How to define follicular thyroid carcinoma?

Role of Ultrasound and Ultrasound-Based Prediction Model in Differentiating Follicular Thyroid Carcinoma From Follicular Thyroid Adenoma

OBJECTIVES

This study aims to identify distinct ultrasound (US) characteristics for distinguishing follicular thyroid carcinoma (FTC) from follicular thyroid adenoma (FTA), and construct a user-friendly preoperative risk stratification model for thyroid follicular neoplasms.

METHODS

In this retrospective study, patients diagnosed with pathologically confirmed FTA or FTC and undergoing US examinations between July 2017 and June 2021 were designated as the training cohort, and those from July 2021 to June 2023 were enrolled as the external validation set. We systematically assessed and compared the sonographic and clinical characteristics of FTC and FTA. Univariable and multivariable logistic regression analyses were used to assess the association of US features with FTC in the training set. A prediction nomogram model, incorporating US features independently associated with FTC, was developed and validated externally to assess its performance.

RESULTS

A total of 645 patients (FTA/FTC = 530/115) were included in the training set, while 197 patients (FTA/FTC = 165/32) constituted the validation set. In the training set, solid composition, hypo-echogenicity, irregular margin, calcification, protrusion sign, trabecular formation, absent or thick halo, and mainly central hypervascularity were identified as independent factors associated with FTC. The prediction nomogram model constructed using these variables showed good performance in differentiating FTC from FTA with an area under the curve of 0.948 in the training set and 0.915 in the validation set.

CONCLUSIONS

The preoperative nomogram model constructed based on US features serves as an effective tool for the risk stratification of thyroid follicular neoplasms.

Advances and challenges in thyroid cancer: The interplay of genetic modulators, targeted therapies, and AI-driven approaches

Thyroid cancer continues to exhibit a rising incidence globally, predominantly affecting women. Despite stable mortality rates, the unique characteristics of thyroid carcinoma warrant a distinct approach. Differentiated thyroid cancer, comprising most cases, is effectively managed through standard treatments such as thyroidectomy and radioiodine therapy. However, rarer variants, including anaplastic thyroid carcinoma, necessitate specialized interventions, often employing targeted therapies. Although these drugs focus on symptom management, they are not curative. This review delves into the fundamental modulators of thyroid cancers, encompassing genetic, epigenetic, and non-coding RNA factors while exploring their intricate interplay and influence. Epigenetic modifications directly affect the expression of causal genes, while long non-coding RNAs impact the function and expression of micro-RNAs, culminating in tumorigenesis. Additionally, this article provides a concise overview of the advantages and disadvantages associated with pharmacological and non-pharmacological therapeutic interventions in thyroid cancer. Furthermore, with technological advancements, integrating modern software and computing into healthcare and medical practices has become increasingly prevalent. Artificial intelligence and machine learning techniques hold the potential to predict treatment outcomes, analyze data, and develop personalized therapeutic approaches catering to patient specificity. In thyroid cancer, cutting-edge machine learning and deep learning technologies analyze factors such as ultrasonography results for tumor textures and biopsy samples from fine needle aspirations, paving the way for a more accurate and effective therapeutic landscape in the near future.

Spatially resolved immune microenvironmental profiling for follicular thyroid carcinoma with minimal capsular invasion

Spatial profiles of the tumor-immune microenvironment are associated with disease progression and clinicopathological factors in various cancers. Follicular thyroid carcinoma (FTC) is the second most common thyroid cancer, where the presence of capsular invasion or angioinvasion determines the pathological diagnosis; however, little is known about the immune microenvironment profiles associated with the acquisition of invasive potential of FTC. In this study, we focused on FTC with minimal capsular invasion, and the spatially resolved immune microenvironment of FTC was studied in the discovery (n = 13) and validation cohorts (n = 40). CD8⁺ T cells, helper T cells, regulatory T cells, B cells, natural killer cells, tumor-associated macrophages, CD66⁺ granulocytes, mature dendritic cells, and mast cells were quantitatively evaluated in single tissue sections, via a 12-marker multiplex immunohistochemistry and image cytometry. Cell densities and compositions of immune cells were spatially stratified by six tissue regions including tumor center, subcapsular region, capsular invasion, adjacent stroma of capsular invasion, peritumoral stroma, and adjacent normal. Lymphoid cell lineages in the tumor center and subcapsular regions were significantly lower than those in adjacent normal and peritumoral stroma, potentially related to the lymphoid lineage exclusion from the intratumoral regions of FTC. Interestingly, immune cell composition profiles in the capsular invasive front were distinct from those of intratumoral region. The ratios of T cells to CD66b⁺ granulocytes with capsular invasion were significantly higher than those without capsular invasion, suggesting the presence of a unique immune microenvironment at the invasive front between tumor foci and stroma. In addition, tumor cells at the capsular invasive front showed significantly higher expression of tumor programmed cell death ligand 1 (PD-L1) than those at the tumor center. This study revealed spatial immune profiles associated with capsular invasion of FTC, providing new insights into the mechanisms underlying its development and initial invasion.

[Individualization of the surgical procedure in response to overdiagnosis and overtreatment in differentiated thyroid carcinomas]

BACKGROUND

Advances in diagnostic methods have led to an early detection of thyroid nodules with debatable malignant potential in numerous cases. This can result in a potential overtreatment of thyroid lesions with very good prognosis.

OBJECTIVES

To avoid surgical overtreatment, an individualized, risk-adapted management is required that respects the different tumor biology of the underlying histological entities.

METHODS

The current guidelines of the leading professional societies, the American Thyroid Association (ATA) and the German Association of Endocrine Surgeons (CAEK), were compared and critically studied, to describe risk-adapted, more conservative treatment options for certain types of thyroid neoplasms according to the 2017 WHO definition.

RESULTS

The German CAEK recommends thyroidectomy as a routine operation in the case of thyroid carcinoma. Exceptions are papillary thyroid microcarcinoma and minimally invasive follicular thyroid carcinoma, which can be treated by lobectomy. The ATA proposes an "active surveillance" for papillary thyroid microcarcinoma and lobectomy in cases of differentiated thyroid carcinoma <4 cm in diameter in the absence of clearly predefined risk factors.

CONCLUSIONS

The pre- or intraoperative pathological diagnosis of the underlying tumor entity is the key point, which allows for an adaption of the resection strategy for thyroid malignancy. Depending on the type of carcinoma, the current guidelines of international expert societies allow for parenchyma-sparing operations and, according to the ATA, even an "active surveillance."

Thyroid follicular microcarcinoma

Differentiated thyroid cancers are the most common malignancies arising in thyroid gland. Papillary thyroid cancer presents a very favorable prognosis, while follicular type is slightly more aggressive, mainly for its attitude to hematogenous spreading with distant metastases. Papillary microcarcinoma (10 mm or less) has an excellent prognosis, largely demonstrated, and its management is changed in the last few years, reducing surgical procedure, role of radio iodine ablation (RAI) and TSH suppression. But no effective data are available for follicular thyroid microcarcinoma (mFTC); very few reports and studies are present in literature about mFTC, mainly for its low incidence. Aim of this paper is to review current literature to reach, in absence of evidence, some suggestion in managing mFTC.

Integrated analysis identifies DUSP5 as a novel prognostic indicator for thyroid follicular carcinoma

BACKGROUND

Differentiated thyroid cancer involves thyroid follicular carcinoma (FTC) and papillary thyroid carcinoma (PTC). Patients with FTC have a worse prognosis than those with PTC for early metastasis through blood of FTC. However, the mechanism of poor prognosis of FTC is still unclear. Here, we aim to evaluate the role of DUSP5 in the prognostic evaluation of FTC.

METHOD

We searched the Gene Expression Omnibus (GEO) database for the differentially expressed genes (DEGs) between FTC and PTC, and then combined with survival analysis of cBioPortal database to locate the gene significantly related to prognosis. Tissue microarrays and clinical tissues were used to examine DUSP5 expression by immunohistochemical (IHC) staining between FTC and PTC tissues. In vitro experiment, proliferation, migration and invasion of FTC were observed after regulation of DUSP5 by transfection of siRNA and plasmids, respectively.

RESULTS

After searching the GEO database, 26 DEGs were found. DUSP5 was significantly associated with prognosis of FTC in combination with survival analysis. Data of IHC staining showed lower expression of DUSP5 in FTC compared to PTC tissues. Furthermore, overexpression of DUSP5 inhibited the proliferation, migration and invasion accompanied with low level of MMP9 and Vimentin and high level of E-cadherin. Nevertheless, inhibition of DUSP5 ameliorated above damaging effect on the proliferation, migration and invasion.

CONCLUSION

DUSP5 was differentially expressed in FTC and PTC tissues. Low level of DUSP5 in FTC participates in the high frequency of metastasis, and further contributes to poor prognosis of FTC. DUSP5 could be served as a novel therapeutic target for FTC.

Impact of molecular testing on thyroid nodule neoplastic diagnosis, stratified by 4-cm size, in a surgical series

Whether molecular testing adds diagnostic value to the evaluation of thyroid nodules 4-cm or larger is unknown. The impact of molecular testing on cytopathologic-histopathologic diagnosis of neoplasm (adenoma or malignant), stratified by nodule size Collapse

Key Words

• thyroid diseases
• thyroid cancer

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MESH Headings

• Adenoma/genetics
• Adenoma/pathology
• Biomarkers, Tumor/genetics
• Biomarkers, Tumor/standards
• Biopsy, Fine-Needle/statistics & numerical data
• Genetic Testing/standards
• Genetic Testing/statistics & numerical data
• Humans
• Mutation
• Thyroid Nodule/genetics
• Thyroid Nodule/pathology

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Grants

• UL1TR002494 U.S. Department of Health & Human Services | NIH | National Center for Advancing Translational Sciences (NCATS)
• The Scientific and Technical Research Council of turkey (TUBITAK)

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Affiliation(s)

Rupendra T Shrestha Department of Medicine, University of Minnesota, Minneapolis, USA
Muhammed Kizilgul Department of Medicine, University of Minnesota, Minneapolis, USA Department of Endocrinology and Metabolism, UHS Diskapi Training and Research Hospital, Ankara, Turkey
Maryam Shahi Department of Pathology, University of Minnesota, Minneapolis, USA
Khalid Amin Department of Pathology, University of Minnesota, Minneapolis, USA
Maria R Evasovich Department of Surgery, University of Minnesota, Minneapolis, USA
Lynn A Burmeister Department of Medicine, University of Minnesota, Minneapolis, USA.

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Proposal for an extended pTNM classification of thyroid carcinoma : Commentary on deficits of the 8th edition of the TNM classification

In the 8th edition of the TNM classification of thyroid carcinomas, which was introduced in 2017, carcinomas with minimal extrathyroidal extension are no longer mentioned, which might cause problems. These tumors were explicitly categorized in previous TNM classifications (5-7th editions). Studies on the prognostic relevance of minimal extrathyroidal extension have shown conflicting results. Moreover, the vast majority of these studies retrospectively analyzed only subgroups of thyroid carcinomas (e.g. differentiated thyroid carcinoma, papillary thyroid carcinoma). The proposed subcategorization of the current TNM classification (8th edition) ensures the continuity of the parameter minimal extrathyroidal extension within the TNM categorization of thyroid carcinomas and also offers the possibility to prospectively analyze in a standardized manner the potential biological relevance of minimal extrathyroidal extension in relation to tumor categories (T/pT category).

The surgical dilemma of primary surgery for follicular thyroid neoplasms

Follicular thyroid carcinoma is the second most prevalent form of differentiated thyroid carcinoma, following papillary thyroid carcinoma. Preoperative diagnosis is hampered by the fact that fine-needle aspiration cytology as well as supplemental molecular analysis cannot unambiguously distinguish between follicular thyroid carcinoma and benign follicular thyroid adenoma. The 2017 WHO classification defines three histological subtypes of follicular thyroid carcinoma: minimally invasive (excellent prognosis), encapsulated angioinvasive, and widely invasive type (higher risk of recurrence and metastatic spread). The fact that definite characterization of follicular neoplasms is predominantly a postoperative histological diagnosis (core criteria: capsular, vascular and adjacent tissue invasion) translates into the challenge for the thyroid surgeon to plan preoperatively for presence of malignancy and, if required, to adapt the surgical strategy according to intraoperative (frozen section) or postoperative histological findings. Until improved tools for pre-/intraoperative diagnosis are available, the malignant potential of a follicular thyroid lesion can be assessed by stratifying the patient according to clinical risk factors (presence of metastases, advanced patient age, tumor size). A stepwise, escalating surgical approach with restricted primary resection (hemithyroidectomy) and completion surgery based on the definite histopathology is another option to solve this dilemma. The currently recommended surgical treatment strategies for FTCs as published by ATA, BTA, CAEK and ESES are discussed. There is consensus that prophylactic lymphadenectomy is not required for FTCs and that hemithyroidectomy is sufficient in low-risk FTCs (capsular invasion only) whereas thyroidectomy with postoperative radioiodine therapy is indicated in high-risk FTCs (angioinvasion; widely invasive FTC).

Whole-Exome Sequencing Identifies Two Discrete Druggable Signaling Pathways in Follicular Thyroid Cancer

BACKGROUND

Thyroid cancer is the most common endocrine malignancy, with continuously increasing incidence. Follicular thyroid cancer (FTC) accounts for approximately 10% to 15% of these cases and is known to be associated with several gene mutations. The purpose of this study was to identify novel therapeutic targets in FTC using whole-exome sequencing (WES) and bioinformatics analysis.

STUDY DESIGN

Whole-exome sequencing was performed on 6 established FTC cell lines. Stringent false-proof filtering and exclusion of synonymous and known polymorphisms yielded novel missense, nonsense, and splice-site single nucleotide variants (SNV). Gene variants were analyzed for structural, functional, and evolutionary properties using GO (Gene Ontology), Pfam (Protein Families), and KEGG (Kyoto Encyclopedia of Genes and Genomes) searches by STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) and GORILLA (Gene Ontology enRIchment anaLysis and visuaLizAtion tool) analyses. A false discovery rate of <0.5 was used to denote significantly enriched signaling pathways.

RESULTS

An average of 657 (range 366 to 1,158) SNVs including 31 (range 12 to 53) known cancer driver genes were identified in FTC cell line exomes. The SNV burden, distribution, frequency, and signature followed the known thyroid mutation profiles, without chromosomal bias. Recurrently mutated cancer driver genes included FRG1 (6/6), CDC27, NCOR1, PRSS1 (5/6), AHCTF1, MUC20, PABPC1, and PABPC3 (4/6). Pathway analysis using bioinformatics tools STRING and GORILLA segregated FTC cell lines into 2 druggable signaling groups showing dominant RAS/ERK1-2/AKT and CDK1/CyclinB signaling pathway targets.

CONCLUSIONS

Next-generation sequencing tools can be used to identify druggable signaling targets for precision treatment of FTCs.

Thyroid follicular adenomas and carcinomas: molecular profiling provides evidence for a continuous evolution

Non-autonomous thyroid nodules are common in the general population with a proportion found to be cancerous. A current challenge in the field is to be able to distinguish benign adenoma (FA) from preoperatively malignant thyroid follicular carcinoma (FTC), which are very similar both histologically and genetically. One controversial issue, which is currently not understood, is whether both tumor types represent different molecular entities or rather a biological continuum. To gain a better insight into FA and FTC tumorigenesis, we defined their molecular profiles by mRNA and miRNA microarray. Expression data were analyzed, validated by qRT-PCR and compared with previously published data sets. The majority of deregulated mRNAs were common between FA and FTC and were downregulated, however FTC showed additional deregulated mRNA. Both types of tumors share deregulated pathways, molecular functions and biological processes. The additional deregulations in FTC include the lipid transport process that may be involved in tumor progression. The strongest candidate genes which may be able to discriminate follicular adenomas and carcinomas, CRABP1, FABP4 and HMGA2, were validated in independent samples by qRT-PCR and immunohistochemistry. However, they were not able to adequately classify FA or FTC, supporting the notion of continuous evolving tumors, whereby FA and FTC appear to show quantitative rather than qualitative changes. Conversely, miRNA expression profiles showed few dysregulations in FTC, and even fewer in FA, suggesting that miRNA play a minor, if any, role in tumor progression.

[Proposal for an extended pTNM classification of thyroid carcinoma : Commentary on deficits of the 8th edition of the TNM classification (German version)]

In the 8th edition of the TNM classification of thyroid carcinomas, which was introduced in 2017, carcinomas with minimal extrathyroidal extension are no longer mentioned, which might cause problems. These tumors were explicitly categorized in previous TNM classifications (5-7th editions). Studies on the prognostic relevance of minimal extrathyroidal extension have shown conflicting results. Moreover, the vast majority of these studies retrospectively analyzed only subgroups of thyroid carcinomas (e.g. differentiated thyroid carcinoma, papillary thyroid carcinoma). The proposed subcategorization of the current TNM classification (8th edition) ensures the continuity of the parameter minimal extrathyroidal extension within the TNM categorization of thyroid carcinomas and also offers the possibility to prospectively analyze in a standardized manner the potential biological relevance of minimal extrathyroidal extension in relation to tumor categories (T/pT category).

Identification of CHEK1, SLC26A4, c-KIT, TPO and TG as new biomarkers for human follicular thyroid carcinoma

The search for preoperative biomarkers for thyroid malignancies, in particular for follicular thyroid carcinoma (FTC) diagnostics, is of utmost clinical importance. We thus aimed at screening for potential biomarker candidates for FTC. To evaluate dynamic alterations in molecular patterns as a function of thyroid malignancy progression, a comparative analysis was conducted in clinically distinct subgroups of FTC and poorly differentiated thyroid carcinoma (PDTC) nodules. NanoString analysis of FFPE samples was performed in 22 follicular adenomas, 56 FTC and 25 PDTC nodules, including oncocytic and non-oncocytic subgroups. The expression levels of CHEK1, c-KIT, SLC26A4, TG and TPO were significantly altered in all types of thyroid carcinomas. Based on collective changes of these biomarkers which correlating among each other, a predictive score has been established, allowing for discrimination between benign and FTC samples with high sensitivity and specificity. Additional transcripts related to thyroid function, cell cycle, circadian clock, and apoptosis regulation were altered in the more aggressive oncocytic subgroups only, with expression levels correlating with disease progression. Distinct molecular patterns were observed for oncocytic and non-oncocytic FTCs and PDTCs. A predictive score correlation coefficient based on collective alterations of identified here biomarkers might help to improve the preoperative diagnosis of FTC nodules.

Thick tumor capsule is a valuable risk factor for distant metastasis in follicular thyroid carcinoma

OBJECTIVE

While the biological behavior of follicular thyroid carcinoma (FTC) has been studied in great detail using clinical experience, few studies have investigated pre- or intraoperative factors related to the risk of distant metastasis (DM) among patients with FTC. The aim of this study was to analyze the characteristics of FTC with DM.

METHODS

This study retrospectively investigated 102 patients with FTC who underwent surgery between 1988 and 2013. We compared clinicopathological characteristics between FTC with and without DM.

RESULTS

Univariate analysis revealed nodal metastasis (p=0.045), serum thyroglobulin (Tg) at initial operation (≥1000ng/ml; p<0.0001), widely invasive appearance according to macroscopic findings (p<0.0001), thick tumor capsule (≥1mm; p<0.0001), vascular invasion (p=0.0003), extrathyroidal invasion (p=0.047), and venous tumor embolism (p=0.045) as significant risk factors for DM. Multivariate analysis conducted using pre- and intraoperative factors identified thick tumor capsule (≥1mm), serum Tg at initial operation (≥1000ng/ml), and macroscopically widely invasive appearance as risk factors independently associated with development of DM.

CONCLUSION

Patients with these risk factors should undergo total thyroidectomy and radioactive iodine ablation.

The total number of tissue blocks per centimetre of tumor significantly correlated with the risk of distant metastasis in patients with minimally invasive follicular thyroid carcinoma

BACKGROUND

Given that careful histological examination plays a pivotal role in follicular thyroid carcinoma categorization, we hypothesize that the number of blocks taken at initial specimen review may be associated with survival outcomes of patients initially diagnosed with minimally invasive follicular thyroid carcinoma.

METHODS

A total of 162 patients with confirmed minimally invasive follicular thyroid carcinoma were analyzed. The number of tissue blocks taken from each patient was recorded and the number of blocks per each centimeter of tumor was calculated. A multivariate analysis was conducted to identify independent factors for distant metastasis-free survival.

RESULTS

After a mean follow-up of 197.88 ± 155.39 months, 7 (4.3%) patients developed distant metastasis during follow-up (group II). Relative to those who remained disease-free (group I), group II were significantly older at initial operation (p = 0.022), had larger tumors (p = 0.002) and fewer number of blocks taken/cm of tumor (p = 0.001). However, after adjusting for age at initial operation and tumor size, total number of tissue blocks taken/cm of tumor was the only independent determinant for distant metastasis-free survival (p = 0.049). The 10-year distant metastasis-free survival was significantly better in those who had ≥ 4 blocks/cm of tumor (n = 82) than those with ≤ 3 block/cm of tumor (n = 80) (100 vs. 84.7%, p = 0.005, by log rank).

CONCLUSIONS

Although our study was not able to identify the precise cause for the association between the total number of tissue blocks taken/cm of tumor and distant metastasis-free survival, our data support a more liberal approach in taking tissue blocks on thyroid nodules especially those showing well-differentiated follicular cell differentiation.

[Clinical importance of thyroid gland cytology]

The cytological evaluation of fine needle biopsies (FNB) of the thyroid gland crucially depends on a close cooperation between clinicians and cytopathologists. Scintigraphy, sonography as well as clinical data and patient history are necessary for a correct interpretation of the indications for FNB; moreover, these data are of outstanding importance for cytopathologists for the correct interpretation of the cytomorphological findings. This overview describes the present standards in the acquisition, technical workup and cytopathological interpretation of thyroid gland tissue obtained by FNB, particularly focusing on the rapidly growing relevance of additional molecular pathological investigations to increase the diagnostic accuracy of thyroid FNB.

Current dilemmas in the diagnosis and management of follicular thyroid tumors

Follicular carcinoma (FTC) is a relatively uncommon type of differentiated thyroid carcinoma. Guidelines have often dealt with FTC and papillary thyroid cancer as a single disease. Over the last decade, however, a better understanding of these two types of thyroid cancer indicates that they cannot be analysed together. Neither ultrasonography nor fine-needle aspiration cytology can provide a clear distinction between FTC and follicular adenoma. New molecular diagnostic techniques may be used to identify a subpopulation of follicular neoplasms with a low probability of being malignant. Diagnostic surgery-usually hemithyroidectomy- is recommended for most thyroid follicular lesions without a certain preoperative diagnosis. If FTC is diagnosed most-perhaps not all- patients will require a completion thyroidectomy. While widely invasive FTC usually does not pose diagnostic or therapeutic doubts, consensus on the diagnosis of non-invasive follicular lesions is still lacking. Prognosis of FTC is mostly dependent on local invasion and distant metastasis that, in turn, correlate with tumor size.

Comprehensive Analysis of the Transcriptional and Mutational Landscape of Follicular and Papillary Thyroid Cancers

Follicular thyroid carcinoma (FTC) and benign follicular adenoma (FA) are indistinguishable by preoperative diagnosis due to their similar histological features. Here we report the first RNA sequencing study of these tumors, with data for 30 minimally invasive FTCs (miFTCs) and 25 FAs. We also compared 77 classical papillary thyroid carcinomas (cPTCs) and 48 follicular variant of PTCs (FVPTCs) to observe the differences in their molecular properties. Mutations in H/K/NRAS, DICER1, EIF1AX, IDH1, PTEN, SOS1, and SPOP were identified in miFTC or FA. We identified a low frequency of fusion genes in miFTC (only one, PAX8–PPARG), but a high frequency of that in PTC (17.60%). The frequencies of BRAF^V600E and H/K/NRAS mutations were substantially different in miFTC and cPTC, and those of FVPTC were intermediate between miFTC and cPTC. Gene expression analysis demonstrated three molecular subtypes regardless of their histological features, including Non–BRAF–Non–RAS (NBNR), as well as BRAF–like and RAS–like. The novel molecular subtype, NBNR, was associated with DICER1, EIF1AX, IDH1, PTEN, SOS1, SPOP, and PAX8–PPARG. The transcriptome of miFTC or encapsulated FVPTC was indistinguishable from that of FA, providing a molecular explanation for the similarly indolent behavior of these tumors. We identified upregulation of genes that are related to mitochondrial biogenesis including ESRRA and PPARGC1A in oncocytic follicular thyroid neoplasm. Arm-level copy number variations were correlated to histological and molecular characteristics. These results expanded the current molecular understanding of thyroid cancer and may lead to new diagnostic and therapeutic approaches to the disease.

Recently, The Cancer Genome Atlas proposed an improved classification of the subtypes of papillary thyroid carcinoma (PTC) based on gene expression profiles, which better represents cell signaling and differentiation. However, a molecular characterization of follicular thyroid carcinoma (FTC), which has a greater tendency for hematogenous spread to lung and bone is not yet fully elucidated. In this study, we describe the first RNA sequencing data of minimally invasive FTC (miFTC) and benign follicular adenoma (FA), which cause diagnostic difficulties due to their similar histological features. Additionally, classical PTC and follicular variant of PTC (FVPTC) were sequenced to compare their transcriptional and mutational landscape. BRAF, H/K/NRAS, fusion genes, and copy number variations were associated with tumor histology. Based on gene expression profiles, thyroid tumors were classified as three molecular subtypes regardless of histological subtypes, BRAF–like, RAS–like, and Non–BRAF–Non–RAS. In particular, we found identical gene expression profiles between miFTC, FA, and encapsulated FVPTC. Oncocytic follicular thyroid tumors have gene expression signatures related to mitochondrial biogenesis including ESRRA and PPARGC1A. These results expanded the current molecular understanding of thyroid cancer to its follicular types.

New Concept of the Encapsulated Follicular Variant of Papillary Thyroid Carcinoma and Its Impact on the Bethesda System for Reporting Thyroid Cytopathology: A Single-Institute Experience

BACKGROUND

The encapsulated follicular variant (EFV) of papillary thyroid carcinoma (PTC) is the most discussed entity in thyroid pathology. Recently, the question of whether or not EFV-PTC is a malignant entity has been the subject of renewed discussion in the light of recent molecular and clinical studies. The aim of this study was to analyze the malignancy ratios of each category of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) if EFV-PTC is no longer considered as a malignant entity.

MATERIALS AND METHODS

Data on thyroid fine-needle aspirations (n = 1,886) with surgical follow-up between 1999 and 2014 were studied. EFV-PTC cases constituted 27% (94/343) of the malignant cases.

RESULTS

Malignancy ratios were determined as nondiagnostic, benign, atypia/follicular lesion of undetermined significance, suspicious for follicular neoplasm/follicular neoplasm, suspicious for malignancy, and malignant categories of the TBSRTC in 13, 7, 45, 30, 72 and 98%, respectively. If EFV-PTC was not regarded as malignant, malignancy ratios would decrease to 6.5, 6, 30, 10, 48, and 87% for each category in the same order.

CONCLUSIONS

The current study showed that the most significant decrease in relative malignancy ratios was seen in the suspicious for follicular neoplasm/follicular neoplasm category (66% relative decrease), but all categories represented a considerable decrease.

A novel BAP1 mutation is associated with melanocytic neoplasms and thyroid cancer

Germline mutations in the tumor suppressor gene, BRCA-1 associated protein (BAP1), underlie a tumor predisposition syndrome characterized by increased risk for numerous cancers including uveal melanoma, melanocytic tumors and mesothelioma, among others. In the present study we report the identification of a novel germline BAP1 mutation, c.1777C>T, which produces a truncated BAP1 protein product and segregates with cancer. Family members with this mutation demonstrated a primary clinical phenotype of autosomal dominant, early-onset melanocytic neoplasms with immunohistochemistry (IHC) of these tumors demonstrating lack of BAP1 protein expression. In addition, family members harboring the BAP1 c.1777C>T germline mutation developed other neoplastic disease including thyroid cancer. IHC analysis of the thyroid cancer, as well, demonstrated loss of BAP1 protein expression. Our investigation identifies a new BAP1 mutation, further highlights the relevance of BAP1 as a clinically important tumor suppressor gene, and broadens the range of cancers associated with BAP1 inactivation. Further study will be required to understand the full scope of BAP1-associated neoplastic disease.

Ultrasound-guided core-needle biopsy in thyroid nodules. A study of 676 consecutive cases with surgical correlation

OBJECTIVES

To analyze the diagnostic accuracy of ultrasound-guided core-needle biopsy (CNB) of thyroid nodules.

METHODS

Of 3517 CNBs performed using an 18G spring-loaded device in one institution, we retrospectively reviewed 676 nodules in 629 consecutive patients who underwent surgery. CNB and pathological examination were compared. CNB diagnosis was standardized in four categories: insufficient (I), benign (B), follicular lesion (FOL), and malignant (M). Main outcome measures were predictive positive values (PPV), false positives (FP), and false negatives (FN).

RESULTS

CNB showed a low rate of insufficient and FOL diagnoses (5.8 % and 4.5 %). On surgery, there were eight FNs in 374 benign CNBs and three FPs in 148 malignant CNBs. The 154 nodules classified as FOL in CNB included, at surgery, 122 neoplasms; 28 of them malignant. PPV for malignancy of a malignant CNB was 98 %, and for a CNB diagnosis of FOL 18.2 %. Sensitivity for malignancy if CNB of FOL and M are considered positive was 95.6. Only one major complication was observed.

CONCLUSIONS

CNB is reliable, safe, and accurate to evaluate thyroid nodules and can be an alternative technique to FNA. It has low rate of non-diagnostic and undetermined cases, with high sensitivity and PPV.

KEY POINTS

Thyroid core-needle biopsy (CNB) has high sensitivity and PPV. Pitfalls of CNB are rare. Pitfalls are due to cystic cancer, histological heterogeneity, and mistakes in analysis. CNB is a reliable, safe, and accurate method to approach thyroid nodules. CNB can be used primarily or after insufficient or indeterminate FNA.

[Clinical guideline for management of patients with low risk differentiated thyroid carcinoma]

Incidence of thyroid cancer is increasing in Spain and worldwide. Overall thyroid cancer survival is very high, and stratification systems to reliably identify patients with worse prognosis have been developed. However, marked differences exist between the different specialists in clinical management of low-risk patients with thyroid carcinoma. Almost half of all papillary thyroid carcinomas are microcarcinomas, and 90% are tumors < 2 cm that have a particularly good prognosis. However, they are usually treated more aggressively than needed, despite the lack of adequate scientific support. Surgery remains the gold standard treatment for these tumors. However, lobectomy may be adequate in most patients, without the need for total thyroidectomy. Similarly, prophylactic lymph node dissection of the central compartment is not required in most cases. This more conservative approach prevents postoperative complications such as hypoparathyroidism or recurrent laryngeal nerve injury. Postoperative radioiodine remnant ablation and strict suppression of serum thyrotropin, although effective for the more aggressive forms of thyroid cancer, have not been shown to be beneficial for the treatment of low risk patients, and may impair their quality of life. This guideline provides recommendations from the task force on thyroid cancer of the Spanish Society of Endocrinology and Nutrition for adequate management of patients with low-risk thyroid cancer.

Proteomics, and metabolomics: magnetic resonance spectroscopy for the presurgical screening of thyroid nodules

We review the progress and state-of-the-art applications of studies in Magnetic Resonance Spectroscopy (MRS) and Imaging as an aid for diagnosis of thyroid lesions of different nature, especially focusing our attention to those lesions that are cytologically undetermined. It appears that the high-resolution of High-Resolution Magic-Angle-Spinning (HRMAS) MRS improves the overall accuracy of the analysis of thyroid lesions to a point that a significant improvement in the diagnosis of cytologically undetermined lesions can be expected. This analysis, in the meantime, allows a more precise comprehension of the alterations in the metabolic pathways induced by the development of the different tumors. Although these results are promising, at the moment, a clinical application of the method to the common workup of thyroid nodules cannot be used, due to both the limitation in the availability of this technology and the wide range of techniques, that are not uniformly used. The coming future will certainly see a wider application of these methods to the clinical practice in patients affected with thyroid nodules and various other neoplastic diseases.

Follicular adenomas exhibit a unique metabolic profile. ¹H NMR studies of thyroid lesions

Thyroid cancer is the most common endocrine malignancy. However, more than 90% of thyroid nodules are benign. It remains unclear whether thyroid carcinoma arises from preexisting benign nodules. Metabolomics can provide valuable and comprehensive information about low molecular weight compounds present in living systems and further our understanding of the biology regulating pathological processes. Herein, we applied ¹H NMR-based metabolic profiling to identify the metabolites present in aqueous tissue extracts of healthy thyroid tissue (H), non-neoplastic nodules (NN), follicular adenomas (FA) and malignant thyroid cancer (TC) as an alternative way of investigating cancer lesions. Multivariate statistical methods provided clear discrimination not only between healthy thyroid tissue and pathological thyroid tissue but also between different types of thyroid lesions. Potential biomarkers common to all thyroid lesions were identified, namely, alanine, methionine, acetone, glutamate, glycine, lactate, tyrosine, phenylalanine and hypoxanthine. Metabolic changes in thyroid cancer were mainly related to osmotic regulators (taurine and scyllo- and myo-inositol), citrate, and amino acids supplying the TCA cycle. Thyroid follicular adenomas were found to display metabolic features of benign non-neoplastic nodules and simultaneously displayed a partial metabolic profile associated with malignancy. This finding allows the discrimination of follicular adenomas from benign non-neoplastic nodules and thyroid cancer with similar accuracy. Moreover, the presented data indicate that follicular adenoma could be an individual stage of thyroid cancer development.

AMP-activated protein kinase signaling is upregulated in papillary thyroid cancer

AMP-activated protein kinase (AMPK) is activated by the depletion in cellular energy levels and allows adaptive changes in cell metabolism and cell survival. Recently, our group described that AMPK plays an important role in the regulation of iodide and glucose uptake in thyroid cells. However, AMPK signaling pathway in human thyroid carcinomas has not been investigated so far.

OBJECTIVE

To evaluate the expression and activity of AMPK in papillary thyroid carcinomas.

METHODS

We examined total and phosphorylated AMPK (tAMPK and pAMPK) and phosphorylated acetyl-CoA-carboxylase (pACC) expressions through imunohistochemistry, using a tissue microarray block composed of 73 papillary thyroid carcinomas (PAP CA) or microcarcinomas (PAP MCA) and six adenoma (AD) samples from patients followed at the Federal University Hospital. The expression levels were compared with the non-neoplastic tissues from the same patient. Two different pathologists analyzed the samples and attributed scores of staining intensity and the proportion of stained cells. A total index was obtained by multiplying the values of intensity and the proportion of stained cells (INTxPROP).

RESULTS

tAMPK, pAMPK, and pACC showed a predominant cytoplasmic staining in papillary carcinomas, adenomas, and non-neoplastic thyroid tissues. However, the intensity and the proportion of stained cells were higher in carcinomas, so that a significant increase was found in the INTxPROP score both in PAP CA and PAP MCA, when compared with their respective controls.

CONCLUSION

Our results show unequivocally that AMPK pathway is highly activated in papillary thyroid carcinomas; however, more studies are necessary to understand the pathophysiological significance of AMPK activation in thyroid carcinogenesis.

German Association of Endocrine Surgeons practice guideline for the surgical management of malignant thyroid tumors

INTRODUCTION

Over the past years, the incidence of thyroid cancer has surged not only in Germany but also in other countries of the Western hemisphere. This surge was first and foremost due to an increase of prognostically favorable ("low risk") papillary thyroid microcarcinomas, for which limited surgical procedures are often sufficient without loss of oncological benefit. These developments called for an update of the previous practice guideline to detail the surgical treatment options that are available for the various disease entities and tumor stages.

METHODS

The present German Association of Endocrine Surgeons practice guideline was developed on the basis of clinical evidence considering current national and international treatment recommendations through a formal expert consensus process in collaboration with the German Societies of General and Visceral Surgery, Endocrinology, Nuclear Medicine, Pathology, Radiooncology, Oncological Hematology, and a German thyroid cancer patient support organization.

RESULTS

The practice guideline for the surgical management of malignant thyroid tumors includes recommendations regarding preoperative workup; classification of locoregional nodes and terminology of surgical procedures; frequency, clinical, and histopathological features of occult and clinically apparent papillary, follicular, poorly differentiated, undifferentiated, and sporadic and hereditary medullary thyroid cancers, thyroid lymphoma and thyroid metastases from primaries outside the thyroid gland; extent of thyroidectomy; extent of lymph node dissection; aerodigestive tract resection; postoperative follow-up and surgery for recurrence and distant metastases.

CONCLUSION

These evidence-based recommendations for surgical therapy reflect various "treatment corridors" that are best discussed within multidisciplinary teams and the patient considering tumor type, stage, progression, and inherent surgical risk.

Down-regulation of microRNAs controlling tumourigenic factors in follicular thyroid carcinoma

The molecular determinants of thyroid follicular nodules are incompletely understood and assessment of malignancy is a diagnostic challenge. Since microRNA (miRNA) analyses could provide new leads to malignant progression, we characterised the global miRNA expression in follicular adenoma (FA) and follicular carcinoma (FC). Comparison of carcinoma and adenoma with normal thyroid revealed 150 and 107 differentially expressed miRNAs respectively. Most miRNAs were down-regulated and especially miR-199b-5p and miR-144 which were essentially lost in the carcinomas. Integration of the changed miRNAs with differentially expressed mRNAs demonstrated an enrichment of seed sites among up-regulated transcripts encoding proteins implicated in thyroid tumourigenesis. This was substantiated by the demonstration that pre-miR-199b reduced proliferation when added to cultured follicular thyroid carcinoma cells. The down-regulated miRNAs in FC exhibited a substantial similarity with down-regulated miRNAs in anaplastic carcinoma (AC) and by gene set enrichment analysis, we observed a significant identity between target mRNAs in FC and transcripts up-regulated in AC. To examine the diagnostic potential of miRNA expression pattern in distinguishing malignant from benign nodules we employed a supervised learning algorithm and leave-one-out-cross-validation. By this procedure, FA and FC were identified with a negative predicted value of 83% (data generated by microarray platform) and of 92% (data generated by qRT-PCR platform). We conclude that follicular neoplasia is associated with major changes in miRNA expression that may promote malignant transformation by increasing the expression of transcripts encoding tumourigenic factors. Moreover, miRNA profiling may facilitate the diagnosis of carcinoma vs adenoma.

On the prevalence of the PAX8-PPARG fusion resulting from the chromosomal translocation t(2;3)(q13;p25) in adenomas of the thyroid

The chromosomal translocation t(2;3)(q13;p25) characterizes a subgroup of tumors originating from the thyroid follicular epithelium and was initially discovered in a few cases of adenomas. Later, a fusion of the genes PAX8 and PPARG resulting from this translocation was frequently observed in follicular carcinomas and considered as a marker of follicular thyroid cancer. According to subsequent studies, however, this rearrangement is not confined to carcinomas but also occurs in adenomas, with considerably varying frequencies. Only five cases of thyroid adenomas with this translocation detected by conventional cytogenetics have been documented. In contrast, studies using reverse-transcription polymerase chain reaction (RT-PCR) detected fusion transcripts resulting from that translocation in an average of 8.2% of adenomas. The aim of this study was to determine the frequency of the PAX8-PPARG fusion in follicular adenomas and to use the HMGA2 mRNA level of such tumors as an indicator of malignancy. In cytogenetic studies of 192 follicular adenomas, the t(2;3)(q13;p25) has been identified in only two cases described herein. Histopathology revealed no evidence of malignancy in either case, and, concordantly, HMGA2 mRNA levels were not elevated. In summary, the fusion is a rare event in follicular adenomas and its prevalence may be overestimated in many RT-PCR-based studies.

[When is thyroid fine-needle biopsy most effective?]

The essentially desirable standardisation of various European and American guidelines for the evaluation of thyroid nodules has led to the recommendation to perform fine-needle biopsy (FNB) in all nodules >1 cm in order to detect clinically occult thyroid carcinoma early. However, in iodine-deficient areas such as Germany (where thyroid nodules are found in approximately 25% of the adult population) this recommendation would substantially increase both the number of FNB and thyroid operations without significantly increasing the cancer detection rate. The recommendation for FNB in Germany, therefore, should be restricted to hypofunctioning ("cold") nodules >1 cm.

[Molecular pathology of thyroid tumors]

Molecular genetic analysis is gaining in significance for the differential diagnosis of thyroid tumours. Identifying specific mutations and/or rearrangements offers not only the possibility to distinguish benign from malignant tumours, but also to classify thyroid malignancies more precisely, which can have a substantial influence on the clinical management of patients. In recent years expression analysis of micro-RNA (miRNA) has become an additional tool to improve diagnostic accuracy in thyroid tumours. In addition to its diagnostic contribution, molecular genetic evaluation of thyroid tumours has significantly deepened our understanding of the development, progression and therapy of these tumours.

[Minimally invasive follicular thyroid carcinoma : Not always total thyroidectomy]

Current treatment guidelines for follicular thyroid carcinoma (FTC) recommend total thyroidectomy, lymphadenectomy and radioiodine ablation. Considering the low malignant potential of minimally invasive follicular thyroid carcinoma (MIFTC), a limited radical therapeutic procedure may be adequate. MIFTC is an intensely discussed group of tumors and a review of the literature reveals disagreement among experts concerning the criteria for a distinct definition. Therefore, in 2005 Rosai proposed a clinically more significant classification of FTC based on the extent of capsular and vascular invasion: MIFTC with capsular invasion only, with limited (< or =3) vascular invasion, encapsulated FTC with extensive (>3) vascular invasion and broadly invasive FTC with extensive invasive growth.For the diagnosis of MIFTC a complete investigation of the encapsulated follicular lesion should be performed by the pathologist and examination of at least 10 tissue blocks is mandatory. Due to the excellent prognosis hemithyroidectomy constitutes an adequate therapeutic approach in MIFTC with capsular invasion only and may also be considered for MIFTC with limited vascular invasion. There are no indications for systematic lymphadenectomy.

[Benign thyroid nodule or thyroid cancer?]

Thyroid nodular disease is highly frequent and affects 20-23% of the adult population in Germany. Differential diagnosis of thyroid nodules is directed at exclusion of thyroid autonomy and thyroid cancer. In addition, large nodules/nodular goiters may cause oesophageal and/or tracheal compression. Besides the patient's history and clinical examination, laboratory investigations (TSH-level, calcitonin screening), functional (scintiscan) and morphological imaging (ultrasound, in rare cases also CT without contrast media and MRI), as well as fine needle aspiration biopsy are useful tools in the differential diagnosis. In the past years, major advances have been made in the understanding of the molecular pathogenesis of thyroid tumors. This has led to the possibility of a molecular classification of thyroid tumors and may have prognostic as well as therapeutic impact.

Primary tumour size is a prognostic parameter in patients suffering from differentiated thyroid carcinoma with extrathyroidal growth: results of the MSDS trial

OBJECTIVE

The Multicentre Study Differentiated Thyroid Cancer (MSDS) collective represents a well-defined group of patients with thyroid carcinomas with extrathyroidal extension. The aim of the present study was to evaluate the relationship of the primary tumour size with clinicopathological features as well as the outcome of patients with minimum and extensive extrathyroidal growth (pT3b- and pT4a-tumours; UICC 2002/2003, 6th ed).

METHODS

The tumour diameter was available in 324 out of 351 MSDS patients (244 females, 80 males). Mean age of patients was 47.7±12.0 years (range, 20.1-69.8 years), and the median follow-up was 6.2 years. The relationship between primary tumour size and the following clinicopathological data was investigated: age, gender, histological tumour type (papillary thyroid carcinomas (PTC) versus follicular thyroid carcinomas (FTC)) and UICC/AJCC TNM classification. In addition, the correlation between primary tumour size and event-free and overall survival was assessed.

RESULTS

The FTC of our series were significantly larger than PTC (3.46 vs 1.84 cm; P<0.001). Patients suffering from pT3b-tumours presented with significantly smaller tumour size than those with extensive extrathyroidal growth (pT4a-tumours) (1.9 vs 3.0 cm; P<0.01). All patients with distant metastases suffered from tumours >2 cm. Furthermore, event-free and overall survival were significantly correlated with increasing tumour size (P<0.05). Using multivariate analysis, a pT4a-category and a tumour diameter >2 cm remained independent predictors of survival.

CONCLUSIONS

In patients suffering from differentiated thyroid carcinoma with extrathyroidal growth (pT3b and pT4a), the tumour size is an independent predictor of event-free and overall survival.

Ectopic thyroid presenting as a submandibular mass

Although extremely rare, the presence of ectopic thyroid tissue in the submandibular region should be considered in the differential diagnosis of tissue masses in the cervical region. Diagnosis is confirmed by fine-needle aspiration biopsy and exclusion of malignancy should be confirmed by histopathologic analysis of the lesion. In general, surgery is the treatment of choice. A rare case of ectopic thyroid in the right submandibular region is reported; it was diagnosed after total thyroidectomy and successfully treated through surgery.

Increasing the number of thyroid lesions classes in microarray analysis improves the relevance of diagnostic markers

Background

Genetic markers for thyroid cancers identified by microarray analysis have offered limited predictive accuracy so far because of the few classes of thyroid lesions usually taken into account. To improve diagnostic relevance, we have simultaneously analyzed microarray data from six public datasets covering a total of 347 thyroid tissue samples representing 12 histological classes of follicular lesions and normal thyroid tissue. Our own dataset, containing about half the thyroid tissue samples, included all categories of thyroid lesions.

Methodology/Principal Findings

Classifier predictions were strongly affected by similarities between classes and by the number of classes in the training sets. In each dataset, sample prediction was improved by separating the samples into three groups according to class similarities. The cross-validation of differential genes revealed four clusters with functional enrichments. The analysis of six of these genes (APOD, APOE, CLGN, CRABP1, SDHA and TIMP1) in 49 new samples showed consistent gene and protein profiles with the class similarities observed. Focusing on four subclasses of follicular tumor, we explored the diagnostic potential of 12 selected markers (CASP10, CDH16, CLGN, CRABP1, HMGB2, ALPL2, ADAMTS2, CABIN1, ALDH1A3, USP13, NR2F2, KRTHB5) by real-time quantitative RT-PCR on 32 other new samples. The gene expression profiles of follicular tumors were examined with reference to the mutational status of the Pax8-PPARγ, TSHR, GNAS and NRAS genes.

Conclusion/Significance

We show that diagnostic tools defined on the basis of microarray data are more relevant when a large number of samples and tissue classes are used. Taking into account the relationships between the thyroid tumor pathologies, together with the main biological functions and pathways involved, improved the diagnostic accuracy of the samples. Our approach was particularly relevant for the classification of microfollicular adenomas.

Follicular thyroid carcinoma in an iodine-replete endemic goiter region: a prospectively collected, retrospectively analyzed clinical trial

OBJECTIVE

To determine risk factors for presence of lymph node or distant metastases in patients with follicular thyroid cancer (FTC) at the time of diagnosis and whether there is a relationship between the type of tumor invasion and metastases.

SUMMARY BACKGROUND DATA

FTC often presents distant metastases at the initial diagnosis. As distant metastases are independent prognostic factors in a patient's survival, determination of clinicopathologic characteristics for patients who are at higher risk for developing metastases is of greater clinical importance.

METHODS

The prognostic significance of gender (male vs. female), age (<or=40 years vs. <40 years), tumor size (<or=40 mm vs. >40 mm), number of lesions (uni- vs. multifocality), type of invasion (minimally invasive vs. widely invasive), and oncocytic changes (with vs. without) were analyzed in 207 patients, according to presence of lymph node and distant metastases at the time of initial surgery. According to the type of invasion, the carcinoma-specific survival and the disease-free survival of minimally invasive (MI) and widely invasive (WI) FTC were estimated and compared.

RESULTS

None of the 127 patients with MI growth presented with lymph node metastases but 9.4% distant metastases. Overall risk factors for the presence of lymph node metastases at the initial diagnosis were multifocality (P = 0.02) and widely invasion (P = 0.0001) and for distant metastases age >45 years (P = 0.007), tumor size larger than 40 mm (P = 0.03) and widely invasion (P = 0.0001).WI-FTC patients show larger tumors (P = 0.0001), older age (P = 0.0001), and are presented more frequently in recurrent goiter disease (P = 0.0001). The estimated 10 years carcinoma-specific survival and disease-free survival for MI-tumors were significantly better than for WI-tumors (P = 0.0001).

CONCLUSIONS

Total thyroidectomy is recommended in all patients with FTC because of early distant metastases. Patients with WI-FTC need a more aggressive surgical treatment because of higher tendency for lymph node metastases. MI-FTC has an excellent prognosis with no sign of lymph node metastases, which emphasizes a limited need for nodal surgery.

QPRT: a potential marker for follicular thyroid carcinoma including minimal invasive variant; a gene expression, RNA and immunohistochemical study

Background

The differential diagnosis between follicular thyroid adenoma and minimal invasive follicular thyroid carcinoma is often difficult for several reasons. One major aspect is the lack of typical cytological criteria in well differentiated specimens. New marker molecules, shown by poly- or monoclonal antibodies proved helpful.

Methods

We performed global gene expression analysis of 12 follicular thyroid tumours (4 follicular adenomas, 4 minimal invasive follicular carcinomas and 4 widely invasive follicular carcinomas), followed by immunohistochemical staining of 149 cases. The specificity of the antibody was validated by western blot analysis

Results

In gene expression analysis QPRT was detected as differently expressed between follicular thyroid adenoma and follicular thyroid carcinoma. QPRT protein could be detected by immunohistochemistry in 65% of follicular thyroid carcinomas including minimal invasive variant and only 22% of follicular adenomas.

Conclusion

Consequently, QPRT is a potential new marker for the immunohistochemical screening of follicular thyroid nodules.

Surgical approaches in thyroid cancer and lymph-node metastases

Thyroid cancer collectively encompasses a variety of tumors of disparate morphology and biology. With the exception of radio-iodine therapy for iodine-concentrating well-differentiated thyroid cancers, surgery is the foremost and generally sole effective treatment. Because the growth patterns of these tumors vary tremendously, there is a need to tailor the extent of dissection to the respective tumor entity, especially for less aggressive tumors. No international consensus exists about what precisely constitutes a 'low-risk' or 'high-risk' tumor. Established indications for less-than-total thyroidectomy include small (<or=1 cm), unifocal, and non-metastatic papillary thyroid carcinomas (PTC), and minimally invasive follicular thyroid carcinomas (FTC; invasion of the tumor capsule only). Whether occult multifocal PTC and minimally invasive FTC with histopathological evidence of vascular invasion also fall into the 'low-risk' category remains unclear. For node-positive thyroid cancers, compartment-oriented microdissection is the gold standard of care, whereas the concept of prophylactic lymph-node dissection continues to arouse controversy. Most experts agree that routine lymph-node dissection is unnecessary for low-risk well-differentiated thyroid cancer (DTC). Because occult lymph-node metastases are frequent in high-risk PTC and medullary thyroid carcinoma, compartment-oriented microdissection helps prevent reoperations for 'recurrences' arising from residual nodes, sparing patients the excess morbidity from reoperations in the neck. Because of the looming epidemic of early forms of thyroid cancer, an international consensus is needed regarding (1) the definition of low- versus high-risk tumors; (2) classification of neck nodes; and (3) lymph-node dissection terminology.

Follicular histotypes of oncocytic thyroid carcinomas do not carry mutations of the BRAF hot-spot

BACKGROUND

The BRAF V600E mutation is the most prevalent genetic aberration in papillary thyroid carcinomas (PTCs), and it is found exclusively in RET/PTC-negative tumors. In oncocytic (Hürthle cell, oxyphilic) thyroid tumors, the presence of RET/PTC rearrangements is associated with either the conventional papillary histotype or the "solid" Hürthle cell tumors, whereas all predominantly follicular oncocytic carcinomas do not harbor RET/PTC chimeras. Although 12% of tumors of the follicular variant of PTC carry BRAF mutations, none of the few oncocytic follicular thyroid adenomas (oncoAd) or carcinomas (oncoFTC) published worldwide tested positive. An aspired molecular-based classification of oncocytic thyroid tumors is in need of additional evidence on BRAF mutations in the follicular histotype.

METHODS

A series of 44 oncocytic thyroid tumors with well-documented clinicopathological data was subjected to BRAF mutation analysis (complete exon 15) by automated sequencing.

RESULTS

The series of oncocytic thyroid tumors consisted of 21 adenomas (oncoAds: 17 females, 4 males; mean age, 54.5 years; range, 27-80 years), 20 follicular carcinomas (oncoFTCs: 14 females, 6 males; mean age, 61.4 years; range, 39-80 years), and 3 "classic" papillary carcinomas (oncoPTCs: 3 females; mean age, 58.1 years; range, 46-70 years; 3x T2 tumors). The follicular variants of oncocytic cancers are divided into 11x T2, 5x T3, and 4x T4 tumor stages (International Union Against Cancer [UICC] TNM 5th edition). None of the 44 neoplasms of the presented series demonstrated genetic alterations in the BRAF hot-spot region (exon 15, codons 599-601). Congruently, 0/10 oncoAd and 0/20 oncoFTC described in the literature so far carried BRAF V600E mutations.

CONCLUSIONS

Our results add to the evidence that, in contrast to follicular variants of oncoPTCs, predominantly follicular oncocytic thyroid tumors harbor neither RET/PTC rearrangements nor BRAF mutations. Furthermore, the findings support the concept that oncocytic neoplasms of the thyroid gland are oncocytic counterparts of the respective histotype (adenoma, FTC, PTC, or poorly differentiated thyroid carcinoma) rather than a separate tumor entity. Molecular characterization of oncocytic thyroid malignancies for RET/PTC or BRAF genetic alterations may help with (preoperative) classification and prognostic evaluation of these tumors.

Update on the molecular diagnosis of endocrine tumors: toward -omics-based personalized healthcare?

Genetic advances in endocrine neoplasia provided the paradigm for the practice of clinical cancer genetics: germline RET mutations in multiple endocrine neoplasia type 2. In the last 14 yr, both genetics and -omics advances have occurred, almost exponentially in the last 5 yr. The time has come to reevaluate recent advances in genomic medicine's promise to revolutionize personalized healthcare in the context of endocrine neoplasias. This update focuses on two examples of endocrine neoplasias, those of the thyroid and of the adrenal, and discusses recent advances in germline and somatic genetics and genomics, as they relate to clinical application.

Controversies in thyroid pathology: the diagnosis of follicular neoplasms

Thyroid nodules are common; almost 20% of the population has a palpable thyroid nodule and approximately 70% has a nodule detected by ultrasound. Thyroid cancer is the most frequent endocrine malignancy, and incidence rates have steadily increased over the last decades. Papillary carcinoma (PTC) is the most common malignant neoplasm of the thyroid; the diagnosis of this most frequent type (85-90%) has been increasing, possibly due to changing recognition of morphologic criteria. PTC is defined histologically as a malignant tumor showing evidence of follicular epithelial differentiation and characterized by distinctive nuclear features. However, there are borderline lesions that do not completely fulfill these criteria, making the diagnosis difficult. The use of immunohistochemical and molecular markers adds objective criteria to this confusing and controversial area of pathology. We review the differential diagnosis of well-differentiated follicular thyroid neoplasms and the ancillary techniques and molecular characteristics that have been proposed for application in the diagnosis of PTC.

A molecular expression signature distinguishing follicular lesions in thyroid carcinoma using preamplification RT-PCR in archival samples

Follicular variant of papillary thyroid carcinoma is a lesion that frequently causes difficulties from a diagnostic perspective in the laboratory. The purpose of this study was to interrogate a cohort of archival thyroid lesions using gene expression analysis of a panel of markers proposed to have utility as adjunctive markers in the diagnosis of thyroid neoplasia and follicular variant of papillary thyroid carcinoma in particular. Laser Capture Microdissection was used to procure pure cell populations for extraction. In addition a novel, multiplex preamplification technique was used to facilitate analysis of multiple targets. The panel comprised: HLA-DMA, HLA-DBQ1, CD74, CSNK1G2, IRF3, KRAS2, LYN, MT1K, MT1X, RAB23, TGFB1 and TOP2A, with CDKN1B as an endogenous control. Expression profiles for each target were generated using TaqMan Real-Time PCR. HLA-DMA, HLA-DQB1, MT1X, CSNK1G2 and RAB23 were found to be differentially expressed (P<0.05) when comparing follicular adenoma and follicular variant of papillary thyroid carcinoma. Comparison of follicular adenoma and follicular thyroid carcinoma groups showed significant differential expression for MT1K, MT1X and RAB23 (P<0.05). Comparison of the papillary thyroid carcinoma group (classic and follicular variants) and the follicular adenoma group showed differential expression for CSNK1G2, HLA-DQB1, MT1X and RAB23 (P<0.05). Finally, KRAS2 was found to be differentially expressed (P<0.05) when comparing the papillary thyroid carcinoma and follicular thyroid carcinoma groups. This panel of molecular targets discriminates between follicular adenoma, papillary thyroid carcinoma, follicular variant of papillary thyroid carcinoma and follicular thyroid carcinoma by their expression repertoires. It may have utility for broader use in the setting of fine-needle aspiration cytology and could improve the definitive diagnosis of certain categories of thyroid malignancy.

Novel germline variants identified in the inner mitochondrial membrane transporter TIMM44 and their role in predisposition to oncocytic thyroid carcinomas

Familial Non-Medullary Thyroid Carcinoma (fNMTC) represents 3–7% of all thyroid tumours and is associated with some of the highest familial risks among all cancers, with an inheritance pattern compatible with an autosomal dominant model with reduced penetrance. We previously mapped a predisposing locus, TCO (Thyroid tumour with Cell Oxyphilia) on chromosome 19p13.2, for a particular form of thyroid tumour characterised by cells with an abnormal proliferation of mitochondria (oxyphilic or oncocytic cells). In the present work, we report the systematic screening of 14 candidate genes mapping to the region of linkage in affected TCO members, that led us to identify two novel variants respectively in exon 9 and exon 13 of TIMM44, a mitochondrial inner membrane translocase for the import in the mitochondria of nuclear-encoded proteins. These variants were co-segregating with the TCO phenotype, were not present in a large group of controls and were predicted to negatively affect the protein (exon 9 change) or the transcript (exon 13 change). Functional analysis was performed in vitro for both changes and although no dramatic loss of function effects were identified for the mutant alleles, subtler effects might still be present that could alter Timm44 function and thus promote oncocytic tumour development. Thus we suggest that TIMM44 should be considered for further studies in independent samples of affected individuals with TCO.