Histologic variants of papillary and follicular carcinomas associated with anaplastic spindle and giant cell carcinomas of the thyroid: an analysis of rhabdoid and thyroglobulin inclusions

WHO 2022 updates on follicular cell and c-cell derived thyroid neoplasm

The latest edition of the WHO Classification of thyroid tumors was released in 2022 and incorporates novel concepts vital to patient management. Thyroid follicular nodular disease is a term used to collectively represent a wide variety of benign and non-neoplastic lesions, including both clonal and non-clonal proliferations that manifest clinically as multinodular goiter. Thyroid neoplasms develop from follicular cells and can be either benign, low-risk, or malignant. To avoid classifying all lesions under 1 cm in diameter as low-risk illnesses, the new classification method highlights the need for subtyping papillary thyroid cancer based on histomorphologic indicators rather than tumor size. Formerly known as the cribriform-morular variety of papillary thyroid carcinoma, this tumor is now more commonly referred to by its more accurate name, cribriform-morular thyroid carcinoma. Its histogenesis is unknown. Similar to the traditional definition of 'poorly differentiated thyroid carcinoma' according to the Turin criteria, the newly defined 'differentiated high-grade thyroid carcinoma' encompasses papillary thyroid cancer, follicular thyroid carcinomas, and oncocytic carcinomas with high-grade characteristics linked to worse prognosis. The squamous cell subtype of anaplastic thyroid cancer has also recently been characterized as a distinct morphologic pattern. In this article, we will discuss the latest revision to the World Health Organization's classification system for thyroid cancer.

Glomangiosarcoma-like Anaplastic Transformation in Papillary Thyroid Carcinoma: A Novel Form of Heterologous Differentiation and a Systematic Review of Heterologous Element Prevalence

Anaplastic thyroid carcinoma (ATC) demonstrates a wide variety of morphologies and is characteristically associated with a differentiated thyroid carcinoma component. Heterologous differentiation is a rare, potentially challenging phenomenon in ATC, mostly observed as osteosarcomatous or chondrosarcomatous differentiation. We now describe a novel 'glomangiosarcoma-like' differentiation, review our archival experience from two institutions (UPMC, CC), and perform a systematic review for the prevalence of heterologous elements in ATC. The patient is a 57-year-old female who presented with 4.5 cm left thyroid, and 3.4 cm neck masses. Histologically, the thyroid demonstrated a differentiated high grade papillary thyroid carcinoma, tall cell and hobnail/micropapillary subtypes transitioning into an anaplastic component with spindled to ovoid cells with hemangiopericytoma-like vasculature showing CD34 positivity, variable muscle marker expression and pericellular lace-like type IV collagen deposition. The neck mass consisted solely of the latter morphology. Targeted next-generation sequencing was performed on high grade DTC and adjacent ATC from the thyroid as well as ATC from the neck metastasis. All three components shared BRAFV600E, TERT promoter, and PIK3CA mutations confirming a clonal origin. Archival (UPMC: n = 150, CC: n = 74) and literature review showed no prior examples. Systematic review and meta-analysis of prevalence showed a baseline pooled prevalence (generalized linear mixed model) of heterologous elements of any type to be 1.6% (95% confidence interval: 1.0-2.6%) for studies where this was specifically addressed. ATC with glomangiosarcoma-like heterologous differentiation is a rarity among an already rare morphologic category with unique diagnostic pitfalls.

Overview of the 2022 WHO Classification of Thyroid Neoplasms

This review summarizes the changes in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors that relate to the thyroid gland. The new classification has divided thyroid tumors into several new categories that allow for a clearer understanding of the cell of origin, pathologic features (cytopathology and histopathology), molecular classification, and biological behavior. Follicular cell-derived tumors constitute the majority of thyroid neoplasms. In this new classification, they are divided into benign, low-risk, and malignant neoplasms. Benign tumors include not only follicular adenoma but also variants of adenoma that are of diagnostic and clinical significance, including the ones with papillary architecture, which are often hyperfunctional and oncocytic adenomas. For the first time, there is a detailed account of the multifocal hyperplastic/neoplastic lesions that commonly occur in the clinical setting of multinodular goiter; the term thyroid follicular nodular disease (FND) achieved consensus as the best to describe this enigmatic entity. Low-risk follicular cell-derived neoplasms include non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), thyroid tumors of uncertain malignant potential, and hyalinizing trabecular tumor. Malignant follicular cell-derived neoplasms are stratified based on molecular profiles and aggressiveness. Papillary thyroid carcinomas (PTCs), with many morphological subtypes, represent the BRAF-like malignancies, whereas invasive encapsulated follicular variant PTC and follicular thyroid carcinoma represent the RAS-like malignancies. This new classification requires detailed subtyping of papillary microcarcinomas similar to their counterparts that exceed 1.0 cm and recommends not designating them as a subtype of PTC. The criteria of the tall cell subtype of PTC have been revisited. Cribriform-morular thyroid carcinoma is no longer classified as a subtype of PTC. The term "Hürthle cell" is discouraged, since it is a misnomer. Oncocytic carcinoma is discussed as a distinct entity with the clear recognition that it refers to oncocytic follicular cell-derived neoplasms (composed of > 75% oncocytic cells) that lack characteristic nuclear features of PTC (those would be oncocytic PTCs) and high-grade features (necrosis and ≥ 5 mitoses per 2 mm²). High-grade follicular cell-derived malignancies now include both the traditional poorly differentiated carcinoma as well as high-grade differentiated thyroid carcinomas, since both are characterized by increased mitotic activity and tumor necrosis without anaplastic histology and clinically behave in a similar manner. Anaplastic thyroid carcinoma remains the most undifferentiated form; squamous cell carcinoma of the thyroid is now considered as a subtype of anaplastic carcinoma. Medullary thyroid carcinomas derived from thyroid C cells retain their distinct section, and there is a separate section for mixed tumors composed of both C cells and any follicular cell-derived malignancy. A grading system for medullary thyroid carcinomas is also introduced based on mitotic count, tumor necrosis, and Ki67 labeling index. A number of unusual neoplasms that occur in the thyroid have been placed into new sections based on their cytogenesis. Mucoepidermoid carcinoma and secretory carcinoma of the salivary gland type are now included in one section classified as "salivary gland-type carcinomas of the thyroid." Thymomas, thymic carcinomas and spindle epithelial tumor with thymus-like elements are classified as "thymic tumors within the thyroid." There remain several tumors whose cell lineage is unclear, and they are listed as such; these include sclerosing mucoepidermoid carcinoma with eosinophilia and cribriform-morular thyroid carcinoma. Another important addition is thyroblastoma, an unusual embryonal tumor associated with DICER1 mutations. As in all the WHO books in the 5th edition, mesenchymal and stromal tumors, hematolymphoid neoplasms, germ cell tumors, and metastatic malignancies are discussed separately. The current classification also emphasizes the value of biomarkers that may aid diagnosis and provide prognostic information.

Cribriform-morular variant of papillary thyroid carcinoma with poorly differentiated features: report of a case and review of the literature

Introduction

Cribrifrom-morular variant of papillary thyroid carcinoma (CMVPTC) is an uncommon thyroid neoplasm that occurs predominantly in women and is sometime associated with familial adenomatous polyposis (FAP). Some of these tumors may undergo dedifferentiation to poorly differentiated thyroid carcinoma (PDTC). We describe a rare case of this carcinoma in a women without a history of FAP.

Case presentation

A 49-year-old woman with a history of breast carcinoma presented with a thyroid mass. A CMVPTC was diagnosed after excision. There was no history of FAP. Histological examination showed classical features of CMVPTC in most areas, but about 20% of the carcinoma showed features of a poorly differentiated carcinoma with a solid pattern of growth, increase mitotic activity and a high Ki-67 proliferative index (25%). Immunohistochemical stains were positive for nuclear and cytoplasmic beta catenin staining. These special studies supported the diagnosis.

Conclusion

CMVPTC with dedifferentiation to PDTC is a rare carcinoma with only 4 previous documented cases in the literature. This aggressive variant of thyroid carcinoma is more common in females, as is CMVPTC, and is often associated with an aggressive biological course. The cases usually express nuclear beta catenin and estrogen, progesterone and androgen receptors have been reported in some cases. Some cases may have somatic alterations of the APC gene and TERT promoter mutations. These carcinomas may metastasize to lung, bones and lymph nodes. Because of its aggressive behavior, patient with this diagnosis should be treated aggressively to control disease spread and mortality from the carcinoma.

Coexisting well-differentiated and anaplastic thyroid carcinoma in the same primary resection specimen: immunophenotypic and genetic comparison of the two components in a consecutive series of 13 cases and a review of the literature

Anaplastic carcinoma (AC) is a rare but highly aggressive form of thyroid cancer. It mostly arises on a background of pre-existing well-differentiated cancer (WDC); however, whether it evolves directly from a WDC or originates as a second independent neoplasm is still to be defined. To obtain further insights into these mechanisms, we performed morphological, immunohistochemical, and next-generation sequencing analyses to compare AC and its associated WDC in a subset of 13 surgically resected specimens. Histologically, most WDC were of aggressive subtypes. Papillary carcinomas (8 cases; 62%) were tall cell (4/8), columnar (1/8), classic with hobnail features (1/8), classic and follicular variant in the remaining 2 cases; Hürthle cell and follicular carcinomas were present in 5 (38%) and in 1 (8%) patient, respectively. One patient harbored both a PTC, follicular variant, and a Hürthle cell carcinoma. We did not find any correlation between a histotype of WDC and a specific anaplastic growth pattern. Immunohistochemically, ACs retained pankeratin/PAX8 expression but with significantly lower levels than WDCs, and they tended to lose TTF1 expression, as can be expected within a dedifferentiation process. In addition, AC showed a more frequent expression of p63 and/or SMA, a mutated pattern of p53, and an abnormal expression of p16. Genetic analysis showed that the number of mutations was higher in AC than in the associated WDC, confirming a role of the progressive accumulation of genetic damage in this transition. We observed that mutations found in the WDCs were consistently identified in the anaplastic counterparts, further supporting the hypothesis of a developmental link.

TMEM158 May Serve as a Diagnostic Biomarker for Anaplastic Thyroid Carcinoma: An Integrated Bioinformatic Analysis

Anaplastic thyroid carcinoma (ATC) is a rare but extremely lethal malignancy. However, little is known about the pathogenesis of ATC. Given its high mortality, it is critical to improve our understanding of ATC pathogenesis and to find new diagnostic biomarkers. In the present study, two gene microarray profiles (GSE53072 and GSE65144), which included 17 ATC and 17 adjacent non-tumorous tissues, were obtained. Bioinformatic analyses were then performed. Immunohistochemistry (IHC) and receiver operating characteristic (ROC) curves were then used to detect transmembrane protein 158 (TMEM158) expression and to assess diagnostic sensitivity. A total of 372 differentially expressed genes (DEGs) were identified. Through protein-protein interaction (PPI) analysis, we identified a significant module with 37 upregulated genes. Most of the genes in this module were related to cell-cycle processes. After co-expression analysis, 132 hub genes were selected for further study. Nine genes were identified as both DEGs and genes of interest in the weighted gene co-expression network analysis (WGCNA). IHC and ROC curves confirmed that TMEM158 was overexpressed in ATC tissue as compared with other types of thyroid cancer and normal tissue samples. We identified 8 KEGG pathways that were associated with high expression of TMEM158, including aminoacyl-tRNA biosynthesis and DNA replication. Our results suggest that TMEM158 may be a potential oncogene and serve as a diagnostic indicator for ATC.

SMARCB1 (INI1)-deficient thyroid carcinoma: A novel entity expanding the spectrum of tumors with INI1 loss

BACKGROUND

Biallelic loss of SMARCB1/INI1 is associated with highly aggressive malignancies, namely renal and extra-renal malignant rhabdoid tumors, and atypical teratoid/ rhabdoid tumor. Increasing availability of molecular testing and immunohistochemical stains acting as surrogate tools to genetic analysis has led to an increasing recognition of SMARCB1 loss in a variety of neoplasms. Interestingly, many of these lack the typical rhabdoid features ascribed to this group of tumors, making their identification difficult.

CASE PRESENTATION

We describe the cytological, histological, immunohistochemical and molecular features of the first case of primary SMARCB1 (INI1)-deficient carcinoma of the thyroid gland in literature. The tumor was unique in various aspects; apart from never having been documented at this location, it showed extensive glandular differentiation, mimicking metastatic adenocarcinoma.

CONCLUSION

Awareness of this novel entity is essential to avoid misdiagnosis, and for appropriate management, especially in an era of increased feasibility of targeted therapy.

Thyroid Tumors You Don't Want to Miss

This article examines more uncommon thyroid entities, including anaplastic thyroid carcinoma, poorly differentiated thyroid carcinoma, rare papillary thyroid carcinoma variants, medullary thyroid carcinoma, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), and multiple adenomatous nodules in the setting of Cowden syndrome. These entities were chosen based on their clinical significance and because they can be diagnostically challenging due to their morphologic diversity and overlap with other thyroid tumors. This article addresses the diagnostic features of each entity, focusing on how to avoid potential pitfalls and mimics while also highlighting the clinical implications of each diagnosis.

Mouse Model of Thyroid Cancer Progression and Dedifferentiation Driven by STRN-ALK Expression and Loss of p53: Evidence for the Existence of Two Types of Poorly Differentiated Carcinoma

Background: Thyroid tumor progression from well-differentiated cancer to poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) involves step-wise dedifferentiation associated with loss of iodine avidity and poor outcomes. ALK fusions, typically STRN-ALK, are found with higher incidence in human PDTC compared with well-differentiated cancer and, as previously shown, can drive the development of murine PDTC. The aim of this study was to evaluate thyroid cancer initiation and progression in mice with concomitant expression of STRN-ALK and inactivation of the tumor suppressor p53 (Trp53) in thyroid follicular cells. Methods: Transgenic mice with thyroid-specific expression of STRN-ALK and biallelic p53 loss were generated and aged on a regular diet or with methimazole and sodium perchlorate goitrogen treatment. Development and progression of thyroid tumors were monitored by using ultrasound imaging, followed by detailed histological and immunohistochemical evaluation. Gene expression analysis was performed on selected tumor samples by using RNA-Seq and quantitative RT-PCR. Results: In mice treated with goitrogen, the first thyroid cancers appeared at 6 months of age, reaching 86% penetrance by the age of 12 months, while a similar rate (71%) of tumor occurrence in mice on regular diet was observed by 18 months of age. Histological examination revealed well-differentiated papillary thyroid carcinomas (PTC) (n = 26), PDTC (n = 21), and ATC (n = 8) that frequently coexisted in the same thyroid gland. The tumors were frequently lethal and associated with the development of lung metastasis in 24% of cases. Histological and immunohistochemical characteristics of these cancers recapitulated tumors seen in humans. Detailed analysis of PDTC revealed two tumor types with distinct cell morphology and immunohistochemical characteristics, designated as PDTC type 1 (PDTC1) and type 2 (PDTC2). Gene expression analysis showed that PDTC1 tumors retained higher expression of thyroid differentiation genes including Tg and Slc5a5 (Nis) as compared with PDTC2 tumors. Conclusions: In this study, we generated a new mouse model of multistep thyroid cancer dedifferentiation with evidence of progression from PTC to PDTC and ATC. Further, PDTC in these mice showed two distinct histologic appearances correlated with levels of expression of thyroid differentiation and iodine metabolism genes, suggesting a possibility of existence of two PDTC types with different functional characteristics and potential implication for therapeutic approaches to these tumors.

Thyroid cancer stem-like cell exosomes: regulation of EMT via transfer of lncRNAs

Thyroid cancers are the most common endocrine malignancy and approximately 2% of thyroid cancers are anaplastic thyroid carcinoma (ATC), one of the most lethal and treatment resistant human cancers. Cancer stem-like cells (CSCs) may initiate tumorigenesis, induce resistance to chemotherapy and radiation therapy, have multipotent capability and may be responsible for recurrent and metastatic disease. The production of CSCs has been linked to epithelial-mesenchymal transition (EMT) and the acquisition of stemness. Exosomes are small (30-150 nm) membranous vesicles secreted by most cells that play a significant role in cell-to-cell communication. Many non-coding RNAs (ncRNA), such as long-non-coding RNAs (lncRNA), can initiate tumorigenesis and the EMT process. Exosomes carry ncRNAs to local and distant cell populations. This study examines secreted exosomes from two in vitro cell culture models; an EMT model and a CSC model. The EMT was induced in a papillary thyroid carcinoma (PTC) cell line by TGFβ1 treatment. Exosomes from this model were isolated and cultured with naïve PTC cells and examined for EMT induction. In the CSC model, exosomes were isolated from a CSC clonal line, cultured with a normal thyroid cell line and examined for EMT induction. The EMT exosomes transferred the lncRNA MALAT1 and EMT effectors SLUG and SOX2; however, EMT was not induced in this model. The exosomes from the CSC model also transferred the lncRNA MALAT1 and the transcription factors SLUG and SOX2 but additionally transferred linc-ROR and induced EMT in the normal thyroid cells. Preliminary siRNA studies directed towards linc-ROR reduced invasion. We hypothesize that CSC exosomes transfer lncRNAs, importantly linc-ROR, to induce EMT and inculcate the local tumor microenvironment and the distant metastatic niche. Therapies directed towards CSCs, their exosomes and/or the lncRNAs they carry may reduce a tumor's metastatic capacity.

Special types of thyroid carcinoma

This article reviews the small percentage of thyroid tumours that are not classified as classic papillary thyroid carcinoma, follicular thyroid carcinoma, and medullary thyroid carcinoma. It includes subtypes of papillary thyroid carcinoma, including, tall-cell, hobnail/micropapillary, columnar cell, diffuse sclerosing and solid variants. Poorly differentiated carcinoma, high-grade carcinoma and anaplastic thyroid carcinoma are reviewed. Also discussed are entities that are unusual but need to be recognized as primary thyroid neoplasms, i.e. mucoepidermoid carcinoma, sclerosing mucoepidermoid carcinoma with eosinophilia, and mammary analogue secretory carcinoma/secretory carcinoma. The pathological features and prognostic factors are described; a brief review of molecular correlates of these neoplasms is included.

Anaplastic thyroid carcinoma: an epidemiologic, histologic, immunohistochemical, and molecular single-institution study

Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of thyroid cancer. A single-institution thyroid cancer cohort of ATC was identified within the last 10 years at our institution. Retrospective analysis revealed that the frequency of ATC was 0.5% (11/2106 thyroid carcinomas). The average age at diagnosis of ATC was 74 years, and the female-to-male ratio was 1.2:1. ATC presented as a rapidly enlarging neck mass involving predominantly the left thyroid lobe (7/11; 64%). Cervical adenopathy was present in 7 (64%) of 11 cases. Fifty-five percent (6/11) of patients had distant metastases at the time of diagnosis. Histologically, ATC closely simulated a large variety of soft tissue sarcomas; osteoclast-like giant cell-rich tumors; squamous cell, spindle cell, and small cell carcinomas; and anaplastic/large cell lymphomas. Four tumors (4/11; 36%) showed heterologous elements, including rhabdoid and chondroid differentiation. Immunohistochemical studies showed that all ATCs lost TTF-1 and thyroglobulin expression, whereas PAX-8 expression was identified in 36% (4/11) of tumors. Intense and extensive nuclear staining of p53 (>50%) and high Ki-67 proliferative rate (>30%) were seen in all ATCs (11/11; 100%). Next-generation sequencing revealed recurrent BRAF V600E and TP53 gene mutations. Individual examples of a BRAF G469A mutation in ATC with follicular carcinoma component, EGFR, PTEN, PIK3CA, and FGFR3 mutations, were also identified, whereas 1 case of ATC showed wild-type sequencing with no identifiable alterations.

Anaplastic thyroid carcinoma: from clinicopathology to genetics and advanced therapies

Anaplastic thyroid carcinoma (ATC) is a rare malignancy, accounting for 1-2% of all thyroid cancers. Although rare, ATC accounts for the majority of deaths from thyroid carcinoma. ATC often originates in a pre-existing thyroid cancer lesion, as suggested by the simultaneous presence of areas of differentiated or poorly differentiated thyroid carcinoma. ATC is characterized by the accumulation of several oncogenic alterations, and studies have shown that an increased number of oncogenic alterations equates to an increased level of dedifferentiation and aggressiveness. The clinical management of ATC requires a multidisciplinary approach; according to recent American Thyroid Association guidelines, surgery, radiotherapy and/or chemotherapy should be considered. In addition to conventional therapies, novel molecular targeted therapies are the most promising emerging treatment modalities. These drugs are often multiple receptor tyrosine kinase inhibitors, several of which have been tested in clinical trials with encouraging results so far. Accordingly, clinical trials are ongoing to evaluate the safety, efficacy and effectiveness of these new agents. This Review describes the updated clinical and pathological features of ATC and provides insight into the molecular biology of this disease. The most recent literature regarding conventional, newly available and future therapies for ATC is also discussed.

Histopathological analysis of anaplastic thyroid carcinoma cases with long-term survival: A report from the Anaplastic Thyroid Carcinoma Research Consortium of Japan

The aim of this study was to clarify the histopathological features of anaplastic thyroid carcinoma in patients who achieved long-term survival. We reviewed 88 anaplastic thyroid carcinoma cases in which the patient survived less than 3 months (short-term survival), and 68 anaplastic thyroid carcinoma cases in which the patient survived more than one year (long-term survival) from the database of the Anaplastic Thyroid Carcinoma Research Consortium of Japan. We examined these cases both histologically and immunohistochemically. Six (6.8%) short-term survival cases and 27 (39.7%) long-term survival cases were considered not to be anaplastic thyroid carcinoma after central review. Of these, 12 were revised to papillary carcinoma with squamous cell carcinoma. In cases without chemotherapy, long-term survival was significantly more common if there was a pre-existing tumor, epithelial growth, or lymphocytic infiltration, and short-term survival was more common if neutrophilic infiltration was present. In cases with chemotherapy, long-term survival was significantly more common if epithelial growth or a squamous cell carcinoma component was present, whereas short-term survival was more common in cases with rhabdoid cells. Immunohistochemical results were not related to survival. Some long-term survival cases showed histological findings other than those typically associated with anaplastic thyroid carcinoma. The presence of a pre-existing tumor, epithelial growth, a squamous cell carcinoma component, no neutrophilic infiltration and lymphocytic infiltration may therefore be favorable prognostic factors in anaplastic thyroid carcinoma.

Informed consent for low-risk thyroid cancer

Significant barriers to informed consent surround the clinical management of adult patients with well-differentiated thyroid cancer. The literature reveals lack of disclosure surrounding clinical equipoise; confusing and conflicting terminology; and an insufficient number of prospective trials with proper ethical oversight. We provide guidance for valid consent to treatment in this population, and propose stipulative definitions for a variety of terms used in this context. Three critical areas are addressed: surgical management, radioactive iodine management and nonvalidated practice. Sound ethical frameworks for valid consent in patients with low-risk thyroid cancer include consent to observational (or ‘active surveillance’) research protocols, consent to nonvalidated practice and consent when there are opposing standards of care due to insufficient data and disagreement among the community of experts.

Generation of Novel Thyroid Cancer Stem-Like Cell Clones: Effects of Resveratrol and Valproic Acid

Anaplastic thyroid cancer is an aggressive and highly lethal cancer for which conventional therapies have proved ineffective. Cancer stem-like cells (CSCs) represent a small fraction of cells in the cancer that are resistant to chemotherapy and radiation therapy and are responsible for tumor reoccurrence and metastasis. We characterized CSCs in thyroid carcinomas and generated clones of CSC lines. Our study showed that anaplastic thyroid cancers had significantly more CSCs than well-differentiated thyroid cancers. We also showed that Aldefluor-positive cells revealed significantly higher expression of stem cell markers, self-renewal properties, thyrosphere formation, and enhanced tumorigenicity. In vivo passaging of Aldefluor-positive cells resulted in the growth of larger, more aggressive tumors. We isolated and generated two clonal spheroid CSC lines derived from anaplastic thyroid cancer that were even more enriched with stem cell markers and more tumorigenic than the freshly isolated Aldefluor-positive cells. Resveratrol and valproic acid treatment of one of the CSC lines resulted in a significant decrease in stem cell markers, Aldefluor expression, proliferation, and invasiveness, with an increase in apoptosis and thyroid differentiation markers, suggesting that these cell lines may be useful for discovering new adjuvant therapies for aggressive thyroid cancers. For the first time, we have two thyroid CSC lines that will be useful tools for the study of thyroid CSC targeted therapies.

Rhabdomyoblastic Differentiation in Head and Neck Malignancies Other Than Rhabdomyosarcoma

Rhabdomyosarcoma is a relatively common soft tissue sarcoma that frequently affects children and adolescents and may involve the head and neck. Rhabdomyosarcoma is defined by skeletal muscle differentiation which can be suggested by routine histology and confirmed by immunohistochemistry for the skeletal muscle-specific markers myogenin or myoD1. At the same time, it must be remembered that when it comes to head and neck malignancies, skeletal muscle differentiation is not limited to rhabdomyosarcoma. A lack of awareness of this phenomenon could lead to misdiagnosis and, subsequently, inappropriate therapeutic interventions. This review focuses on malignant neoplasms of the head and neck other than rhabdomyosarcoma that may exhibit rhabdomyoblastic differentiation, with an emphasis on strategies to resolve the diagnostic dilemmas these tumors may present. Axiomatically, no primary central nervous system tumors will be discussed.

Cancer stem-like cells and thyroid cancer

Thyroid cancer is one of the most rapidly increasing malignancies. The reasons for this increase is not completely known, but increases in the diagnosis of papillary thyroid microcarcinomas and follicular variant of papillary thyroid carcinomas along with the enhanced detection of well-differentiated thyroid carcinomas are probably all contributing factors. Although most cases of well-differentiated thyroid carcinomas are associated with an excellent prognosis, a small percentage of patients with well-differentiated thyroid carcinomas as well as most patients with poorly differentiated and anaplastic thyroid carcinomas have recurrent and/or metastatic disease that is often fatal. The cancer stem-like cell (CSC) model suggests that a small number of cells within a cancer, known as CSCs, are responsible for resistance to chemotherapy and radiation therapy, as well as for recurrent and metastatic disease. This review discusses current studies about thyroid CSCs, the processes of epithelial-to-mesenchymal transition (EMT), and mesenchymal-to-epithelial transition that provide plasticity to CSC growth, in addition to the role of microRNAs in CSC development and regulation. Understanding the biology of CSCs, EMT and the metastatic cascade should lead to the design of more rational targeted therapies for highly aggressive and fatal thyroid cancers.

The roles of the epithelial-mesenchymal transition marker PRRX1 and miR-146b-5p in papillary thyroid carcinoma progression

Thyroid carcinoma is the most common endocrine malignancy, and papillary thyroid carcinoma represents the most common thyroid cancer. Papillary thyroid carcinomas that invade locally or metastasize are associated with a poor prognosis. We found that, during epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1), papillary thyroid carcinoma cells acquired increased cancer stem cell-like features and the transcription factor paired-related homeobox protein 1 (PRRX1; alias PRX-1), a newly identified EMT inducer, was markedly up-regulated. miR-146b-5p was also transiently up-regulated during EMT, and in siRNA experiments miR-146b-5p had an inhibitory role on cell proliferation and invasion during TGF-β1-induced EMT. We conclude that papillary thyroid carcinoma tumor cells exhibit increased cancer stem cell-like features during TGF-β1-induced EMT, that miR-146b-5p has a role in cell proliferation and invasion, and that PRRX1 plays an important role in papillary thyroid carcinoma EMT and disease progression.

Thyroid tumor-initiating cells: increasing evidence and opportunities for anticancer therapy (review)

Accumulating evidence supports the notion that thyroid cancer is initiated by tumor-initiating cells (TICs) (commonly known as cancer stem cells), which are thought to play a crucial role in malignant progression, therapeutic resistance and recurrence. Thyroid TICs have been isolated and identified using specific biomarkers (such as CD133), the side population, sphere formation and aldehyde dehydrogenase activity assays. Although their characteristics remain largely unknown, TICs provide an attractive cellular mechanism to explain therapeutic refractoriness. Efforts are currently being directed toward the identification of therapeutic strategies that could target these cells. The present review discusses the cellular origins of TICs and the main approaches used to isolate and identify thyroid TICs, with a focus on the remaining challenges and opportunities for anticancer therapy.

PAX8 is expressed in anaplastic thyroid carcinoma diagnosed by fine-needle aspiration: a study of three cases with histological correlates

OBJECTIVE

It is difficult to diagnose anaplastic thyroid carcinoma (ATC) in a fine-needle aspiration (FNA) sample because, given the loss of morphological and immunophenotypical follicular thyroid features, its cytology resembles that of other undifferentiated neoplasms. Recent studies have shown that immunostaining for paired box gene 8 (PAX8), a transcription factor expressed in normal thyroid, is effective for diagnosing ATCs on histology. The aim of this study was to evaluate whether PAX8 could be used to identify ATCs on cytology also.

DESIGN AND METHODS

We selected three PAX8-immunostained undifferentiated FNA samples previously diagnosed as suspected ATCs, whose cell block had been negative for the expression of TGB and thyroid transcription factor-1. Matched histological samples, available in two cases, were also processed for PAX8 immunohistochemistry.

RESULTS

All three FNA samples were PAX8 positive. Two samples that had an epithelioid pattern showed a diffuse, intense nuclear signal. The third sample, which had a spindle-cell pattern, showed less intense and more patchy staining. Matched histology yielded overlapping results.

CONCLUSIONS

PAX8 immunocytochemistry can help cytopathologists to diagnose ATCs.

Stem cells and cancer stem-like cells in endocrine tissues

Cancer stem-like cells are a subpopulation of self-renewing cells that are more resistant to chemotherapy and radiation therapy than the other surrounding cancer cells. The cancer stem cell model predicts that only a subset of cancer cells possess the ability to self-renew and produce progenitor cells that can reconstitute and sustain tumor growth. Evidence supporting the existence of cancer stem-like cells in the thyroid, pituitary, and in other endocrine tissues is rapidly accumulating. These cells have been studied using specific biomarkers including: CD133, CD44, Nestin, Nanog, and aldehyde dehydrogenase enzyme. Putative cancer stem-like cells can be studied in vitro using serum-free media supplemented with basic fibroblast growth factor and epidermal growth factor grown in low attachment plates or in extracellular matrix leading to sphere formation in vitro. Cancer stem-like cells can also be separated by fluorescent cell sorting and used for in vitro or in vivo studies. Injection of enriched populations of cancer stem-like cells (also referred to as tumor initiating cells) into immunodeficient mice results in growth of xenografts which express cancer stem-like biomarkers. Human cancer stem-like cells have been identified in thyroid cancer cell lines, in primary thyroid cancers, in normal pituitary, and in pituitary tumors. Other recent studies suggest the existence of stem cells and cancer stem-like cells in endocrine tumors of the gastrointestinal tract, pancreas, lungs, adrenal, parathyroid, and skin. New discoveries in this field may lead to more effective therapies for highly aggressive and lethal endocrine cancers.

American Thyroid Association guidelines for management of patients with anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is a rare but highly lethal form of thyroid cancer. Rapid evaluation and establishment of treatment goals are imperative for optimum patient management and require a multidisciplinary team approach. Here we present guidelines for the management of ATC. The development of these guidelines was supported by the American Thyroid Association (ATA), which requested the authors, members the ATA Taskforce for ATC, to independently develop guidelines for ATC.

METHODS

Relevant literature was reviewed, including serial PubMed searches supplemented with additional articles. The quality and strength of recommendations were adapted from the Clinical Guidelines Committee of the American College of Physicians, which in turn was developed by the Grading of Recommendations Assessment, Development and Evaluation workshop.

RESULTS

The guidelines include the diagnosis, initial evaluation, establishment of treatment goals, approaches to locoregional disease (surgery, radiotherapy, systemic therapy, supportive care during active therapy), approaches to advanced/metastatic disease, palliative care options, surveillance and long-term monitoring, and ethical issues including end of life. The guidelines include 65 recommendations.

CONCLUSIONS

These are the first comprehensive guidelines for ATC and provide recommendations for management of this extremely aggressive malignancy. Patients with stage IVA/IVB resectable disease have the best prognosis, particularly if a multimodal approach (surgery, radiation, systemic therapy) is used, and some stage IVB unresectable patients may respond to aggressive therapy. Patients with stage IVC disease should be considered for a clinical trial or hospice/palliative care, depending upon their preference.

Papillary thyroid carcinoma variants

Papillary thyroid carcinomas are the most common thyroid cancers and constitute more than 70% of thyroid malignancies. The most common etiologic factor is radiation, but genetic susceptibility and other factors also contribute to the development of papillary thyroid carcinoma. The most common variants include conventional, follicular variant and tall cell variant. However, many other uncommon variants have been described including oncocytic, columnar cell, diffuse sclerosing and solid forms. Immunohistochemical staining with TTF-1 and thyroglobulin is very useful in confirming the diagnosis of papillary thyroid carcinoma especially in metastatic sites. Markers such as HBME-1 and CITED1 can assist in separating some difficult cases of follicular variants of papillary thyroid carcinomas from follicular adenomas. Molecular studies have shown that the BRAF V600E mutation is found mainly in papillary and anaplastic thyroid carcinomas. Other molecular markers such as HMGA2 and insulin-like growth factor II mRNA binding protein 3 have been used recently as molecular tests to separate papillary thyroid carcinoma and its variants from follicular adenomas and other benign thyroid nodules.

Unusual metastases of papillary thyroid carcinoma: report of 2 cases

We present 2 cases of papillary thyroid carcinoma (PTC) with conventional morphology that metastasized to unusual sites. The first neoplasm was a PTC whose initial clinical manifestation was a large metastasis in the pancreas which mimicked a primary neoplasm. The mediastinal location of the thyroid gland was responsible for the delay in identification of the primary tumor. Eventually, the patient, a 72-year-old man, developed brain and vertebral metastases. The second case was that of a 58-year-old woman with a PTC with initial metastases in cervical lymph nodes; subsequently, the tumor spread to axillary lymph nodes and finally to the breast. Transformation to anaplastic spindle and giant cell carcinoma within the breast metastasis occurred 20 years after the primary thyroid tumor had been diagnosed and surgically treated. The metastatic anaplastic spindle and giant cell carcinoma contained rhabdoid inclusions further complicating identification. To the best of our knowledge, only 3 cases of PTC metastatic to the breast have been reported, none of them with anaplastic transformation. On the other hand, only 3 cases of PTC metastatic to the pancreas have been published, 2 of them of the tall cell variant, and in none of these cases were the first symptoms attributable to the metastasis. Brief comments about the differential diagnosis are included.

Anaplastic thyroid carcinoma with rhabdomyoblastic differentiation: a case report with a good clinical outcome

Anaplastic thyroid carcinoma is a rare and highly malignant disease. Usually, this type of tumor is irresectable, and almost all patients die within 1 year after diagnosis. We present a case of anaplastic thyroid carcinoma with rhabdomyoblastic differentiation and good therapeutic outcome. A 76-year-old female was referred to our hospital with a growing, painless neck mass which existed for 3 months. Biopsy of the mass showed microscopically and immunohistochemically a follicular (Hürthle cell) carcinoma of the thyroid, dedifferentiated to an anaplastic carcinoma with divergent differentiation along rhabdomyoblastic cell lines. The patient underwent a total thyroidectomy with additional lymph node dissection, followed by two episodes of 150 mC I(131) therapy and external radiotherapy. After a follow-up of 3 years, the patient still remains in a good condition without any signs of recurrent disease. Other cases of rhabdomyoblastic and rhabdoid anaplastic thyroid carcinomas have been described. Both types of carcinoma are associated with an aggressive clinical course. In our case, the patient is still alive without evidence of disease 3 years after primary therapy. The good clinical outcome of our patient suggests that surgical resection, radiotherapy, and I-131 ablation therapy with curative intent seems to be an adequate treatment option in patients with anaplastic thyroid carcinoma with rhabdoid and rhabdomyoblastic differentiation.

Changing patterns in the incidence and survival of thyroid cancer with follicular phenotype--papillary, follicular, and anaplastic: a morphological and epidemiological study

Thyroid carcinomas with follicular phenotype have demonstrated changing patterns over 30 years (1973-2003) according to data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Papillary carcinomas have significantly increased. They accounted for 74% of all cases of thyroid cancers in 1973 and 87% in 2003. During this period, the incidence rate of papillary carcinoma (including the follicular variant) increased by 189%, the rate of follicular carcinoma remained stable, and the rate of anaplastic carcinoma decreased by 22%. The rate of the follicular variant of papillary carcinoma alone increased by 173%. Thyroid cancer was more common in whites than in blacks and in females more than in males. Papillary carcinomas rapidly increased during adolescence and reached a peak around age 52-56, then declined. Follicular carcinomas increased steadily, but at a lower rate until age 80. After 1988, both papillary and follicular carcinomas, less than 2 cm, increased at the same rate as carcinomas larger than 2 cm. However, papillary carcinomas less than 2 cm were more common. Overall, the 10-year relative survival rate was greater than 90% for blacks and whites with the exception of follicular carcinoma in blacks. The 10-year relative survival rate for anaplastic carcinoma in patients over 40 years of age was 4.7%. The decrease in incidence rate of anaplastic carcinoma may be the result of the successful treatment of papillary and follicular carcinomas.