclusion

RET mutation detection is a promising/golden screening test and provides an accurate presymptomatic diagnostic test for at-risk carriers (the siblings and offspring of the patients) to consider prophylactic thyroidectomy. Thus, according to the ATA recommendations, the screening of the RET proto-oncogene is indicated for patients with MTC.

Therapeutic Advances in the Management of Patients with Advanced RET Fusion-Positive Non-Small Cell Lung Cancer

OPINION STATEMENT

Screening for activating driver gene alterations at the time of diagnosis is the standard of care for advanced non-small cell lung cancer (NSCLC). Activating RET fusions are identified in approximately 1-2% of NSCLCs and have emerged as a targetable driver alteration. Selpercatinib and pralsetinib are RET-selective tyrosine kinase inhibitors (TKIs) with encouraging efficacy, intracranial activity, and tolerability that we recommend as first-line therapy. As with use of TKIs in other oncogene-addicted NSCLCs, development of acquired resistance is pervasive and should be specifically delineated through use of repeat tissue biopsy with genetic profiling at the time of disease progression. If an actionable resistance mechanism emerges for which there is a candidate targeted therapy, combination inhibition should be considered. Alternatively, or in the absence of such findings, platinum doublet chemotherapy or particularly platinum-pemetrexed therapy with or without bevacizumab demonstrates a moderate effect.We would not recommend the routine use of nonselective multi-targeted TKIs such as cabozantinib and vandetanib, which have modest activity but limited tolerability due to predictable off-target effects. Single-agent immunotherapy has minimal activity in RET fusion-positive NSCLC. The role of combination chemotherapy and immunotherapy requires further study but may be considered, particularly in the presence of an activating KRAS alteration. While further development of novel RET-selective TKIs may address common RET-specific resistance mutations, they will not have activity against off-target, RET-independent resistance mechanisms. This again highlights the importance of serial biopsy and next-generation sequencing for the rational choice of sequential therapy in RET fusion-positive NSCLC.

Thyroid Carcinoma: Phenotypic Features, Underlying Biology and Potential Relevance for Targeting Therapy

Thyroid carcinoma consists a group of phenotypically heterogeneous cancers. Recent advances in biological technologies have been advancing the delineation of genetic, epigenetic, and non-genetic factors that contribute to the heterogeneities of these cancers. In this review article, we discuss new findings that are greatly improving the understanding of thyroid cancer biology and facilitating the identification of novel targets for therapeutic intervention. We review the phenotypic features of different subtypes of thyroid cancers and their underlying biology. We discuss recent discoveries in thyroid cancer heterogeneities and the critical mechanisms contributing to the heterogeneity with emphases on genetic and epigenetic factors, cancer stemness traits, and tumor microenvironments. We also discuss the potential relevance of the intratumor heterogeneity in understanding therapeutic resistance and how new findings in tumor biology can facilitate designing novel targeting therapies for thyroid cancer.

Molecular therapeutics for anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) represents one of the most lethal human cancers and although this tumor type is rare, ATC accounts for the majority of deaths from thyroid cancer. Due to the rarity of ATC, a comprehensive genomic characterization of this tumor type has been challenging, and thus the development of new therapies has been lacking. To date, there is only one mutation-driven targeted therapy for BRAF-mutant ATC. Recent genomic studies have used next generation sequencing to define the genetic landscape of ATC in order to identify new therapeutic targets. Together, these studies have confirmed the role of oncogenic mutations of MAPK pathway as key drivers of differentiated thyroid cancer (BRAF, RAS), and that additional genetic alterations in the PI3K pathway, TP53, and the TERT promoter are necessary for anaplastic transformation. Recent novel findings have linked the high mutational burden associated with ATC with mutations in the Mismatch Repair (MMR) pathway and overactivity of the AID/APOBEC family of cytidine deaminases. Additional novel mutations include cell cycle genes, SWI/SNF chromatin remodeling complex, and histone modification genes. Mutations in RAC1 were also identified in ATC, which have important implications for BRAF-directed therapies. In this review, we summarize these novel findings and the new genetic landscape of ATC. We further discuss the development of therapies targeting these pathways that are being tested in clinical and preclinical studies.

Oncogene addiction and tumor mutational burden in non-small-cell lung cancer: Clinical significance and limitations

Lung cancer incidence has increased worldwide over the past decades, with non-small cell lung cancer (NSCLC) accounting for the vast majority (85%) of lung cancer specimens. It is estimated that lung cancer causes about 1.7 million global deaths per year worldwide. Multiple trials have been carried out, with the aim of finding new effective treatment options. Lately, special focus has been placed on immune checkpoint (PD1/PD-L1) inhibitors which impact the tumor immune microenvironment. Tumor mutational burden (TMB) has been found to predict response to immune checkpoint inhibitors. Conversely, recent studies have weakened the significance of TMB as a predictor of response to therapy and survival. In this review article, we discuss the significance of TMB, as well as possible limitations. Furthermore, we give a concise overview of mutations frequently found in NSCLC, and discuss the significance of oncogene addiction in lung cancer as an essential driver of tumorigenesis and tumor progression.

Coding Molecular Determinants of Thyroid Cancer Development and Progression

Thyroid cancer is the most common endocrine malignancy. Its incidence and mortality rates have increased for patients with advanced-stage papillary thyroid cancer. The characterization of the molecular pathways essential in thyroid cancer initiation and progression has made huge progress, underlining the role of intracellular signaling to promote clonal evolution, dedifferentiation, metastasis, and drug resistance. The discovery of genetic alterations that include mutations (BRAF, hTERT), translocations, deletions (eg, 9p), and copy-number gain (eg, 1q) has provided new biological insights with clinical applications. Understanding how molecular pathways interplay is one of the key strategies to develop new therapeutic treatments and improve prognosis.

RET EXPRESSION AND ITS CORRELATION WITH CLINICOPATHOLOGIC DATA IN PAPILLARY THYROID CARCINOMA

SUMMARY – The purpose of this study was to analyze the possible prognostic value of RET mutation in papillary thyroid carcinoma and its incidence in the past few decades in our population, due to the increasing incidence of papillary thyroid carcinoma. The present study included 180 patients operated for papillary thyroid carcinoma. The clinical and histopathologic characteristics were analyzed. Paraffin sections of the selected histologic slides were cut again and immunohistochemically stained by the Clone 3F8 P (HIER) from Novocastra (Vision Bio Systems Europe, Newcastle upon Tyne, UK) monoclonal antibody to RET oncoprotein. Univariate analysis indicated sex (p=0.01), histologic subtype (p=0.075) and capsular invasion (p=0.010) to be statistically significant predictors of lymph node metastases, whereas age (p=0.796), tumor size (p=0.556) and intraglandular dissemination (p=0.131) showed no such correlation. The presence of RET mutation (p=0.704) was not a statistically significant predictor of the tumor metastasizing potential. RET mutation (p=0.500) showed no statistically significant correlation with papillary thyroid carcinoma classifed into prognostic groups according to clinicopathologic features either. RET mutation was detected in 30% of 180 papillary thyroid carcinomas. This is the first large study demonstrating that RET mutation incidence in papillary thyroid carcinoma in Croatian population is consistent with the classic distribution of sporadic cases, despite the increased prevalence of papillary thyroid carcinoma in the past few decades.

Mutational Profile of Papillary Thyroid Carcinoma in an Endemic Goiter Region of North India

INTRODUCTION

Mitogen activated protein kinase (MAPK) pathway is regularly altered in papillary thyroid carcinomas (PTCs). Serine/threonine-protein kinase B-Raf (BRAF) V600E mutations were observed very frequently in PTC along with less frequent rat sarcoma (RAS) and rearranged during transfection (RET) gene, also known as RET/PTC translocation. The present study aimed to analyze the mutational profile of PTCs from an endemic Goiter area of North India.

METHODOLOGY

Tissues from 109 PTC patients were used to isolate DNA and RNA. BRAF V600E was detected by restriction fragment length polymorphism-polymerase chain reaction (PCR). RAS mutations were screened by using Sanger's sequencing method. RET/PTC rearrangements were analyzed by real-time PCR.

RESULTS

BRAF V600E mutation was detected in 51.38% (56/109) of PTCs, whereas RAS mutations were less frequent. No RET/PTC rearrangements were observed. BRAF V600E was found to be associated with the aggressive clinicopathological features such as lymph node metastasis, distant metastasis, higher tumor-node-metastasis stages, and high-risk groups.

CONCLUSION

The prevalence of BRAF V600E is high in patients from Indian Subcontinent and found to be associated with aggressive features of PTC. Concomitant mutations of BRAF V600E and RAS mutations impart more aggressiveness to PTCs.

Effects of sorafenib and an adenylyl cyclase activator on in vitro growth of well-differentiated thyroid cancer cells

Well-differentiated thyroid carcinomas have driver mutations involving growth factor receptor-tyrosine kinases (RTKs) or their intracellular signaling pathway, that is, the mitogen-activated protein kinase (MAPK) pathway. Sorafenib is a multikinase inhibitor of RTKs and the MAPK pathway and has recently been used for the treatment of unresectable well-differentiated thyroid carcinoma. In normal thyroid follicular cells, stimulation of the thyroid-stimulating hormone (TSH) receptor activates the cyclic adenosine monophosphate (cAMP) pathway and promotes cell growth as well as hormonal secretion. However, an adenylyl cyclase (AC) activator, forskolin, has been reported to suppress the growth of thyroid carcinoma cells. To clarify the roles of the MAPK and cAMP pathways in proliferation of well-differentiated thyroid carcinoma cells, we compared the effects of sorafenib and forskolin in in vitro models. Sorafenib inhibited constitutive activation of the MAPK pathway, cyclin-dependent kinase 4 (CDK4), and phosphorylated retinoblastoma protein (RB) in 3 well-differentiated carcinoma cell lines, but it did not show sufficiently effective suppression of cell growth. Forskolin significantly suppressed the growth of all 3 cell lines and also activated the cAMP pathway and inhibited expression of cyclin D1. Our results suggest that activation of the cAMP pathway could be more potent than activation of the MAPK pathway in suppressing proliferation of well-differentiated thyroid cancer cells. We postulate that the AC activator suppresses growth of thyroid carcinoma cells through undetermined mechanisms.

Beyond ALK and ROS1: RET, NTRK, EGFR and BRAF gene rearrangements in non-small cell lung cancer

The discovery of gene rearrangements involving the receptor tyrosine kinase genes ALK and ROS1 has revolutionized management of the subset of non-small cell lung cancers characterized by these alterations. The oncogenic fusion proteins expressed in these tumors drive cancer cell growth and survival, and targeted inhibition of this signaling can lead to dramatic and durable responses in patients. While the best characterized gene fusions in non-small cell lung cancer (NSCLC) involve ALK and ROS1, fusions involving other kinases including RET, NTRK, EGFR and BRAF are now established as additional targetable drivers. Here we review data supporting the roles of these fusions as oncogenic drivers, and the potential for targeting these fusions for improved clinical outcomes. These discoveries should encourage multiplexed molecular profiling of lung cancers using next-generation platforms which identify these gene fusions in order to expand treatment options for patients.

The evolution of differentiated thyroid cancer

Differentiated thyroid tumours of follicular cell derivation have traditionally been classified based on architecture, cytology, or both. The features that distinguish the various entities are controversial and diagnostic criteria are inconsistent and often irreproducible. The complexity of classification schemes has not been substantiated by molecular profiling. In this review, a simplistic approach to the diagnosis of well differentiated thyroid neoplasia is provided to challenge the dogma. The proposed classification matches the molecular profiles of these lesions and simplifies the criteria for diagnosis. This approach can be used to support rational treatment algorithms.

Previous External Beam Radiation Treatment Exposure Does Not Confer Worse Outcome for Patients with Differentiated Thyroid Cancer

BACKGROUND

Radiation exposure, especially in childhood, is known to increase the risk for the development of thyroid cancer. However, the prognosis of patients with thyroid cancer with a history of radiation treatment exposure remains unclear.

METHODS

One hundred and sixteen patients with a previous history of radiotherapy in the head and neck region were identified from an institutional database of 3664 patients with differentiated thyroid cancer treated between 1986 and 2010. Using the Kaplan-Meier method, disease-specific survival and recurrence-free survival were compared between patients with (RT; n = 116) and without (No RT; n = 3509) a prior history of radiation exposure.

RESULTS

The median ages of the RT and No RT cohorts were 52 and 47 years. The median follow-up for both groups was 54 months. Patients who had a prior history of radiation treatment exposure were more likely to be male (38.8% vs. 26.9%; p = 0.005) and older than 45 years of age (67.2% vs. 53.9%; p = 0.005). Other patient, tumor, and treatment characteristics were similar between the groups. There was no difference in the five-year disease-specific survival of the RT and No RT patients (97.4% vs. 98.7%; p = 0.798). The five-year recurrence-free survival was also similar between the RT and No RT patients (97.8% vs. 94.9%; p = 0.371).

CONCLUSION

The findings suggest that differentiated thyroid cancer patients with a history of prior radiation treatment exposure have similar outcomes to those with no history of head and neck radiation exposure.

KAOS: a new automated computational method for the identification of overexpressed genes

Background

Kinase over-expression and activation as a consequence of gene amplification or gene fusion events is a well-known mechanism of tumorigenesis. The search for novel rearrangements of kinases or other druggable genes may contribute to understanding the biology of cancerogenesis, as well as lead to the identification of new candidate targets for drug discovery. However this requires the ability to query large datasets to identify rare events occurring in very small fractions (1–3 %) of different tumor subtypes. This task is different from what is normally done by conventional tools that are able to find genes differentially expressed between two experimental conditions.

Results

We propose a computational method aimed at the automatic identification of genes which are selectively over-expressed in a very small fraction of samples within a specific tissue. The method does not require a healthy counterpart or a reference sample for the analysis and can be therefore applied also to transcriptional data generated from cell lines. In our implementation the tool can use gene-expression data from microarray experiments, as well as data generated by RNASeq technologies.

Conclusions

The method was implemented as a publicly available, user-friendly tool called KAOS (Kinase Automatic Outliers Search). The tool enables the automatic execution of iterative searches for the identification of extreme outliers and for the graphical visualization of the results. Filters can be applied to select the most significant outliers. The performance of the tool was evaluated using a synthetic dataset and compared to state-of-the-art tools. KAOS performs particularly well in detecting genes that are overexpressed in few samples or when an extreme outlier stands out on a high variable expression background.

To validate the method on real case studies, we used publicly available tumor cell line microarray data, and we were able to identify genes which are known to be overexpressed in specific samples, as well as novel ones.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1188-1) contains supplementary material, which is available to authorized users.

Application of molecular biology of differentiated thyroid cancer for clinical prognostication

Although cancer outcome results from the interplay between genetics and environment, researchers are making a great effort for applying molecular biology in the prognostication of differentiated thyroid cancer (DTC). Nevertheless, role of molecular characterisation in the prognostic setting of DTC is still nebulous. Among the most common and well-characterised genetic alterations related to DTC, including mutations of BRAF and RAS and RET rearrangements, BRAF^V600E is the only mutation showing unequivocal association with clinical outcome. Unfortunately, its accuracy is strongly limited by low specificity. Recently, the introduction of next-generation sequencing techniques led to the identification of TERT promoter and TP53 mutations in DTC. These genetic abnormalities may identify a small subgroup of tumours with highly aggressive behaviour, thus improving specificity of molecular prognostication. Although knowledge of prognostic significance of TP53 mutations is still anecdotal, mutations of the TERT promoter have showed clear association with clinical outcome. Nevertheless, this genetic marker needs to be analysed according to a multigenetic model, as its prognostic effect becomes negligible when present in isolation. Given that any genetic alteration has demonstrated, taken alone, enough specificity, the co-occurrence of driving mutations is emerging as an independent genetic signature of aggressiveness, with possible future application in clinical practice. DTC prognostication may be empowered in the near future by non-tissue molecular prognosticators, including circulating BRAF^V600E and miRNAs. Although promising, use of these markers needs to be refined by the technical sight, and the actual prognostic value is still yet to be validated.

Evolving approaches in managing radioactive iodine-refractory differentiated thyroid cancer

OBJECTIVE

To discuss the approach to care of patients with advanced differentiated thyroid cancer (DTC), in particular those with radioactive iodine (RAI)-refractory disease, and the transition to systemic treatment.

METHODS

A PubMed search was conducted using the search terms "radioactive iodine-refractory, differentiated thyroid cancer and treatment" restricted to a 2000-2012 timeframe, English language, and humans. Relevant articles were identified from the bibliographies of selected references. Four patient cases are presented to illustrate the clinical course of RAI-refractory DTC.

RESULTS

The current standard of care for early stage DTC could include surgery, RAI in some cases, and thyroid hormone suppression. For advanced RAI-refractory DTC, clinical practice guidelines established by the National Comprehensive Cancer Network and the American Thyroid Association recommend, as one option, the use of systemic therapy, including kinase inhibitors. Numerous trials are underway to evaluate the clinical benefit of these targeted therapies.

CONCLUSION

Preliminary results are encouraging with respect to the clinical benefit of targeted systemic therapies. However, at present there is no consensus on the criteria that define RAI-refractory disease and the optimal timing for transition to systemic therapy. There remains a need to establish common criteria to enhance patient care and enable better comparison across clinical studies.

BRAF T1799A Mutation Occurring in a Case of Malignant Struma Ovarii

Struma ovarii is an extremely rare tumor that occasionally undergoes malignant transformation. Because struma ovarii is composed of thyroid tissue, it is conceivable that the pathogenetic events involved in thyroid follicular transformation may take place also in struma ovarii. The authors describe a case of a classical variant of papillary thyroid carcinoma arising in a struma ovarii of a 22-year-old female. The tumor was heterozygous for BRAF T1799A mutation. No ret/ PTC-1 or ret/PTC-3 rearrangements were detected. This finding would suggest that malignant struma ovarii is similar histologically and genetically to primary papillary thyroid carcinoma.

Genomic and transcriptomic hallmarks of poorly differentiated and anaplastic thyroid cancers

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) are rare and frequently lethal tumors that so far have not been subjected to comprehensive genetic characterization.

METHODS

We performed next-generation sequencing of 341 cancer genes from 117 patient-derived PDTCs and ATCs and analyzed the transcriptome of a representative subset of 37 tumors. Results were analyzed in the context of The Cancer Genome Atlas study (TCGA study) of papillary thyroid cancers (PTC).

RESULTS

Compared to PDTCs, ATCs had a greater mutation burden, including a higher frequency of mutations in TP53, TERT promoter, PI3K/AKT/mTOR pathway effectors, SWI/SNF subunits, and histone methyltransferases. BRAF and RAS were the predominant drivers and dictated distinct tropism for nodal versus distant metastases in PDTC. RAS and BRAF sharply distinguished between PDTCs defined by the Turin (PDTC-Turin) versus MSKCC (PDTC-MSK) criteria, respectively. Mutations of EIF1AX, a component of the translational preinitiation complex, were markedly enriched in PDTCs and ATCs and had a striking pattern of co-occurrence with RAS mutations. While TERT promoter mutations were rare and subclonal in PTCs, they were clonal and highly prevalent in advanced cancers. Application of the TCGA-derived BRAF-RAS score (a measure of MAPK transcriptional output) revealed a preserved relationship with BRAF/RAS mutation in PDTCs, whereas ATCs were BRAF-like irrespective of driver mutation.

CONCLUSIONS

These data support a model of tumorigenesis whereby PDTCs and ATCs arise from well-differentiated tumors through the accumulation of key additional genetic abnormalities, many of which have prognostic and possible therapeutic relevance. The widespread genomic disruptions in ATC compared with PDTC underscore their greater virulence and higher mortality.

FUNDING

This work was supported in part by NIH grants CA50706, CA72597, P50-CA72012, P30-CA008748, and 5T32-CA160001; the Lefkovsky Family Foundation; the Society of Memorial Sloan Kettering; the Byrne fund; and Cycle for Survival.

Follicular cell-derived thyroid cancer

Follicular cell-derived thyroid cancers are derived from the follicular cells in the thyroid gland, which secrete the iodine-containing thyroid hormones. Follicular cell-derived thyroid cancers can be classified into papillary thyroid cancer (80-85%), follicular thyroid cancer (10-15%), poorly differentiated thyroid cancer (<2%) and undifferentiated (anaplastic) thyroid cancer (<2%), and these have an excellent prognosis with the exception of undifferentiated thyroid cancer. The advent and expansion of advanced diagnostic techniques has driven and continues to drive the epidemic of occult papillary thyroid cancer, owing to overdiagnosis of clinically irrelevant nodules. This transformation of the thyroid cancer landscape at molecular and clinical levels calls for the modification of management strategies towards personalized medicine based on individual risk assessment to deliver the most effective but least aggressive treatment. In thyroid cancer surgery, for instance, injuries to structures outside the thyroid gland, such as the recurrent laryngeal nerve in 2-5% of surgeries or the parathyroid glands in 5-10% of surgeries, negatively affect quality of life more than loss of the expendable thyroid gland. Furthermore, the risks associated with radioiodine ablation may outweigh the risks of persistent or recurrent disease and disease-specific mortality. Improvement in the health-related quality of life of survivors of follicular cell-derived thyroid cancer, which is decreased despite the generally favourable outcome, hinges on early tumour detection and minimization of treatment-related sequelae. Future opportunities include more widespread adoption of molecular and clinical risk stratification and identification of actionable targets for individualized therapies.

Targeted therapies in advanced differentiated thyroid cancer

Differentiated thyroid cancer is the most common endocrine malignancy, and its incidence has been rising rapidly over the past 10 years. Although most patients with this disease have an excellent prognosis, a subset develops a more aggressive disease phenotype refractory to conventional therapies. Until recently, there was no effective therapy for these patients. With increasing knowledge of the molecular pathogenesis of thyroid cancer, novel targeted therapies are being developed for this group of patients. Sorafenib and lenvatinib, small-molecule multikinase inhibitors, were approved for the treatment of progressive, symptomatic, radioactive iodine refractory, advanced differentiated thyroid cancer in 2013 and 2015, respectively. This represents a major innovation in the therapy of patients with advanced thyroid cancer. However, these therapies still have many limitations and further research needs to be pursued with the ultimate goal of providing safe and effective personalized therapy for patients with advanced thyroid cancer.

The emerging complexity of gene fusions in cancer

Structural chromosome rearrangements may result in the exchange of coding or regulatory DNA sequences between genes. Many such gene fusions are strong driver mutations in neoplasia and have provided fundamental insights into the disease mechanisms that are involved in tumorigenesis. The close association between the type of gene fusion and the tumour phenotype makes gene fusions ideal for diagnostic purposes, enabling the subclassification of otherwise seemingly identical disease entities. In addition, many gene fusions add important information for risk stratification, and increasing numbers of chimeric proteins encoded by the gene fusions serve as specific targets for treatment, resulting in dramatically improved patient outcomes. In this Timeline article, we describe the spectrum of gene fusions in cancer and how the methods to identify them have evolved, and also discuss conceptual implications of current, sequencing-based approaches for detection.

Break-apart interphase fluorescence in situ hybridization assay in papillary thyroid carcinoma: on the road to optimizing the cut-off level for RET/PTC rearrangements

OBJECTIVE

Chromosomal rearrangements of the RET proto-oncogene is one of the most common molecular events in papillary thyroid carcinoma (PTC). However, their pathogenic role and clinical significance are still debated. This study aimed to investigate the prevalence of RET/PTC rearrangement in a cohort of BRAF WT PTCs by fluorescence in situ hybridization (FISH) and to search a reliable cut-off level in order to distinguish clonal or non-clonal RET changes.

DESIGN

Forty BRAF WT PTCs were analyzed by FISH for RET rearrangements. As controls, six BRAFV600E mutated PTCs, 13 follicular adenomas (FA), and ten normal thyroid parenchyma were also analyzed.

METHODS

We performed FISH analysis on formalin-fixed, paraffin-embedded tissue using a commercially available RET break-apart probe. A cut-off level equivalent to 10.2% of aberrant cells was accepted as significant. To validate FISH results, we analyzed the study cohort by qRT-PCR.

RESULTS

Split RET signals above the cut-off level were observed in 25% (10/40) of PTCs, harboring a percentage of positive cells ranging from 12 to 50%, and in one spontaneous FA (1/13, 7.7%). Overall, the data obtained by FISH matched well with qRT-PCR results. Challenging findings were observed in five cases showing a frequency of rearrangement very close to the cut-off.

CONCLUSIONS

FISH approach represents a powerful tool to estimate the ratio between broken and non-broken RET tumor cells. Establishing a precise FISH cut-off may be useful in the interpretation of the presence of RET rearrangement, primarily when this strategy is used for cytological evaluation or for targeted therapy.

Modeling anaplastic thyroid carcinoma in the mouse

Anaplastic thyroid carcinoma is the least common form of thyroid cancer; however, it accounts for the majority of deaths associated with this family of malignancies. A number of genetically engineered immunocompetent mouse models recapitulating the genetic and histological features of anaplastic thyroid cancer have been very recently generated and represent an invaluable tool to dissect the mechanisms involved in the progression from indolent, well-differentiated tumors to aggressive, undifferentiated carcinomas and to identify novel therapeutic targets. In this review, we focus on the relevant characteristics associated with these models and on what we have learned in terms of anaplastic thyroid cancer biology, genetics, and response to targeted therapy.

Treatment strategies for radioactive iodine-refractory differentiated thyroid cancer

Until recently, no truly effective treatment options have existed for patients with radioactive iodine (RAI)-refractory differentiated thyroid cancer (DTC), a serious disease with poor prognosis. In November 2013, the targeted multikinase inhibitor, sorafenib, was approved for use in these patients based on substantially improved progression-free survival compared with placebo. A number of other targeted agents, including lenvatinib, are being investigated in phase II and phase III trials. With the advent of these new treatment options, practitioners are faced with making important decisions in determining which patients are candidates for systemic treatment and the optimal timing for treatment initiation. Since patients may remain asymptomatic for a protracted period of time, tumor size and growth rate are the primary considerations for making these choices. Proactive management of side effects is also critical in optimizing the effectiveness of treatment. Here we review targeted systemic agents that are either in use or are under investigation for RAI-refractory DTC and provide recommendations on the rationale for initiating systemic treatment and on managing adverse events. Four illustrative case studies are provided.

Novel approaches in anaplastic thyroid cancer therapy

Anaplastic thyroid cancer (ATC), accounting for less than 2% of all thyroid cancer, is responsible for the majority of death from all thyroid malignancies and has a median survival of 6 months. The resistance of ATC to conventional thyroid cancer therapies, including radioiodine and thyroid-stimulating hormone suppression, contributes to the very poor prognosis of this malignancy. This review will cover several cellular signaling pathways and mechanisms, including RET/PTC, RAS, BRAF, Notch, p53, and histone deacetylase, which are identified to play roles in the transformation and dedifferentiation process, and therapies that target these pathways. Lastly, novel approaches and agents involving the Notch1 pathway, nuclear factor κB, Trk-fused gene, cancer stem-like cells, mitochondrial mutation, and tumor immune microenvironment are discussed. With a better understanding of the biological process and treatment modality, the hope is to improve ATC outcome in the future.

Prevalence of RET/PTC1 and RET/PTC3 gene rearrangements in Chennai population and its correlation with clinical parameters

Thyroid cancer is one of the most common endocrine disorders in the world. In India, about 42 million people suffer from various thyroid disorders. However, based on population-based cancer registry (PBCR) and Chennai cancer registry, thyroid cancer is emerging as a common cancer particularly in Chennai. Papillary thyroid carcinoma is considered as the most prevalent cancer constituting about 80-85 % of thyroid malignancies. Rearranged during transfection (RET)/papillary thyroid carcinoma (PTC) gene rearrangements are one of the major genetic alterations found in papillary thyroid carcinoma. This present study aims at estimating the frequency of RET/PTC1 and RET/PTC3 gene rearrangements in Chennai population and investigating the correlation between RET/PTC gene expressions with clinical parameters. Formalin-fixed paraffin-embedded (FFPE) tumor tissues obtained from 30 patients with papillary thyroid carcinoma were analyzed. Initially, to differentiate classic and follicular variants of papillary thyroid carcinoma samples, immunohistochemistry was performed. Thereafter, total RNA was isolated, and quantitative evaluation of RET/PTC1 and RET/PTC3 gene rearrangements by real-time PCR was performed. Chi-square test was performed to understand the correlation between positive and negative mutations of RET/PTC messenger RNA (mRNA) expression with clinical parameters. RET/PTC3 gene rearrangements were identified in 26/30 (86.67 %) cases, and none of the patient in our series had RET/PTC1 gene rearrangements. There was no statistically significant difference observed between positive and negative mutations of RET/PTC3 mRNA expression with clinic pathological parameters. Our results indicate that RET/PTC3 gene rearrangements are the most prevalent form of rearrangements in PTCs of Chennai population.

Diagnostic biomarkers of differentiated thyroid cancer

The incidence of thyroid cancer has been increasing all around the world in the past decades. Early detection is one of the keys to reduce the mortality. Currently, fine-needle aspiration (FNA) guides the management of patients with a thyroid nodule. The use of FNA can reduce unnecessary thyroid surgery by twenty-five percent. However, the prevalence of non-diagnostic and indeterminate cytology from FNA is still high, approximately thirty percent. Many biomarkers were developed to differentiate between the benign and malignant thyroid nodule. This review summarizes each diagnostic biomarker of differentiated thyroid cancer. Sensitivity, specificity, and positive and negative predictive values of individual cytological laboratory need to be considered before implementation of each biomarker. Moreover, follow-up is still mandatory in negative biomarker tests because all genomic and proteomic alterations in thyroid cancer are still unknown.

Tumor suppressor role of the CL2/DRO1/CCDC80 gene in thyroid carcinogenesis

CONTEXT

Thyroid carcinoma is one of the most common malignancies of the endocrine system, and, despite the high frequency of oncogene activation in thyroid neoplastic lesions, the tumor suppressor genes involved in thyroid carcinogenesis remain unidentified. Our previous data implicated a link between the CL2/CCDC80 gene and thyroid cancer.

OBJECTIVE

The objective of the study was to examine the expression of the CL2/CCDC80 gene in human thyroid carcinomas in the attempt to determine whether it plays a role in thyroid carcinogenesis.

DESIGN

We evaluated the expression of CL2/CCDC80 in a large number of thyroid neoplastic tissue samples differing in degree of malignancy. We also investigated the effects of its restoration in 2 human thyroid carcinoma cell lines characterized by very low levels of CL2/CCDC80 expression.

RESULTS

CL2/CCDC80 expression was much lower in almost all the thyroid carcinomas analyzed than in normal thyroid tissues and was lowest in follicular variants of papillary carcinomas. Loss of heterozygosity partially accounted for CL2/CCDC80 down-regulation in thyroid carcinoma samples. Restoration of CL2/CCDC80 expression in the 2 human thyroid anaplastic carcinoma cell lines resulted in a higher susceptibility to apoptosis and suppression of the malignant phenotype. CL2/CCDC80 expression positively regulated the expression of E-cadherin, thereby halting cancer progression.

CONCLUSIONS

These results indicate that CL2/CCDC80 is a putative tumor suppressor gene in thyroid carcinogenesis.

Genetic mutations, molecular markers and future directions in research

Recent molecular studies have described a number of abnormalities associated with the pathogenesis of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development and may serve as prognostic factors and therapeutic targets. A better understanding of the mechanisms involved in thyroid cancer pathogenesis, will hopefully help translate these discoveries to improved patient care.

New treatment in advanced thyroid cancer

Thyroid cancer is the most common endocrine tumor. Thyroidectomy, radioactive iodine, and TSH suppression represent the standard treatment for differentiated thyroid cancer. Since chemotherapy has been shown to be unsuccessful in case of advanced thyroid carcinomas, the research for new therapies is fundamental. In this paper, we reviewed the recent literature reports (pubmed, medline, EMBASE database, and abstracts published in meeting proceedings) on new treatments in advanced nonmedullary and medullary thyroid carcinomas. Studies of many tyrosine kinase inhibitors as well as antiangiogenic inhibitors suggest that patients with thyroid cancer could have an advantage with new target therapy. We summarized both the results obtained and the toxic effects associated with these treatments reported in clinical trials. Reported data in this paper are encouraging, but further trials are necessary to obtain a more effective result in thyroid carcinoma treatment.

Diagnostic and prognostic markers in differentiated thyroid cancer

The MAPK/ERK (mitogen-activated protein kinase/extracellular signal- regulated kinase signaling pathway) and PI3K/Akt (lipid kinase phoshoinositide-3-kinase signaling pathway) play an important role in transmission of cell signals through transduction systems as ligands, transmembrane receptors and cytoplasmic secondary messengers to cell nucleus, where they influence the expression of genes that regulate important cellular processes: cell growth, proliferation and apoptosis. The genes, coding the signaling cascade proteins (RET, RAS, BRAF, PI3K, PTEN, AKT), are mutated or aberrantly expressed in thyroid cancer derived from follicular thyroid cell. Genetic and epigenetic alternations, concerning MAPK/ERK and PI3K/Akt signaling pathways, contribute to their activation and interaction in consequence of malignant follicular cell transformation. Moreover, it is additionally pointed out that genetic, as well as epigenetic DNA changing via aberrant methylation of several tumor suppressor and thyroid-specific genes is associated with tumor aggressiveness, being a jointly responsible mechanism for thyroid tumorigenesis. In the present manuscript the currently developed diagnostic and prognostic genetic/epigenetic markers are presented; the understanding of this molecular mechanism provides access to novel molecular therapeutic strategies.

Evaluation of expression and function of vascular endothelial growth factor receptor 2, platelet derived growth factor receptors-alpha and -beta, KIT, and RET in canine apocrine gland anal sac adenocarcinoma and thyroid carcinoma

Background

Toceranib phosphate (Palladia) has a reported objective response rate of 25% in both canine apocrine gland anal sac adenocarcinoma (AGASACA) and thyroid carcinoma (TC), with stable disease occurring in an additional 50-60% of dogs. The basis for the observed responses to toceranib is not known. The purpose of this study was to evaluate AGASACA and TC samples for the expression and activation of VEGFR2, PDGFRα, PDGFRβ, KIT and RET to assess whether dysregulation of these receptor tyrosine kinases (RTKs) may contribute to the biologic activity of toceranib.

Results

mRNA for VEGFR2, PDGFRα/β, KIT and RET was detected in all AGASACA samples. mRNA for VEGFR2, PDGFRα/β, and KIT was detected in all TC samples, while mRNA for RET was amplified in 10/15 samples. No phosphorylation of VEGFR2, PDGFRα/β, or KIT was observed on the arrays. However, phosphorylation of RET was detected in 54% of the primary AGASACA and 20% of TC. VEGFR2 was expressed in 19/24 primary and 6/10 metastatic AGASACA and 6/15 TC samples. KIT was present in 8/24 primary and 3/10 metastatic AGASACA and 9/15 TC samples. PDGFRα expression was noted in all tumor samples. In contrast PDGFRβ expression was found in only a few tumor samples but was evident in the stroma of all tumor specimens.

Conclusions

Known targets of toceranib are expressed in both AGASAC and TC. Given the observed expression of VEGFR and PDGFRα/β and phosphorylation of RET, these RTKs merit investigation as to their roles in the biology of AGSACA and TC and their contribution to toceranib’s activity.

Thyroid fine needle aspirate: a post-Bethesda update

The Bethesda system for reporting thyroid cytopathology formulated in 2007 has standardized reporting of thyroid cytology specimens and streamlined management algorithms. Although 3 of the categories (benign, malignant, and nondiagnostic) are standardized and improved, the remaining 3 (follicular lesion of undetermined significance, follicular neoplasm, and suspicious for malignancy) remain fraught with interobserver variability and uncertainty regarding management algorithms. Recent and ongoing morphologic and molecular studies that aim to resolve these issues are summarized.

Intracellular signal transduction and modification of the tumor microenvironment induced by RET/PTCs in papillary thyroid carcinoma

RET gene rearrangements (RET/PTCs) represent together with BRAF point mutations the two major groups of mutations involved in papillary thyroid carcinoma (PTC) initiation and progression. In this review, we will examine the mechanisms involved in RET/PTC-induced thyroid cell transformation. In detail, we will summarize the data on the molecular mechanisms involved in RET/PTC formation and in its function as a dominant oncogene, on the activated signal transduction pathways and on the induced gene expression modifications. Moreover, we will report on the effects of RET/PTCs on the tumor microenvironment. Finally, a short review of the literature on RET/PTC prognostic significance will be presented.

RET/PTC rearrangement in benign and malignant thyroid diseases: a clinical standpoint

Cytological examination of fine needle aspiration biopsy is the primary means for distinguishing benign from malignant nodules. However, as inconclusive cytology is very frequent, the introduction of molecular markers in the preoperative diagnosis of thyroid nodules has been proposed in recent years. In this article, we review the clinical implications of preoperative detection of rearrangements of the RET gene (RET/papillary thyroid carcinoma (PTC)) in thyroid nodules. The prevalence of RET/PTC in PTC depends on the histological subtypes, geographical factors, radiation exposure, and detection method. Initially, RET/PTC was considered an exclusive PTC hallmark and later it was also found sporadically in benign thyroid lesions. More recently, the very sensitive detection methods, interphase fluorescence in situ hybridization (FISH) and Southern blot on RT-PCR amplicons, demonstrated that the oligoclonal occurrence of RET rearrangement in benign thyroid lesions is not a rare event and suggested that it could be associated with a faster enlargement in benign nodules. For this reason, RET/PTC cannot be considered as an absolute marker of PTC, and its diagnostic application must be limited to assays able to distinguish between clonal and oligoclonal expression. Detection of RET/PTC by quantitative assays will be useful for diagnostic purposes in cytology specimens when a precise cutoff will be fixed in a clinical setting. Until that time, less sensitive RET/PTC detection methods and FISH analysis remain the most appropriate means to refine inconclusive cytology. Future studies with a long follow-up will further clarify the clinical significance of low level of RET rearrangements in benign nodules.

Molecular genetics and diagnosis of thyroid cancer

Thyroid cancer is a common type of endocrine malignancy, and its incidence has been steadily increasing in many regions of the world. Initiation and progression of thyroid cancer involves multiple genetic and epigenetic alterations, of which mutations leading to the activation of the MAPK and PI3K-AKT signaling pathways are crucial. Common mutations found in thyroid cancer are point mutation of the BRAF and RAS genes as well as RET/PTC and PAX8/PPARγ chromosomal rearrangements. The mutational mechanisms seem to be linked to specific etiologic factors. Chromosomal rearrangements have a strong association with exposure to ionizing radiation and possibly with DNA fragility, whereas point mutations probably arise as a result of chemical mutagenesis. A potential role of dietary iodine excess in the generation of BRAF point mutations has also been proposed. Somatic mutations and other molecular alterations have been recognized as helpful diagnostic and prognostic markers for thyroid cancer and are beginning to be introduced into clinical practice, to offer a valuable tool for the management of patients with thyroid nodules.

Molecular analysis of thyroid tumors

In the recent years, a large number of molecular alterations in thyroid cancer has been discovered and characterized. Some of these markers may have significant diagnostic utility, can be used for tumor prognostication, and serve as potential therapeutic targets. The diagnostic utility of these markers is of particular importance in thyroid fine-needle aspiration samples. Some molecular markers, such as BRAF, offer help in risk stratification and can be potentially used to optimize surgical and postsurgical management of patients with thyroid cancer. This review discusses major molecular alterations known to occur in thyroid cancer, focusing on those markers that have been extensively characterized, carry clinical significance, and are being introduced into pathology practice.

Recent advances in molecular diagnosis of thyroid cancer

Recent molecular studies have described a number of abnormalities associated with the progression and dedifferentiation of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development. In particular, remarkable advances have occurred in several major biological areas of thyroid cancer, including the molecular alterations for the loss of radioiodine avidity of thyroid cancer, the pathogenic role of the MAP kinase and PI3K/Akt pathways and their related genetic alterations, and the aberrant methylation of functionally important genes in thyroid tumorigenesis and pathogenesis. Recognition of these features is crucial to the management of patients with thyroid cancer. Novel treatments are being designed based on our enhanced understanding of this disease process.

Chromosomal rearrangements in post-Chernobyl papillary thyroid carcinomas: evaluation by spectral karyotyping and automated interphase FISH

Structural genomic rearrangements are frequent findings in human cancers. Therefore, papillary thyroid carcinomas (PTCs) were investigated for chromosomal aberrations and rearrangements of the RET proto-oncogene. For this purpose, primary cultures from 23 PTC have been established and metaphase preparations were analysed by spectral karyotyping (SKY). In addition, interphase cell preparations of the same cases were investigated by fluorescence in situ hybridisation (FISH) for the presence of RET/PTC rearrangements using RET-specific DNA probes. SKY analysis of PTC revealed structural aberrations of chromosome 11 and several numerical aberrations with frequent loss of chromosomes 20, 21, and 22. FISH analysis for RET/PTC rearrangements showed prevalence of this rearrangement in 72% (16 out of 22) of cases. However, only subpopulations of tumour cells exhibited this rearrangement indicating genetic heterogeneity. The comparison of visual and automated scoring of FISH signals revealed concordant results in 19 out of 22 cases (87%) indicating reliable scoring results using the optimised scoring parameter for RET/PTC with the automated Metafer4 system. It can be concluded from this study that genomic rearrangements are frequent in PTC and therefore important events in thyroid carcinogenesis.

RET protein expression in papillary renal cell carcinoma

OBJECTIVE

To examine the role of RET in renal malignancy, in particular papillary renal cell carcinoma (RCC).

MATERIALS AND METHODS

A cohort of 111 archival renal samples was used consisting of 94 renal cancers (66 papillary RCC, 18 conventional clear cell carcinoma, 10 chromophobe RCC), 4 benign oncocytomas, and 13 normal kidney tissues. RET protein expression was examined by immunohistochemistry and expression levels were correlated with clinicopathologic and patient survival data.

RESULTS

Positive RET staining was seen in 34/66 (52%) papillary RCCs, 4/10 (40%) chromophobe carcinomas, 4/4 (100%) oncocytomas, and 11/13 (85%) normal kidney samples. All 18 cases of conventional clear cell carcinoma had negative RET staining. RET expression was associated with low Fuhrman nuclear grade.

CONCLUSIONS

RET protein may be contributing in part to an adaptation of a papillary growth pattern in certain renal malignancies. Given the possible therapeutic benefit of small molecule inhibitors of RET activation, further work needs to be done to highlight the functional relevance of RET protein expression in papillary RCC.

RET rearrangements and BRAF mutation in undifferentiated thyroid carcinomas having papillary carcinoma components

AIMS

To elucidate the genetic background of anaplastic transformation, RET rearrangements and BRAF mutation were studied in composite undifferentiated carcinomas (UCs) of the thyroid, which are UCs having papillary carcinoma (PC) components.

METHODS AND RESULTS

Reverse transcription-polymerase chain reaction (RT-PCR) was performed for RET rearrangements and PCR for BRAF mutation in UC and PC components that were microdissected separately from seven composite UCs. Forty-two thyroid cancers with single component histology (14 UCs and 28 PCs) were also studied in the same manner. RET/PTC1 was undetectable in both components from all seven composite UCs, and RET/PTC3 was identified in both components of one composite UC. BRAF mutation was identified in both components from three composite UCs and only in the PC components from two composite UCs. In contrast, in thyroid carcinomas with single component histology, RET/PTC1 was detected in 11% of PCs and in none of the UCs, and RET/PTC3 was not found in any of the tumours studied. BRAF mutation was identified in 82% of PCs and in 21% of UCs.

CONCLUSIONS

The high frequency of BRAF mutation and the absence of RET rearrangements in UC components from composite UCs supports the hypothesis that UCs may actually represent progressive malignant degeneration of a BRAF-mutated, well-differentiated thyroid carcinoma.