Not the same thing: metastatic PTCs have a different background than ATCs

Molecular pathology of endocrine gland tumors: genetic alterations and clinicopathologic relevance

Tumors of the endocrine glands are common. Knowledge of their molecular pathology has greatly advanced in the recent past. This review covers the main molecular alterations of tumors of the anterior pituitary, thyroid and parathyroid glands, adrenal cortex, and adrenal medulla and paraganglia. All endocrine gland tumors enjoy a robust correlation between genotype and phenotype. High-throughput molecular analysis demonstrates that endocrine gland tumors can be grouped into molecular groups that are relevant from both pathologic and clinical point of views. In this review, genetic alterations have been discussed and tabulated with respect to their molecular pathogenetic role and clinicopathologic implications, addressing the use of molecular biomarkers for the purpose of diagnosis and prognosis and predicting response to molecular therapy. Hereditary conditions that play a key role in determining predisposition to many types of endocrine tumors are also discussed.

Advances in Thyroid Pathology: High Grade Follicular Cell-derived Thyroid Carcinoma and Anaplastic Thyroid Carcinoma

In the upcoming World Health Organization fifth edition classification of endocrine tumors, there were several major changes related to high grade follicular-derived thyroid carcinoma (HGFCTC) and anaplastic thyroid carcinoma (ATC) based on emerging evidence about the diagnostic criteria clinical behavior, prognostic factors, and molecular signatures of these tumors. In this review, we aim to summarize the major evolutions of HGFCTC and ATC. HGFCTC is a nonanaplastic carcinoma with high grade features (High mitotic count, tumor necrosis). It is subdivided into poorly differentiated thyroid carcinoma diagnosed using the Turin proposal and differentiated high grade thyroid carcinoma. The latter is defined by the presence of the cytoarchitectutal features of well-differentiated thyroid carcinoma (eg, papillae) but harbors elevated mitotic activity and/or tumor necrosis. Poorly differentiated thyroid carcinoma is predominantly RAS -driven and associated with RAI avidity and high propensity for distant metastasis, whereas differentiated high grade thyroid carcinoma is mostly BRAFV600E -driven. ATC may show a wide range of histologic features. Carcinoma of pure squamous phenotype is associated with a high frequency of BRAF V600E mutations and is now considered as a subtype of ATC. There is a stepwise molecular progression from well-differentiated carcinoma to HGFCTC to ATC manifested by 1) early and persistent driver alteration in the MAPK pathway, particularly BRAF V600E and RAS mutations, and 2) gain of secondary aggressive molecular signatures (such as TERT promoter and TP53 mutations) when tumors progress from well-differentiated to high grade to anaplastic carcinoma.

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.

S100A1 is a Potential Biomarker for Papillary Thyroid Carcinoma Diagnosis and Prognosis

S100 calcium binding protein A1 (S100A1) is an important member of the S100 family and known to express in a variety of cancers. However, the biological functions of S100A1 in thyroid carcinoma have not been thoroughly studied. In this report, bioinformatics analyses and immunohistochemistry assays were applied to assess the expression profile of S100A1 as well as its relationship with the pathological features and prognosis of papillary thyroid carcinoma (PTC). Meanwhile, functions of S100A1 in PTC cells were analyzed with either in vitro or in vivo experiments. S100A1 was significantly up-regulated in PTC tissues compared with adjacent non-cancerous tissues. S100A1 protein expression was significantly associated with tumor size (p=0.0032) or lymph node metastasis (p=0.0331). More importantly, an elevated S100A1 expression was significantly correlated with a worse recurrence-free survival (RFS) (HR=2.26, p=0.042). Further, knockdown of S100A1 dramatically inhibited cell proliferation and migration as well as increased apoptosis of PTC cells. S100A1 knockdown inhibited tumor progression as seen in in vivo experiments. In terms of mechanism, down-regulation of S100A1 induced yes associated protein (YAP) phosphorylation in the cytoplasm and diminished Hippo/YAP pathway activation. Therefore, S100A1 may serve as a novel oncogene and a promising biomarker for PTC diagnosis and prognosis.

Novel Recurrent Altered Genes in Chinese Patients With Anaplastic Thyroid Cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is a rare but lethal malignancy, and few systematic investigations on genomic profiles of ATC have been performed in Chinese patients.

METHODS

Fifty-four ATC patients in West China Hospital between 2010 to 2020 were retrospectively analyzed, while 29 patients with available samples were sequenced by whole-exome sequencing (WES). The associations between genomic alterations and clinical characteristics were statistically evaluated.

RESULTS

The median overall survival was 3.0 months in the entire cohort, which was impacted by multiple clinical features, including age, tumor size, and different treatment strategies. In the WES cohort, totally 797 nonsilent mutations were detected; the most frequently altered genes were TP53 (48%), BRAF (24%), PIK3CA (24%), and TERT promoter (21%). Although these mutations have been well-reported in previous studies, ethnic specificity was exhibited in terms of mutation frequency. Moreover, several novel significantly mutated genes were identified including RBM15 (17%), NOTCH2NL (14%), CTNNA3 (10%), and KATNAL2 (10%). WES-based copy number alteration analysis also revealed a high frequent gain of NOTCH2NL (41%), which induced its increased expression. Gene mutations and copy number alterations were enriched in phosphatidylinositol 3-kinase/AKT/mechanistic target of rapamycin (mTOR), NOTCH, and WNT pathways.

CONCLUSIONS

This study reveals shared and ethnicity-specific genomic profiles of ATC in Chinese patients and suggests NOTCH2NL may act as a novel candidate driver gene for ATC tumorigenesis.

Molecular Pathology of Poorly Differentiated and Anaplastic Thyroid Cancer: What Do Pathologists Need to Know?

The molecular characterization of poorly and anaplastic thyroid carcinomas has been greatly improved in the last years following the advent of high throughput technologies. However, with special reference to genomic data, the prevalence of reported alterations is partly affected by classification criteria. The impact of molecular pathology in these tumors is multifaceted and bears diagnostic, prognostic, and predictive implications although its use in the clinical practice is not completely assessed. Genomic profiling data claim that genetic alterations in poorly differentiated and anaplastic thyroid carcinomas include "Early" and "Late" molecular events, which are consistent with a multi-step model of progression. "Early" driver events are mostly RAS and BRAF mutations, whereas "Late" changes include above all TP53 and TERT promoter mutations, as well as dysregulation of gene involved in the cell cycle, chromatin remodeling, histone modifications, and DNA mismatch repair. Gene fusions are rare but represent relevant therapeutic targets. Epigenetic modifications are also playing a relevant role in poorly differentiated and anaplastic thyroid carcinomas, with altered regulation of either genes by methylation/deacetylation or non-coding RNAs. The biological effects of epigenetic modifications are not fully elucidated but interfere with a wide spectrum of cellular functions. From a clinical standpoint, the combination of genomic and epigenetic data shows that several molecular alterations affect druggable cellular pathways in poorly differentiated and anaplastic thyroid carcinomas, although the clinical impact of molecular typing of these tumors in terms of predictive biomarker testing is still under exploration.

Linc00941 Is a Novel Transforming Growth Factor β Target That Primes Papillary Thyroid Cancer Metastatic Behavior by Regulating the Expression of Cadherin 6

Background: Papillary thyroid cancers (PTCs) are common, usually indolent malignancies. Still, a small but significant percentage of patients have aggressive tumors and develop distant metastases leading to death. Currently, it is not possible to discriminate aggressive lesions due to lack of prognostic markers. Long noncoding RNAs (lncRNAs), which are selectively expressed in a context-dependent manner, are expected to represent a new landscape to search for molecular discriminants. Transforming growth factor β (TGFβ) is a multifunctional cytokine that fosters epithelial-to-mesenchymal transition and metastatic spreading. In PTCs, it triggers the expression of the metastatic marker Cadherin 6 (CDH6). Here, we investigated the TGFβ-dependent lncRNAs that may cooperate to potentiate PTC aggressiveness. Methods: We used a genome-wide approach to map enhancer (ENH)-associated lncRNAs under TGFβ control. Linc00941 was selected and validated using functional in vitro assays. A combined approach using bioinformatic analyses of the thyroid cancer (THCA)-the cancer genome atlas (TCGA) dataset and RNA-seq analysis was used to identify the processes in which linc00941 was involved in and the genes under its regulation. Correlation with clinical data was performed to evaluate the potential of this lncRNA and its targets as prognostic markers in THCA. Results: Linc00941 was identified as transcribed starting from one of the TGFβ-induced ENHs. Linc00941 expression was significantly higher in aggressive cancer both in the TCGA dataset and in a separate validation cohort from our institution. Loss of function assays for linc00941 showed that it promotes response to stimuli and invasiveness while restraining proliferation in PTC cells, a typical phenotype of metastatic cells. From the integration of TCGA data and linc00941 knockdown RNA-seq profiling, we identified 77 genes under the regulation of this lncRNA. Among these, we found the prometastatic gene CDH6. Linc00941 knockdown partially recapitulates the effects observed upon CDH6 silencing, promoting cell cytoskeleton and membrane adhesions rearrangements and autophagy. The combined expression of CDH6 and linc00941 is a distinctive feature of highly aggressive PTC lesions. Conclusions: Our data provide new insights into the biology driving metastasis in PTCs and highlight how lncRNAs cooperate with coding transcripts to sustain these processes.

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.

Dissecting Anaplastic Thyroid Carcinoma: A Comprehensive Clinical, Histologic, Immunophenotypic, and Molecular Study of 360 Cases

Background: Anaplastic thyroid carcinoma (ATC) is nearly always fatal. Large studies on ATC are exceedingly rare. We aimed to study the clinical, genotypic, and histologic characteristics of ATC in the largest retrospective cohort of ATC to date. Methods: Three hundred sixty patients with ATC from two tertiary centers were studied. Molecular testing was performed in 126 cases including 107 using next-generation sequencing. Results: The median patients' age was 68 years. Differentiated thyroid carcinoma (DTC) was present in 208 cases (58%), the most common being papillary carcinoma (n = 150). The 1-, 2-, 3-, and 5-year overall survival (OS) was 36%, 17%, 13%, and 11%, respectively. On univariate analysis, age, resectability, chemotherapy, radiotherapy, margin status, encapsulation, gross residual disease, gross extrathyroidal extension, percentage, and size of ATC in the primary tumor predicted OS (p < 0.05). Age, resectability, chemotherapy, and gross residual disease were independent prognostic factors in the entire cohort, while gross residual disease was the only independent predictor of OS in patients who had resection of their tumor. BRAF, RAS, TERT promoter, TP53, PIK3CA, E1F1AX, and PTEN mutations were detected in 45%, 24%, 75%, 63%, 18%, 14%, and 14% of ATC, respectively. Concomitant BRAF/RAS and TERT mutations were associated with worse outcome than mutation in only one of the genes. BRAF-mutated and RAS-mutated ATCs had similar frequency of nodal and distant metastasis. Twelve cases were pure squamous cell carcinoma, 60% of which carried BRAF^V600E mutation and showed a similar OS to other ATCs. Conclusions: (i) Gross residual disease remains the most crucial indicator of outcome in ATC. (ii) Encapsulation, margin status, percentage, and size of ATC in the primary were prognostically relevant. (iii) Pure thyroid squamous cell carcinoma may be considered as ATC given a BRAF^V600E genotype and similar outcome. (iv) In contrast to DTC, BRAF-mutated and RAS-mutated ATCs have similar metastatic spread. (v) Concomitant mutations of BRAF or RAS with TERT confer a worse prognosis.

Molecular Diagnostic of Solid Tumor Using a Next Generation Sequencing Custom-Designed Multi-Gene Panel

Next generation sequencing (NGS) allows parallel sequencing of multiple genes at a very high depth of coverage. The need to analyze a variety of targets for diagnostic/prognostic/predictive purposes requires multi-gene characterization. Multi-gene panels are becoming standard approaches for the molecular analysis of solid lesions. We report a custom-designed 128 multi-gene panel engineered to cover the relevant targets in 22 oncogene/oncosuppressor genes for the analysis of the solid tumors most frequently subjected to routine genotyping. A total of 1695 solid tumors were analyzed for panel validation. The analytical sensitivity is 5%. Analytical validation: (i) Accuracy: sequencing results obtained using the multi-gene panel are concordant using two different NGS platforms and single-gene approach sequencing (100% of 83 cases); (ii) Precision: consistent results are obtained in the samples analyzed twice with the same platform (100% of 20 cases). Clinical validation: the frequency of mutations identified in different tumor types is consistent with the published literature. This custom-designed multi-gene panel allows to analyze with high sensitivity and throughput 22 oncogenes/oncosuppressor genes involved in diagnostic/prognostic/predictive characterization of central nervous system tumors, non-small-cell lung carcinomas, colorectal carcinomas, thyroid nodules, pancreatic lesions, melanoma, oral squamous carcinomas and gastrointestinal stromal tumors.

Whole-Exome Sequencing of Matched Primary and Metastatic Papillary Thyroid Cancer

Background: Distant metastasis is a rare occurrence in thyroid cancer, and it can be associated with poor prognosis. The genomic repertoires of various solid malignancies have previously been reported but remain underexplored in metastatic papillary thyroid cancer (PTC). Furthermore, whether distant metastases harbor distinct genetic alterations beyond those observed in primary tumors is unknown. Methods: We performed whole-exome sequencing on 14 matched distant metastases, primary PTC tumors, and normal tissues. Point mutations, copy number alterations, cancer cell fractions, and mutational signatures were defined using the state-of-the-art bioinformatics methods. All likely deleterious variants were validated by orthogonal methods. Results: Genomic differences were observed between primary and distant metastatic deposits, with a median of 62% (range 21-92%) of somatic mutations detected in metastatic tissues, but absent from the corresponding primary tumor sample. Mutations in known driver genes including BRAF, NRAS, and HRAS were shared and preferentially clonal in both sites. However, likely deleterious variants affecting DNA methylation and transcriptional repression signaling genes including SIN3A, RBBP1, and CHD4 were found to be restricted in the metastatic lesions. Moreover, a mutational signature shift was observed between the mutations that are specific or enriched in the metastatic and primary lesions. Conclusions: Primary PTC and distant metastases differ in their range of somatic alterations. Genomic analysis of distant metastases provides an opportunity to identify potentially clinically informative alterations not detected in primary tumors, which might influence decisions for personalized therapy in PTC patients with distant metastasis.

Immunomorphology and molecular biology of mixed primary liver cancers: is Nestin a marker of intermediate-cell carcinoma?

AIMS

Primary mixed liver cancers (PLCs), combined hepatocellular-cholangiocellular (cHCC-CC) and intermediate-cell carcinomas are rare tumours characterised by different molecular mechanisms. Nestin is a marker of progenitor cells with a promising application in human tumours. The aims of the present paper are (i) to determine the expression of Nestin in mixed PLCs; and (ii) to correlate the PLC immunoprofile with the gene expression in each tumour component.

METHODS AND RESULTS

We selected 28 mixed PLCs, 13 (46.4%) cHCC-CC and 15 (53.6%) intermediate-cell carcinomas. The immunohistochemistry panel consisted of keratin 7, keratin 19, CD56 and Nestin. Next-generation sequencing analysis was performed on 17 cases (27 specimens) using a multi-gene custom panel. The differentiated HCC and CC components of cHCC-CC were negative for Nestin in all cases. The intermediate areas of cHCC-CC were immunoreactive for Nestin in 92.3% of cases, for CD56 in 76.9% and for K7/K19 in all cases. The immunoprofile of the intermediate-cell carcinomas showed 73.3% of cases positive for Nestin and 66.7% for CD56. TP53 and TERT were the most frequently mutated genes (31.3% and 17.6% of samples, respectively). Mutations were also found in IDH1, IDH2, PIK3CA and NRAS genes. Intermediate and HCC areas of cHCC-CC seemed to share the same mutational profile, and both harboured different mutations than the CC component.

CONCLUSIONS

According to our preliminary data, Nestin was not expressed by hepatocellular or cholangiocellular-cell components, but was expressed by most of the intermediate cells in PLCs, and therefore could be considered in the differential diagnosis of PLCs, together with mutational profile.

Telomerase and Telomeres Biology in Thyroid Cancer

Telomere and telomerase regulation contributes to the onset and evolution of several tumors, including highly aggressive thyroid cancers (TCs). TCs are the most common endocrine malignancies and are generally characterized by a high rate of curability. However, a small but significant percentage develops distant metastasis or progresses into undifferentiated forms associated with bad prognosis and for which poor therapeutic options are available. Mutations in telomerase reverse transcriptase (TERT) promoter are among the most credited prognostic marker of aggressiveness in TCs. Indeed, their frequency progressively increases passing from indolent lesions to aggressive and anaplastic forms. TERT promoter mutations create binding sites for transcription factors, increasing TERT expression and telomerase activity. Furthermore, aggressiveness of TCs is associated with TERT locus amplification. These data encourage investigating telomerase regulating pathways as relevant drivers of TC development and progression to foster the identification of new therapeutics targets. Here, we summarize the current knowledge about telomere regulation and TCs, exploring both canonical and less conventional pathways. We discuss the possible role of telomere homeostasis in mediating response to cancer therapies and the possibility of using epigenetic drugs to re-evaluate the use of telomerase inhibitors. Combined treatments could be of support to currently used therapies still presenting weaknesses.

Identification of Targetable Lesions in Anaplastic Thyroid Cancer by Genome Profiling

Anaplastic thyroid cancer (ATC) is a rare and extremely malignant tumor with no available cure. The genetic landscape of this malignancy has not yet been fully explored. In this study, we performed whole exome sequencing and the RNA-sequencing of fourteen cases of ATC to delineate copy number changes, fusion gene events, and somatic mutations. A high frequency of genomic amplifications was seen, including 29% of cases having amplification of CCNE1 and 9% of CDK6; these events may be targetable by cyclin dependent kinase (CDK) inhibition. Furthermore, 9% harbored amplification of TWIST1, which is also a potentially targetable lesion. A total of 21 fusion genes in five cases were seen, none of which were recurrent. Frequent mutations included TP53 (55%), the TERT promoter (36%), and ATM (27%). Analyses of mutational signatures showed an involvement of processes that are associated with normal aging, defective DNA mismatch repair, activation induced cytidine deaminase (AID)/apolipoprotein B editing complex (APOBEC) activity, failure of DNA double-strand break repair, and tobacco exposure. Taken together, our results shed new light on the tumorigenesis of ATC and show that a relatively large proportion (36%) of ATCs harbor genetic events that make them candidates for novel therapeutic approaches. When considering that ATC today has a mortality rate of close to 100%, this is highly relevant from a clinical perspective.