EWSR1 rearrangement is a frequent event in papillary thyroid carcinoma and in carcinoma of the thyroid with Ewing family tumor elements (CEFTE)

Genetic alterations landscape in paediatric thyroid tumours and/or differentiated thyroid cancer: Systematic review

Differentiated thyroid cancer (DTC) is a rare disease in the paediatric population (≤ 18 years old. at diagnosis). Increasing incidence is reflected by increases in incidence for papillary thyroid carcinoma (PTC) subtypes. Compared to those of adults, despite aggressive presentation, paediatric DTC has an excellent prognosis. As for adult DTC, European and American guidelines recommend individualised management, based on the differences in clinical presentation and genetic findings. Therefore, we conducted a systematic review to identify the epidemiological landscape of all genetic alterations so far investigated in paediatric populations at diagnosis affected by thyroid tumours and/or DTC that have improved and/or informed preventive and/or curative diagnostic and prognostic clinical conduct globally. Fusions involving the gene RET followed by NTRK, ALK and BRAF, were the most prevalent rearrangements found in paediatric PTC. BRAF V600E was found at lower prevalence in paediatric (especially ≤ 10 years old) than in adults PTC. We identified TERT and RAS mutations at very low prevalence in most countries. DICER1 SNVs, while found at higher prevalence in few countries, they were found in both benign and DTC. Although the precise role of DICER1 is not fully understood, it has been hypothesised that additional genetic alterations, similar to that observed for RAS gene, might be required for the malignant transformation of these nodules. Regarding aggressiveness, fusion oncogenes may have a higher growth impact compared with BRAF V600E. We reported the shortcomings of the systematized research and outlined three key recommendations for global authors to improve and inform precision health approaches, glocally.

Transcriptomic and immunophenotypic characterization of two cases of adamantinoma-like Ewing sarcoma of the thyroid gland

INTRODUCTION

Adamantinoma-like Ewing sarcoma (ALES) is a rare aggressive malignancy occasionally diagnosed in the thyroid gland. ALES shows basaloid cytomorphology, expresses keratins, p63, p40, frequently CD99, and harbours the t(11;22) EWSR1::FLI1 translocation. There is debate on whether ALES resembles more sarcoma or carcinoma.

METHODS

We performed RNA sequencing from two ALES cases and compared findings with skeletal Ewing's sarcomas and nonneoplastic thyroid tissue. ALES was investigated by in situ hybridization (ISH) for high-risk human papillomavirus (HPV) DNA and immunohistochemistry for the following antigens: keratin 7, keratin 20, keratin 5, keratins (AE1/AE3 and CAM5.2), CD45, CD20, CD5, CD99, chromogranin, synaptophysin, calcitonin, thyroglobulin, PAX8, TTF1, S100, p40, p63, p16, NUT, desmin, ER, FLI1, INI1, and myogenin.

RESULTS

An uncommon EWSR1::FLI transcript with retained EWSR1 exon 8 was detected in both ALES cases. Regulators of EWSR1::FLI1 splicing (HNRNPH1, SUPT6H, SF3B1) necessary for production of a functional fusion oncoprotein, as well as 53 genes (including TNNT1, NKX2.2) activated downstream to the EWSR1::FLI1 cascade, were overexpressed. Eighty-six genes were uniquely overexpressed in ALES, most of which were related to squamous differentiation. Immunohistochemically, ALES strongly expressed keratins 5, AE1/AE3 and CAM5.2, p63, p40, p16, and focally CD99. INI1 was retained. The remaining immunostains and HPV DNA ISH were negative.

CONCLUSION

Comparative transcriptomic profiling reveals overlapping features of ALES with skeletal Ewing's sarcoma and an epithelial carcinoma, as evidenced by immunohistochemical expression of keratin 5, p63, p40, CD99, the transcriptome profile, and detection of EWSR1::FLI1 fusion transcript by RNA sequencing.

Adamantinoma-like Ewing sarcoma of the salivary glands: a case report and systematic literature review

Adamantinoma-like Ewing sarcoma (ALES) of the salivary glands is an exceedingly rare malignancy defined by the t(11,22) EWSR1::FLI1 fusion, with complex epithelial differentiation. To identify features that can allow for better recognition of this disease entity, we reviewed all published reports of molecularly confirmed ALES of the salivary glands and explored epidemiological, clinical, radiological, pathological, and therapeutic characteristics of a population of 21 patients including a single newly reported patient from our group. We searched the English-language literature indexed in PubMed, Medline, Scopus, and Web of Science using the keyword 'Adamantinoma-like Ewing sarcoma' published up to June 2022. The median age at diagnosis was 46 years, and a slight female sex predilection was observed. Most tumors originated in the parotid gland (86%) and presented as a painless palpable mass with a median diameter of 3.6 cm. Metastatic dissemination was reported only in one patient (5%), and after a median follow-up of 13 months the 1-year overall survival rate was 92%. Salivary gland ALES were frequently misdiagnosed at presentation (62% of cases) and were pathologically characterized by the presence of highly monomorphic small round blue cells with infiltrative pattern and positive immunostaining for CD99 and high- and low-molecular weight cytokeratins. Epidemiological and clinical features of salivary gland ALES raise questions on the incorporation of this malignancy in the Ewing sarcoma family tumor group.

Proceedings of the North American Society of Head and Neck Pathology, Los Angeles, CA, March 20, 2022. Emerging Bone and Soft Tissue Neoplasms in the Head and Neck Region

In the past decade, several emerging bone and soft tissue neoplasms of the head and neck region have been described in the literature, including GLI1-altered mesenchymal tumors, (intraosseous) rhabdomyosarcoma with TFCP2 fusion, and adamantinoma-like Ewing sarcoma. This review provides a summary of the clinical features, histologic characteristics, immunoprofile, key diagnostic features, and differential diagnoses of these emerging entities. Notably, all three entities show epithelioid morphology and cytokeratin immunopositivity, highlighting the need to consider these mesenchymal neoplasms in the differential diagnoses of cytokeratin-positive epithelioid tumors in the head and neck region. Appropriate workups including detection of the characteristic molecular alterations are essential for the correct diagnosis.

Primary Extra-Osseous Ewing Sarcoma of the Thyroid: A Case Report and Review of the Literature

Extra-osseous Ewing sarcoma (ES) is a rare and aggressive malignant tumor found in a variety of organs. Primary ES of the thyroid is exceedingly rare and few cases have been documented to date. We describe the case of a 54-year old woman with a history of breast carcinoma in whom a unique hypermetabolic left thyroid nodule was identified during a follow-up PET-CT scan. An ultrasound examination showed a hypoechogenic nodule of 3.7 cm. A cytological diagnosis of poorly differentiated thyroid carcinoma was made, and a total thyroidectomy was performed. The surgical specimen revealed a poorly differentiated neoplasm composed of medium-sized cells with scant cytoplasm, expressing pancytokeratin, CD99 and NKX2.2 but lacking p63 and p40 expression. Molecular analysis revealed a EWSR1-FLI1 fusion transcript supporting the diagnosis of a primary extra-osseous ES of the thyroid. The patient received adjuvant chemotherapy and has no evidence of recurrent disease.

Molecular Pathology of Non-familial Follicular Epithelial-Derived Thyroid Cancer in Adults: From RAS/BRAF-like Tumor Designations to Molecular Risk Stratification

This review addresses the impact of molecular alterations on the diagnosis and prognosis of differentiated thyroid carcinoma (DTC), including papillary, follicular, and well-differentiated carcinoma NOS, as well as oncocytic neoplasms. The molecular characterization of DTC is based upon the well-established dichotomy of BRAF-like and RAS-like designations, together with a remaining third group, less homogeneous, composed of non-BRAF-/non-RAS-like tumors. The role of BRAF V600E mutation in risk stratification is discussed in the clinico-pathological context, namely, staging and invasive features of classic papillary thyroid carcinoma (PTC) and histopathological variants carrying an excellent prognosis (microPTC) or a guarded prognosis, including the aggressive variants tall cell and hobnail cell PTCs. In follicular patterned tumors, namely, follicular thyroid carcinoma (FTC), with or without oncocytic features, the most prevalent molecular alteration are RAS mutations that do not carry prognostic significance. The only genetic alteration that has been proven to play a role in risk stratification of PTC and FTC is TERT promoter (TERTp) mutation.

Pitfalls in Challenging Thyroid Tumors: Emphasis on Differential Diagnosis and Ancillary Biomarkers

Thyroid pathology encompasses a heterogenous group of clinicopathological entities including rare and diagnostically challenging neoplasms. The review is focused on morphological, immunohistochemical, and molecular features of rare thyroid neoplasms that can pose diagnostic problems. The tumors are organized based on growth patterns including thyroid neoplasms with predominantly papillary, follicular, solid, and spindle cell growth pattern, as well as neoplasms with distinct cytological characteristics. A special section is also dedicated to rare thyroid tumors with peculiar patterns including thyroid carcinoma with Ewing family tumor elements and intrathyroidal thymic-related neoplasms.

Carcinomas of the Thyroid with Ewing Family Tumor Elements (CEFTEs): A Diagnostic Challenge Before Surgery

Carcinomas of the thyroid with Ewing family tumor elements (CEFTEs) are small cell thyroid tumors characterized by epithelial differentiation and EWSR1-FLI1 rearrangements. In contrast to primary thyroid Ewing sarcomas, these rare tumors have a favorable prognosis. CEFTEs may co-exist with papillary thyroid carcinoma (PTC) foci and are thought to arise from either PTCs or main cells of solid cell nests (SCN). Due to their rare occurrence, characteristic clinical presentations, preoperatory sonographic (US) findings, and fine-needle aspiration (FNA) cytologic features were ill-defined until now. We report a case of a 40-year-old male who was referred to the thyroid clinic for a progressively enlarging, hard, painless, cervical mass. US examination revealed a hypoechoic nodule with lobulated margins and scant intranodular vascular signals of the right thyroid lobe. Evidence of extracapsular spread was not identified. FNA provided a Bethesda V cytology classification on conventional smears. Repeat FNA sampling with the use of a CytoFoam Core allowed a preoperative diagnosis consistent with undifferentiated thyroid carcinoma. Total thyroidectomy without lymph node dissection was performed. Histologic examination with subsequent molecular studies provided the diagnosis of papillary carcinoma of the thyroid with Ewing family tumour elements (CEFTEs). No additional treatment was rendered and the patient showed no evidence of local or distant disease by clinical examination, US, and ¹⁸FDG-TAC/PET after 6 months of follow-up. This is the first reported case of CEFTE with complete clinical, US, cytologic, and immunohistochemical preoperatory assessment.

Adamantinoma-like Ewing Sarcoma of the Salivary Glands: A Newly Recognized Mimicker of Basaloid Salivary Carcinomas

Adamantinoma-like Ewing sarcoma (ALES) is a rare tumor that demonstrates the EWSR1-FLI1 translocation characteristic of Ewing sarcoma despite overt epithelial differentiation including diffuse expression of cytokeratins and p40. Most cases of ALES described to date have occurred in the head and neck where they can mimic a wide range of small round blue cell tumors. Because distinguishing ALES from basaloid salivary gland carcinomas can be particularly difficult, we analyzed a series of 10 ALESs that occurred in the salivary glands with the aim of identifying features that allow for better recognition of this entity. The salivary ALESs included 8 parotid gland and 2 submandibular gland tumors in patients ranging from 32 to 77 years (mean: 52 y). Nine were initially misclassified as various epithelial neoplasms. Although these tumors displayed the basaloid cytology, rosette formation, infiltrative growth, and nuclear monotony characteristic of ALES, peripheral palisading and overt keratinization were relatively rare in this site. Salivary ALESs not only displayed positivity for AE1/AE3, p40, and CD99, but also demonstrated a higher proportion of synaptophysin reactivity than has been reported for nonsalivary ALESs. These morphologic and immunohistochemical findings make ALES susceptible to misclassification as various other tumors including basal cell adenocarcinoma, adenoid cystic carcinoma, squamous cell carcinoma, NUT carcinoma, large cell neuroendocrine carcinoma and myoepithelial carcinoma. Nevertheless, monotonous cytology despite highly infiltrative growth and concomitant positivity for p40 and synaptophysin can provide important clues for consideration of ALES, and identification of the defining EWSR1-FLI1 translocations can confirm the diagnosis.

Fifty years of thyroid pathology: concepts and developments

The past half century has seen a number of advances in pathology of thyroid diseases, especially neoplastic lesions. These include the description of new entities, the definition of prognostically important lesions, the incorporation of fine needle aspiration biopsy and its functional risk stratification of diagnoses into the clinical evaluation and therapeutic recommendations of the patient with thyroid nodules and the understanding of thyroid neoplastic development, diagnostic and prognostic parameters by use of molecular analysis so that such techniques are becoming standard of care for patients with thyroid tumors. The histopathologist and cytopathologist have been and continue to be at the forefront in the definition and understanding of these areas of thyroid disease. This review describes many of the most important advances in this area in an attempt bring the practicing pathologist up to date in these developments.

The Immune Landscape of Thyroid Cancer in the Context of Immune Checkpoint Inhibition

Immune cells play critical roles in tumor prevention as well as initiation and progression. However, immune-resistant cancer cells can evade the immune system and proceed to form tumors. The normal microenvironment (immune cells, fibroblasts, blood and lymphatic vessels, and interstitial extracellular matrix (ECM)) maintains tissue homeostasis and prevents tumor initiation. Inflammatory mediators, reactive oxygen species, cytokines, and chemokines from an altered microenvironment promote tumor growth. During the last decade, thyroid cancer, the most frequent cancer of the endocrine system, has emerged as the fifth most incident cancer in the United States (USA), and its incidence is steadily growing. Inflammation has long been associated with thyroid cancer, raising critical questions about the role of immune cells in its pathogenesis. A plethora of immune cells and their mediators are present in the thyroid cancer ecosystem. Monoclonal antibodies (mAbs) targeting immune checkpoints, such as mAbs anti-cytotoxic T lymphocyte antigen 4 (anti-CTLA-4) and anti-programmed cell death protein-1/programmed cell death ligand-1 (anti-PD-1/PD-L1), have revolutionized the treatment of many malignancies, but they induce thyroid dysfunction in up to 10% of patients, presumably by enhancing autoimmunity. Combination strategies involving immune checkpoint inhibitors (ICIs) with tyrosine kinase (TK) or serine/threonine protein kinase B-raf (BRAF) inhibitors are showing considerable promise in the treatment of advanced thyroid cancer. This review illustrates how different immune cells contribute to thyroid cancer development and the rationale for the antitumor effects of ICIs in combination with BRAF/TK inhibitors.

[Tumors of the thyroid gland. Proposal for the management and study of samples from patients with thyroid neoplasms]

The recent changes in the classification and staging of thyroid tumors have arisen from the need to provide an adequate response to the exponential increase of thyroid cancer, which, however, has not been accompanied by an increase in mortality. These changes pretend to reduce overdiagnoses of malignancy, unnecessary treatment, side effects as well as cost for the health system. To this end, this article reviews recommendations for the management of thyroid surgical pathology samples with emphasis on the new terminology of the WHO classification. The basic criteria for the diagnosis of malignancy in well-differentiated thyroid carcinomas are reviewed and the criteria for NIFTP (non-invasive follicular tumor with papillary-like nuclear features) diagnosis are updated. Recommendations for the elaboration of the pathological report are also included.