Retinoblastoma expression in thyroid neoplasms

Multi-Omics and Management of Follicular Carcinoma of the Thyroid

Follicular thyroid carcinoma (FTC) is the second most common cancer of the thyroid gland, accounting for up to 20% of all primary malignant tumors in iodine-replete areas. The diagnostic work-up, staging, risk stratification, management, and follow-up strategies in patients who have FTC are modeled after those of papillary thyroid carcinoma (PTC), even though FTC is more aggressive. FTC has a greater propensity for haematogenous metastasis than PTC. Furthermore, FTC is a phenotypically and genotypically heterogeneous disease. The diagnosis and identification of markers of an aggressive FTC depend on the expertise and thoroughness of pathologists during histopathological analysis. An untreated or metastatic FTC is likely to de-differentiate and become poorly differentiated or undifferentiated and resistant to standard treatment. While thyroid lobectomy is adequate for the treatment of selected patients who have low-risk FTC, it is not advisable for patients whose tumor is larger than 4 cm in diameter or has extensive extra-thyroidal extension. Lobectomy is also not adequate for tumors that have aggressive mutations. Although the prognosis for over 80% of PTC and FTC is good, nearly 20% of the tumors behave aggressively. The introduction of radiomics, pathomics, genomics, transcriptomics, metabolomics, and liquid biopsy have led to improvements in the understanding of tumorigenesis, progression, treatment response, and prognostication of thyroid cancer. The article reviews the challenges that are encountered during the diagnostic work-up, staging, risk stratification, management, and follow-up of patients who have FTC. How the application of multi-omics can strengthen decision-making during the management of follicular carcinoma is also discussed.

Charting the Unknown Association of COVID-19 with Thyroid Cancer, Focusing on Differentiated Thyroid Cancer: A Call for Caution

BACKGROUND

Conceived of as the "silver lining" of the dark cloud of the coronavirus disease 2019 (COVID-19) pandemic, lessons taught by this catastrophe should be leveraged by medical authorities and policy makers to optimize health care globally. A major lesson is that resilient health systems should absorb sudden shocks incited by overwhelming health emergencies without compromising the continuum of care of chronic diseases, especially of cancer.

METHODS

The present review dissects the association between COVID-19 and thyroid cancer (TC), especially with differentiated TC (DTC), focusing on available data, knowledge gaps, current challenges, and future perspectives.

RESULTS

Obesity has been incriminated in terms of both COVID-19 severity and a rising incidence of TC, especially of DTC. The current conceptualization of the pathophysiological landscape of COVID-19-(D)TC association implicates an interplay between obesity, inflammation, immunity, and oxidative stress. Whether COVID-19 could aggravate the health burden posed by (D)TC or vice versa has yet to be clarified. Improved understanding and harnessing of the pathophysiological landscape of the COVID-19-(D)TC association will empower a mechanism-guided, safe, evidence-based, and risk-stratified management of (D)TC in the COVID-19 era and beyond.

CONCLUSION

A multidisciplinary patient-centered decision-making will ensure high-quality (D)TC care for patients, with or without COVID-19.

Co-Occurrence of Differentiated Thyroid Cancer and Second Primary Malignancy: Correlation with Expression Profiles of Mismatch Repair Protein and Cell Cycle Regulators

Simple Summary

Although the incidence of thyroid cancer is increasing, improvements in treatment have resulted in more patients being confirmed to have a second primary cancer. However, studies on potential biomarkers for predicting the risk of second primary malignancy are extremely limited. Therefore, our objective was to establish molecular biomarkers for the risk prediction of second primary malignancy using routinely collected formalin-fixed paraffin-embedded tissue specimens. Our results suggest that the deficient mismatch repair phenotype, the expression of pRb, and the lack of CDK4 or CDK6 are significantly associated with co-occurrence of nonthyroid malignancy. The predictive value of these immunohistochemical profiles for the co-occurrence of nonthyroid malignancy was also assessed. The combined evaluation of a four-biomarker signature model may provide the most important predictive innovation. Our study proposes the first tissue-based screening tool for risk stratification and further active surveillance in patients with thyroid cancer.

Abstract

Some patients with thyroid cancer develop a second primary cancer. Defining the characteristics of patients with double primary cancers (DPCs) is crucial and needs to be followed. In this study, we examine molecular profiles in DPC. We enrolled 71 patients who received thyroid cancer surgery, 26 with single thyroid cancer (STC), and 45 with DPC. A retrograde cohort was used to develop immunohistochemical expressions of mismatch repair (MMR) proteins and cell-cycle-related markers from tissue microarrays to produce an equation for predicting the occurrence of DPC. The multivariate logistic model of 67 randomly selected patients (24 with STC and 43 with DPC) identified that the expression of deficient MMR (dMMR) (odds ratio (OR), 10.34; 95% confidence interval (CI), 2.17–49.21) and pRb (OR, 62.71; 95% CI, 4.83–814.22) were significantly associated with a higher risk of DPC. In contrast, the expression of CDK4 (OR, 0.19; 95% CI, 0.04–0.99) and CDK6 (OR, 0.03; 95% CI, 0.002–0.44) was significantly associated with a lower risk of DPC. Collectively, dMMR, pRb, CDK4, and CDK6 have a sensitivity of 88.9% (95% CI, 75.1–95.8) and a specificity of 69.2% (95% CI, 48.1–84.9) for occurrence of DPC in all 71 patients. This is the first report to demonstrate the molecular differentiation of STC and DPC. Overall, the integral molecular profile performed excellent discrimination and denoted an exponential function to predict the probability of DPC.

Novel targeted therapies and immunotherapy for advanced thyroid cancers

Thyroid cancer is a frequently encountered endocrine malignancy. Despite the favorable prognosis of this disease, 15–20% of differentiated thyroid cancer (DTC) cases and most anaplastic types, remain resistant to standard treatment options, including radioactive iodine (RAI). In addition, around 30% of medullary thyroid cancer (MTC) cases show resistance after surgery. The evolving understanding of disease-specific molecular therapeutic targets has led to the approval of two targeted therapies (Sorafenib and Lenvatinib) for RAI refractory DTC and another two drugs (Vandetanib and Cabozantinib) for MTC. These advanced therapies exert their effects by blocking the MAPK pathway, which has been widely correlated to different types of thyroid cancers. While these drugs remain reserved for thyroid cancer patients who failed all treatment options, their ability to improve patients’ overall survival remain hindered by their low efficacy and other molecular factors. Among these factors is the tumor’s ability to activate parallel proliferative signaling pathways other than the cascades blocked by these drugs, along with overexpression of some tyrosine kinase receptors (TKR). These facts urge the search for novel different treatment strategies for advanced thyroid cases beyond these drugs. Furthermore, the growing knowledge of the dynamic immune system interaction with tumor microenvironment has revolutionized the cancer immune therapy field. In this review, we aim to discuss the molecular escape mechanisms of thyroid tumors from these drugs. We also highlight novel therapeutic options targeting other pathways than MAPK, including PI3K pathway, ALK translocations and HER2/3 receptors and their clinical impact. We also aim to discuss the usage of targeted therapy in restoring thyroid tumor sensitivity to RAI, and finally turn to extensively discuss the role of immunotherapy as a potential alternative treatment option for advanced thyroid diseases.

Reduced Retinoblastoma Protein Expression Is Associated with Decreased Patient Survival in Medullary Thyroid Cancer

BACKGROUND

The retinoblastoma (RB) transcriptional corepressor 1 protein functions to slow cell-cycle progression. Inactivation of RB by reduced expression and/or hyperphosphorylation allow for enhanced progression through the cell cycle. Murine models develop medullary thyroid carcinoma (MTC) after generalized loss of RB. However, RB expression in MTC has only been evaluated in a small number of tumors, with differing results. The objective of this study was to determine whether reduced expression of RB and/or overexpression of hyperphosphorylated RB predict MTC aggressive behavior.

METHODS

Formalin-fixed, paraffin-embedded primary thyroid tumors and lymph node metastases from MTC patients were evaluated for calcitonin, RB, and phosphorylated RB (pRB) expression by immunohistochemistry. Two expert pathologists evaluated the slides in a blinded manner, and the immunohistochemistry results were compared to disease-specific survival as a primary endpoint.

RESULTS

Seventy-four MTC samples from 56 patients were analyzed in this study, including 51 primary tumors and 23 lymph node metastases. The median follow-up time was 6.75 years after surgery (range 0.64-24.30 years), and the median primary tumor size was 30 mm (range 6-96 mm). Sixty-six percent of cases were classified as stage IV. RB nuclear expression was diffusely present in 88% of primary tumors and 78% of lymph node metastases. Nuclear pRB expression was present in 22% of primary tumors and 22% of lymph node metastases. On univariate analysis, reduced RB (<75% tumor cell staining) trended with lower MTC-specific survival for primary tumor and metastatic nodes (primary tumor hazard ratio = 3.54 [confidence interval 0.81-15.47], p = 0.08; and lymph node hazard ratio = 4.35 [confidence interval 0.87-21.83], p = 0.05). For primary tumors, multivariable analysis showed that low nuclear RB expression was independently associated with worse disease-specific (p = 0.01) and overall (p = 0.02) survival. pRB levels were not associated with survival for either primary tumor or lymph node metastases.

CONCLUSIONS

Reduced RB expression is associated with decreased patient survival in univariate and multivariable analyses, independent from patient age at surgery or advanced TNM stage. Future studies involving larger MTC patient populations are warranted to determine if lower RB expression levels may serve as a biomarker for aggressive disease in patients with MTC.

Animal models of medullary thyroid cancer: state of the art and view to the future

Medullary thyroid carcinoma is a neuroendocrine tumour originating from parafollicular C cells accounting for 5-10% of thyroid cancers. Increased understanding of disease-specific molecular targets of therapy has led to the regulatory approval of two drugs (vandetanib and cabozantinib) for the treatment of medullary thyroid carcinoma. These drugs increase progression-free survival; however, they are often poorly tolerated and most treatment responses are transient. Animal models are indispensable tools for investigating the pathogenesis, mechanisms for tumour invasion and metastasis and new therapeutic approaches for cancer. Unfortunately, only few models are available for medullary thyroid carcinoma. This review provides an overview of the state of the art of animal models in medullary thyroid carcinoma and highlights future developments in this field, with the aim of addressing salient features and clinical relevance.

Immunohistochemical Diagnosis of Thyroid Tumors

Recent insight into the molecular mechanisms of thyroid carcinogenesis has led to studies involving newly directed antibodies. With the introduction of new molecular targeted therapies, these antibodies may represent useful predictors of therapeutic response in tumors unresponsive to radioiodine or insensitive to conventional antitumor therapies. These markers complement the development of markers that are able to discern benign from malignant entities, including hyalinizing trabecular tumors, oncocytic neoplasms, and follicular variant of papillary thyroid carcinoma. The use of antibodies directed to proteins generated by mutated genes may represent a cost-effective method for diagnosing and managing patients affected by thyroid tumors.

p53 suppresses carcinoma progression by inhibiting mTOR pathway activation

Genetic alterations in human cancers and murine models indicate that Rb and p53 have critical tumor suppressive functions in retinoblastoma, a tumor of neural origin, and neuroendocrine tumors including small cell lung cancer and medullary thyroid cancer (MTC). Rb inactivation is the initiating lesion in retinoblastoma and current models propose that induction of apoptosis is a key p53 tumor suppressive function. Genetic studies in mice, however, indicate that other undefined p53 tumor suppressive functions are operative in vivo. How p53 loss cooperates with Rb inactivation to promote carcinogenesis is also not fully understood. In the current study, genetically engineered mice were generated to determine the role of Rb and p53 in MTC pathogenesis and test the hypothesis that p53 suppresses carcinogenesis by inhibiting mTOR signaling. Conditional Rb ablation resulted in thyroid tumors mimicking human MTC, and additional p53 loss led to rapid tumor progression. p53 suppressed tumorigenesis by inhibiting cell cycle progression, but did not induce apoptosis. On the contrary, p53 loss led to increased apoptosis that had to be overcome for tumor progression. mTOR activity was markedly increased in p53 deficient tumors and rapamycin treatment suppressed tumor cell growth identifying mTOR inhibition as a critical p53 tumor suppressive function. Rapamycin treatment did not result in AKT/MAPK activation providing evidence that this feedback mechanism operative in other cancers is not a general response to mTORC1 inhibition. Together, these studies provide mechanistic links between genetic alterations and aberrant signaling pathways critical in carcinogenesis, and identify essential Rb and p53 tumor suppressive functions in vivo.

Clinical implications of molecular markers in follicular cell-derived thyroid cancer

The increasing use/applications of molecular biology techniques have provided new insights on the genetic changes that underlie carcinogenesis and tumor progression in thyroid cancer. Molecular analysis may improve the histopathologic evaluation of follicular cell-derived thyroid carcinoma, not only elucidating some unresolved problems related to the diagnosis and disease prognosis, but also by improving patient management. Besides increasing our comprehension of cancer biology, either genetic alterations or gene expression profiles implicated in thyroid carcinogenesis shed new light on innovative diagnostic procedures as well as on targeted therapies.

Human thyroid tumours, the puzzling lessons from E7 and RET/PTC3 transgenic mice

Human rearranged RET/PTC3 (papillary thyroid carcinoma) proto-oncogene and high-risk human papillomavirus (HPV) type 16 E7 oncogene induces in the mouse a neoplastic transformation of thyroid follicular cells. We present a detailed immuno-histological study (170 mouse thyroids: RET/PTC3, E7, wild type, 2- to 10-month-old) with cell cycle proliferation and signalling pathway indicators. The characteristics of both models are different. There is an 'oncogene dependent' cellular signature, maintained at all studied ages in the E7 model, less in the RET/PTC3 model. During tumour development a large heterogeneity occurred in the Tg-RET/PTC3 model within a same tumour or within a same thyroid lobe. The Tg-E7 model was less heterogeneous, with a dominant goitrous pattern. The solid tumour already described in the RET/PTC3 models associated with cribriform patterns, suggested 'PTC spindle cell changes' as in humans PTC rather than the equivalent of the solid human PTC. Proliferation and apoptosis in the two thyroid models are related to the causal oncogene rather than reflect a general tumorigenic process. The thyroids of RET/PTC3 mice appeared as a partial and transient model of human PTCs, whereas the Tg-E7 mice do not belong to the usual PTC type.

ONYX-411, a conditionally replicative oncolytic adenovirus, induces cell death in anaplastic thyroid carcinoma cell lines and suppresses the growth of xenograft tumors in nude mice

Anaplastic thyroid carcinoma (ATC) is the most aggressive thyroid cancer variant, accounting for 1-2% of all cases, but 33% of deaths, and exhibiting an average life expectancy of 5 months. ATC is largely unresponsive to radioactive iodine, chemotherapy, external beam radiation or surgery, underscoring the need for new and effective therapies. We evaluated the therapeutic potential of an oncolytic adenovirus, ONYX-411, that replicates selectively in and kills cells with dysfunction of the retinoblastoma (RB) pathway. In the present study, we report that ONYX-411 is able to induce cell death in eight human anaplastic carcinoma cell lines in vitro. The cytopathic effect of the virus is specific to cells with RB dysfunction, which appears to be frequent in ATC. We confirmed the expression of the coxsackie adenovirus receptor, CAR, in all ATC cell lines, demonstrating the potentially universal application of this oncolytic viral therapy to ATC. In addition, the growth of xenograft tumors induced in athymic mice with the ARO and DRO cell lines was significantly reduced by ONYX-411 treatment. These results indicate that ONYX-411 can be a potential therapeutic agent for the treatment of ATC, rendering this class of conditionally replicating adenoviruses an attractive candidate for clinical trials.

Importance of Ezh2 polycomb protein in tumorigenesis process interfering with the pathway of growth suppressive key elements

An understanding of the mechanisms that uncover the dynamic changes in the distribution of the chromatin modifying enzymes and regulatory proteins on their target loci could provide further insight into the phenomenon of malignant transformation. Based on the current available data, it seems more and more clear that an abnormal expression of Ezh2, a member of the Polycomb group (PcG) protein, may be involved in the tumorigenesis process, in addition, different studies identify Ezh2 as a potential marker that distinguish aggressive prostate and breast cancer from indolent one. Recent investigation show that ectopic expression of Ezh2 provides proliferative advantage to primary cells through interaction with the pathways of key elements that control cell growth arrest and differentiation, like members of the retinoblastoma (Rb) family. Here, we outline how these pathways converge and we review the recent advances on the molecular mechanisms that promote cell cycle progression through deregulation of Ezh2 protein level, providing novel links between cancer progression and chromatin remodeling machineries.

DNA hypermethylation status of multiple genes in papillary thyroid carcinomas

OBJECTIVE

The aim of this study was hypermethylation of multiple genes for papillary thyroid carcinomas (PTCs).

METHODS

We examined 39 lesions using methylation-specific PCR to assess hypermethylation in genes, including p16(INK4a), p14(ARF), RB1, p27(Kip1)and 0(6)-MGMT. Homozygous deletions of p16(INK4a) and p14(ARF) were investigated by differential PCR, all with reference to clinicopathological factors.

RESULTS

We found methylation of p16(INK4a) in 35.9% (14/39); p14(ARF) in 2.6% (1/39); RB1 in 23.1% (9/39); p27(Kip1) in 15.4% (6/39),and 0(6)-MGMT in 15.4% (6/39). Hypermethylation of at least one of these genes was apparent in 66.7% (26/39). Homozygous deletions of p14(ARF) and p16(INK4a) were detected in 7.7 (3/39) and 2.6% (1/39), respectively. In cases with p16(INK4a) alterations, tumors were significantly increased. A history of chronic thyroid disease and lymphocytic infiltration was significantly associated with p14(ARF) alterations, without regional lymph node metastases.

CONCLUSIONS

Our data suggest that alterations in p16(INK4a), mainly hypermethylation, may be linked to tumor growth but not tumor development, while alterations in p14(ARF) may contribute to the induction of chronic inflammation-related PTCs.

Genetic interaction between Rb and N-ras: differentiation control and metastasis

The retinoblastoma tumor suppressor gene, Rb, and the ras proto-oncogenes regulate various cellular processes, including differentiation and proliferation. Rb and ras genetically interact to positively influence differentiation in the mouse. This genetic interaction between Rb and ras also affects tumor development, either positively or negatively depending on cell type. Loss of one or two N-ras alleles allows medullary thyroid (C cell) adenomas occurring in Rb heterozygous mice to progress to metastatic carcinomas, an event associated with C cells displaying a less-differentiated phenotype. Here, we discuss the genetic interaction between Rb and ras and the development of a mouse model of medullary thyroid carcinoma.

Genetic alterations in thyroid cancer: the role of mouse models

Thyroid carcinomas are the most common endocrine neoplasms in humans, with a globally increasing incidence. Thyroid follicular cells and neuroendocrine (parafollicular) C cells are each susceptible to neoplastic transformation, resulting in thyroid cancers of differing phenotypes with unique associated genetic mutations and clinical outcomes. Over the past 15 years, several sophisticated genetically engineered mouse models of thyroid cancer have been created to further our understanding of the genetic events leading to thyroid carcinogenesis in vivo. The most significant mouse models of papillary, follicular, anaplastic, and medullary thyroid carcinoma are highlighted, with particular emphasis on the relationship between the relevant oncogenes in these models and genetic events in the naturally occurring human disease. Limitations of each model are presented, and the need for additional models to better recapitulate certain aspects of the human disease is discussed.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

How to define follicular thyroid carcinoma?

The appropriate diagnosis of follicular thyroid carcinoma (FTC) still depends on its histological discrimination from follicular adenoma (including the distinction of benign from malignant oncocytic variants), papillary thyroid carcinoma (particularly from the follicular variants) and poorly differentiated thyroid carcinoma. The use of immunohistochemical markers contributed only marginally to better defining FTC. The introduction of the micro array technique, however, may offer the possibility of getting a better insight into the natural history, as well as predicting the clinical course, of a given thyroid nodule. This review attempts to recapitulate common standards in the diagnosis of FTC, to summarise current molecular data available to distinguish FTC from other benign and malignant tumours and, finally, to outline future perspectives to define FTC on its specific genetic features.

New prognostic scales LAST-1 and LAST-2: supporting prediction and staging of thyroid cancer

INTRODUCTION

Epidemiologically, thyroid gland tumors are lesions of the highest importance among endocrine tumors in humans. Although the results of surgical treatment of the highly differentiated (follicular and papillary) tumors seem to be satisfactory, treatment of the poorly differentiated (medullary and anaplastic) tumor still demands clinical and basic investigations. In this study the authors sought to evaluate clinical and molecular factors that could contribute to preoperative detection of more advanced thyroid cancers (i.e., those that exhibit extrathyroid spread and lymph node invasion).

METHODS

A total of 27 patients operated on for thyroid cancer were evaluated according to age, sex, time from the onset of the disease, cytogenetic changes, and loss of heterozygosity (LOH) in 14 microsatellite markers. The output variables were defined according to postoperative findings and the TNM 2002 score. The T1-2 N0 M0 cases were defined as local malignancy (LM); and T3-4 any N any M, any T N1 any M, or any T any N M1 were considered advanced malignancy (AM). The control groups consisted of 25 patients with multinodular goiter (MNG) and 32 patients with follicular adenoma (FA). In all cases, clinical and molecular data similar to those listed above were collected, excluding staging and follow-up information.

RESULTS

There was no predominant specific type of chromosomal aberration observed and no marker lost in more than five patients (18%). The logistic regression identified three input variables as contributing significantly to the dichotomized outcome measure (LM vs. AM): LOH in any of the examined loci, age of the patient at the presentation, and the sex of the patient. Furthermore, discriminant analysis revealed four input variables differentiating among TC, FA, and MNG patients. Based on the multivariate analysis results, two numeric prognostic scales were fashioned: LAST-1, a scale applicable to differentiation of thyroid cancers at different degrees of clinical advancement; and LAST-2, a scale applicable to differentiation of any thyroid lumps.

CONCLUSIONS

It was concluded that LOH and the age and sex of the patients can provide sufficient data to predict thyroid cancer with a high degree of clinical advancement. LAST-1 scale is a reliable tool for identifying these patients. The LAST-2 scale gives supportive information about the character of thyroid lumps, distinguishing TC from MNG and FA.

Patterns of Cyclin E, Retinoblastoma Protein, and p21Cip1/WAF1 Immunostaining in the Oncogenesis of Papillary Thyroid Carcinoma

Purpose: Uncontrolled cell proliferation, a hallmark of cancer, may result from an increased expression of cell cycle up-regulators, and/or from a reduced expression of cell cycle down-regulators. In the present study, we analyzed, by immunohistochemistry, the expression of a panel of three proteins: cyclin E and two cell cycle inhibitors, p21Cip1/WAF1 and retinoblastoma protein (pRb) product, in different stages of papillary thyroid carcinomas (PTC).

Experimental Design: We investigated immunostaining patterns of the proteins in question in 51 resected PTC in pathologic stages, ranging from pT1a to pT4, taking into consideration their relation to clinicohistopathologic factors.

Results: We observed a significant, progressive loss of expression of p21Cip1/WAF1 with advancing tumor grade. The differences reached values of significance between pT1a [papillary thyroid microcarcinomas (PMC)] and pT2 and between PMC and pT4 stages of PTC. pRb presented a similar immunostaining pattern to that of p21Cip1/WAF1 and the differences reached values of significance between pT1a and pT2, and between PMC and pT4 stages of PTC. The results of cyclin E immunostaining corresponded to our recently published result, and a negative correlation was observed between the immunostaining index of cyclin E and pRb.

Conclusions: The results of the present study suggest that cyclin E expression and suppression of pRb and p21Cip1/WAF1 may be characteristic patterns of immunostaining for PTC with a tendency to early metastasizing. If our results are confirmed in a larger study, the diagnostic panel, constructed of the antibodies against these proteins, may become a valuable tool in predicting the metastatic potential in PTC.

Fine-Needle Aspiration of Thyroid Nodules: Past, Present, and Future

OBJECTIVE

To present a review of the traditional and more recent techniques and applications of thyroid fine-needle aspiration biopsy.

METHODS

We describe the cytologic features and differential diagnoses of various thyroid lesions, outline recommendations for diagnostic categories, and discuss new techniques that have shown some promise in the diagnosis of thyroid nodule fine-needle aspiration specimens.

RESULTS

Fine-needle aspiration biopsy of the thyroid has proved to be an excellent diagnostic tool in the initial management of thyroid nodules. Numerous studies have shown its high sensitivity and specificity in diagnosing malignant tumors of the thyroid, especially papillary thyroid carcinoma. As with other diagnostic tests, however, its effectiveness is highly dependent on the expertise of the operator performing the procedure and the adequacy of the specimen for interpretation of the cytomorphologic features. On-site evaluation of thyroid specimens promotes adequate specimen sampling and reduces the incidence of nondiagnostic specimens. Diagnostic reports on thyroid fine-needle aspiration should include patient demographics and pertinent clinical history, site and size of the thyroid nodule, mode of aspiration, number of needle passes, assessment of specimen adequacy, diagnosis, and recommendations. Although immunohistochemical and molecular markers have received considerable attention recently, additional studies are needed before they can be used to separate benign from malignant follicular thyroid lesions.

CONCLUSION

Overall, fine-needle aspiration biopsy of thyroid nodules has proved to be sensitive, specific, and well accepted by patients because of minimal discomfort and complications.

Hypermethylation, but not LOH, is associated with the low expression of MT1G and CRABP1 in papillary thyroid carcinoma

We previously obtained gene expression profiles of 8 matched papillary thyroid carcinoma (PTC) and normal tissues using DNA microarrays. To identify novel tumor suppressor genes involved in thyroid carcinogenesis, we here analyze genes showing lower expression in PTC tumors than in normal thyroid tissues. A search for loss of heterozygosity (LOH) in 49 regions that harbor consistently down-regulated genes revealed LOH in only 4 regions and in just a very small number of tumors. To determine whether the underexpression might be due to promoter methylation, we used combined bisulfite restriction analysis and bisulfite sequencing to study 7 underexpressed genes. Loss of expression of MT1G and CRABP1 is accompanied by hypermethylation in the 5' regions of these genes, but methylation was not seen in other genes tested. Combined treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-Aza-dC) and the histone deacetylase inhibitor trichostatin A (TSA) resulted in demethylation and re-expression of the MT1G gene in the cell line K2. Treatment with 5-Aza-dC alone restored CRABP1 expression in a colorectal cancer cell line, SW48. In conclusion, LOH is a remarkably rare mechanism of loss of gene function in PTC. In contrast, hypermethylation of promoter CpG islands seems to occur at higher frequency. MT1G and CRABP1 are novel genes that are likely involved in the pathogenesis of sporadic PTC.

p130 expression in thyroid neoplasms: its linkage with tumor size and dedifferentiation

p130 belongs to the retinoblastoma-related gene family, and its gene product works to negatively regulate cell cycle progression in the G1 phase. In this study, we investigated p130 expression in thyroid neoplasms. p130 overexpression was observed in 33.3% of follicular adenoma and 50% of follicular carcinoma and the incidences were not significantly different. In papillary carcinoma, it was overexpressed in 36.5% of cases, but in microcarcinoma, the incidence was significantly lower (14.3%). Furthermore, in anapalstic carcinoma, p130 overexpression was less frequently seen than in papillary carcinoma except for microcarcinoma and follicular carcinoma, and only 14.3% of cases overexpressed this protein. These findings suggest that: (1) reduced p130 expression may contribute to the aggressive character of anplastic carcinoma; and (2) p130 may specify the growth characteristics of microcarcinoma.

The phenotype of Hurthle and Warthin-like papillary thyroid carcinomas is distinct from classic papillary carcinoma as to the expression of retinoblastoma protein and E2F-1 transcription factor

Retinoblastoma protein plays an important role in controlling cell cycle progression. The active form of retinoblastoma protein binds to E2F-1 and inhibits transcription of S phase genes. Overexpression of E2F-1 has been suggested as an important factor in carcinogenesis. The Hurthle cell (HPCA) and Warthin-like (WLPCA) variants of papillary carcinoma are two closely related entities that arise in association with Hashimoto's thyroiditis and share the presence of oxyphilic changes in the lining of epithelial cells and the presence of papillary nuclear features. The current study included formalin-fixed, paraffin-embedded tissues from 58 cases of thyroid papillary carcinoma: 20 HPCA, 6 WLPCA, 22 conventional papillary carcinomas (PCA), and 10 follicular variants of papillary carcinoma (FVPCA). The immunohistochemical studies were performed for retinoblastoma (Rb-1) and E2F-1, (KH95) after heat-induced epitope retrieval. None of the PCA or FVPCA cases were in the positive range for Rb-1. All cases of HPCA and WLPCA of the thyroid showed reactivity in 50% or more of the nuclei in the neoplastic cell population. As for E2F-1, all cases of HPCA and WLPCA showed positive reactivity, whereas none of the PCA or FVPCA cases were in the positive range. In conclusion, HPCA and WLPCA are Rb-positive and E2F-1-positive; PCA and FVPCA are Rb-negative and E2F1-negative. Hurthle metaplastic epithelium in Hashimoto's thyroiditis is Rb-positive and E2F-1-negative. This phenotypic difference is also helpful in distinguishing hyperplastic Hurthle cell proliferation in Hashimoto's thyroiditis from HPCA or WLPCA.

Oxyphilic carcinoma of the thyroid gland

Oxyphilic tumors of the thyroid gland are rare tumors characterized by the presence of H?rthle cells - mitochondrion-rich, eosinophilic epithelial cells. H?rthle cell carcinomas (HCC) of the thyroid behave in a more aggressive fashion as compared to other well-differentiated thyroid cancers. Many recent studies have been focused on the further elucidation of pathogenesis and the role of mitochondrial hyperplasia in carcinogenesis of these neoplasms. The importance of combining morphological and genetic approaches in the study of HCC has been emphasized by the difficulties encountered in establishing adequate differential diagnostic criteria between benign and malignant forms, as well as by the resistance of HCC to radio and chemotherapy. It has been well documented that the H?rthle cells are characterized by profound aberrations in the nuclear and mitochondrial genome and by alterations in oncogenes, tumor suppressor genes and other key genes involved in energy metabolism, proliferation and apoptosis.

The meanings of markers: ancillary techniques in diagnosis of thyroid neoplasia

This review article primarily discusses immunohistochemical markers used to aid the diagnosis of thyroid neoplasia. The review concentrates on high molecular weight cytokeratins, cytokertain 19, HBME-1, and galectin-3. Diagnostic uses of proliferation markers such as p27(kip1) and Ki-67 are discussed along with the oncogene ret in relation to papillary carcinomas and PAX8-peroxisome proliferator-activated receptor gamma1 in relation to follicular carcinoma. The diagnostic use of retinoblastoma tumor suppressor gene product is also discussed. The sensitivities and specificities as well as the pitfalls of these techniques are reviewed. On the basis of the literature, the most highly recommended of these markers to aid in diagnosis are HBME-1 and galectin-3.