Molecular Correlates and Nuclear Features of Encapsulated Follicular-Patterned Thyroid Neoplasms

Clinicopathologic Features and Cytologic Correlation of ALK-Rearranged Papillary Thyroid Carcinoma: A Series of Eight Cases

Anaplastic lymphoma kinase (ALK) gene fusions are rare in papillary thyroid carcinoma (PTC) but may serve as a therapeutic target. This study aims to evaluate the preoperative cytologic findings and clinicopathologic features of a series of eight ALK-rearranged PTCs from our pathology archives and consultations. All cases were confirmed by ALK D5F3 immunohistochemistry and six with additional targeted RNA-based next-generation sequencing (NGS). The original fine-needle aspiration (FNA) cytology diagnosis included the Bethesda System (TBS) category II in three (37.5%), TBS III in two (25%), TBS V in two (25%), and TBS VI in one (12.5%). Six cases had available FNA cytology and were reviewed. The cytologic features showed microfollicular architecture as well as limited or reduced nuclear elongation and chromatin alterations in all six. Nuclear grooves and pseudoinclusions were absent in two cases, rarely or focally noted in three, and frequently found in one. Two cases initially diagnosed as TBS II, showing microfollicular architecture without well-developed nuclear features, were revised to TBS III (with architectural atypia only). For histologic correlations, four were infiltrative follicular variant PTCs, three as classic subtype PTC with predominant follicular growth, and one as solid/trabecular subtype PTC. All eight cases demonstrated reduced PTC nuclear features with respect to nuclear elongation and chromatin alterations compared to those typically identified in "BRAF-like" PTCs. The NGS testing revealed EML4::ALK fusion in three, STRN::ALK fusion in two, and ITSN2::ALK fusion in one. In conclusion, although ALK-rearranged PTCs have been associated with neutral gene expression profile from a BRAF-RAS scoring perspective, the "RAS-like" nuclear features were more commonly identified in this series, resulting in frequent indeterminate diagnosis of preoperative FNA.

Differentiating BRAF V600E- and RAS-like alterations in encapsulated follicular patterned tumors through histologic features: a validation study

Differentiating BRAF V600E- and RAS-altered encapsulated follicular-patterned thyroid tumors based on morphology remains challenging. This study aimed to validate an 8-score scale nuclear scoring system and investigate the importance of nuclear pseudoinclusions (NPIs) in aiding this differentiation. A cohort of 44 encapsulated follicular-patterned tumors with varying degrees of nuclear atypia and confirmed BRAF V600E or RAS alterations was studied. Nuclear parameters (area, diameter, and optical density) were analyzed using a deep learning model. Twelve pathologists from eight Asian countries visually assessed 22 cases after excluding the cases with any papillae. Eight nuclear features were applied, yielding a semi-quantitative score from 0 to 24. A threshold score of 14 was used to distinguish between RAS- and BRAF V600E-altered tumors. BRAF V600E-altered tumors typically demonstrated higher nuclear scores and notable morphometric alterations. Specifically, the nuclear area and diameter were significantly larger, and nuclear optical density was much lower compared to RAS-altered tumors. Observer accuracy varied, with two pathologists correctly identifying genotype of all cases. Observers were categorized into proficiency groups, with the highest group maintaining consistent accuracy across both evaluation methods. The lower group showed a significant improvement in accuracy upon utilizing the 8-score scale nuclear scoring system, with notably increased sensitivity and negative predictive value in BRAF V600E tumor detection. BRAF V600E-altered tumors had higher median total nuclear scores. Detailed reevaluation revealed NPIs in all BRAF V600E-altered cases, but in only 2 of 14 RAS-altered cases. These results could significantly assist pathologists, particularly those not specializing in thyroid pathology, in making a more accurate diagnosis.

The Asian Thyroid Working Group, from 2017 to 2023

The Asian Thyroid Working Group was founded in 2017 at the 12th Asia Oceania Thyroid Association (AOTA) Congress in Busan, Korea. This group activity aims to characterize Asian thyroid nodule practice and establish strict diagnostic criteria for thyroid carcinomas, a reporting system for thyroid fine needle aspiration cytology without the aid of gene panel tests, and new clinical guidelines appropriate to conservative Asian thyroid nodule practice based on scientific evidence obtained from Asian patient cohorts. Asian thyroid nodule practice is usually designed for patient-centered clinical practice, which is based on the Hippocratic Oath, "First do not harm patients," and an oriental filial piety "Do not harm one's own body because it is a precious gift from parents," which is remote from defensive medical practice in the West where physicians, including pathologists, suffer from severe malpractice climate. Furthermore, Asian practice emphasizes the importance of resource management in navigating the overdiagnosis of low-risk thyroid carcinomas. This article summarizes the Asian Thyroid Working Group activities in the past 7 years, from 2017 to 2023, highlighting the diversity of thyroid nodule practice between Asia and the West and the background reasons why Asian clinicians and pathologists modified Western systems significantly.

Developing Models to Predict BRAFV600E and RAS Mutational Status in Papillary Thyroid Carcinoma Using Clinicopathological Features and pERK1/2 Immunohistochemistry Expression

The Cancer Genome Atlas (TCGA) has classified papillary thyroid carcinoma (PTC) into indolent RAS-like and aggressive BRAF-like based on its distinct driver gene mutations. This retrospective study aimed to assess clinicopathology and pERK1/2 expression variations between BRAF-like and RAS-like PTCs and establish predictive models for BRAFV600E and RAS-mutated PTCs. A total of 222 PTCs underwent immunohistochemistry staining to assess pERK1/2 expression and Sanger sequencing to analyze the BRAF and RAS genes. Multivariate logistic regression was employed to develop prediction models. Independent predictors of the BRAFV600E mutation include a nuclear score of 3, the absence of capsules, an aggressive histology subtype, and pERK1/2 levels exceeding 10% (X2 = 0.128, p > 0.05, AUC = 0.734, p < 0.001). The RAS mutation predictive model includes follicular histology subtype and pERK1/2 expression > 10% (X2 = 0.174, p > 0.05, AUC = 0.8, p < 0.001). We propose using the prediction model concurrently with four potential combination group outcomes. PTC cases included in a combination of the low-BRAFV600E-scoring group and high-RAS-scoring group are categorized as RAS-like (adjOR = 4.857, p = 0.01, 95% CI = 1.470-16.049). PTCs included in a combination of the high-BRAFV600E-scoring group and low-RAS-scoring group are categorized as BRAF-like PTCs (adjOR = 3.091, p = 0.001, 95% CI = 1.594-5.995). The different prediction models indicate variations in biological behavior between BRAF-like and RAS-like PTCs.

Could Oxidative Stress Play a Role in the Development and Clinical Management of Differentiated Thyroid Cancer?

Increased oxidative stress (OS) has been implicated as a relevant risk factor for cancer progression. Furthermore, patients diagnosed with differentiated thyroid cancer (DTC) have been characterized by an increased OS status. Therefore, assessing OS status could potentially be considered a useful tool in DTC clinical management. This measurement could be particularly valuable in personalizing treatment protocols and determining new potential medical targets to improve commonly used therapies. A literature review was conducted to gather new information on DTC clinical management, with a particular focus on evaluating the clinical utility of OS. These meta-analyses concentrate on novel approaches that employ the measurement of oxidative-antioxidant status, which could represent the most promising area for implementing clinical management.

The Presence of Typical "BRAFV600E-Like" Atypia in Papillary Thyroid Carcinoma is Highly Specific for the Presence of the BRAFV600E Mutation

Papillary thyroid carcinomas (PTCs) are driven by a variety of molecular abnormalities including BRAF, RAS, ALK, RET, and NTRK alterations. PTCs driven by the BRAFV600E mutation, or tumours which demonstrate a similar gene expression profile to PTCs driven by this mutation, have been reported to demonstrate specific morphological features sometimes termed "BRAFV600E-like" atypia. BRAFV600E-like atypia is characterised by a well-developed papillary architecture, infiltrative growth, marked nuclear clearing, prominent intranuclear pseudoinclusions, abundant eosinophilic cytoplasm, and scattered psammoma bodies. We sought to investigate the sensitivity and specificity of these morphological features for the presence of BRAFV600E mutation in PTCs as determined by mutation specific immunohistochemistry. An unselected cohort of 495 PTCs was reviewed by a single pathologist and categorised into three groups: typical BRAFV600E-like atypia (145 cases, 29%), possible BRAFV600E-like atypia (166 cases, 33%) and little/no BRAFV600E-like atypia (184 cases, 37%). The specificity and sensitivity of typical BRAFV600E-like atypia for the BRAFV600E mutation was 97.2% and 44.3%, respectively. When typical and possible BRAFV600E-like atypia were analysed together, the specificity was 70.6% and the sensitivity was 81.7%. In the morphologically little/no BRAFV600E-like atypia group, 58 cases (31.5%) had a BRAFV600E mutation. We conclude that typical BRAFV600E-like atypia is highly specific for the presence of the BRAFV600E mutation; however, the absence of BRAFV600E-like atypia does not exclude this mutation.

Update from the 2022 World Health Organization Classification of Thyroid Tumors: A Standardized Diagnostic Approach

The fifth edition of the World Health Organization (WHO) histologic classification of thyroid neoplasms released in 2022 includes newly recognized tumor types, subtypes, and a grading system. Follicular cell-derived neoplasms are categorized into three families (classes): benign tumors, low-risk neoplasms, and malignant neoplasms. The terms "follicular nodular disease" and "differentiated high-grade thyroid carcinoma" are introduced to account for multifocal hyperplastic/neoplastic lesions and differentiated thyroid carcinomas with high-grade features, respectively. The term "Hürthle cells" is replaced with "oncocytic cells." Invasive encapsulated follicular and cribriform morular variants of papillary thyroid carcinoma (PTC) are now redefined as distinct tumor types, given their different genetic alterations and clinicopathologic characteristics from other PTC subtypes. The term "variant" to describe a subclass of tumor has been replaced with the term "subtype." Instead, the term "variant" is reserved to describe genetic alterations. A histologic grading system based on the mitotic count, necrosis, and/or the Ki67 index is used to identify high-grade follicular-cell derived carcinomas and medullary thyroid carcinomas. The 2022 WHO classification introduces the following new categories: "salivary gland-type carcinomas of the thyroid" and "thyroid tumors of uncertain histogenesis." This review summarizes the major changes in the 2022 WHO classification and their clinical relevance.

Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP): Tumour Entity with a Short History. A Review on Challenges in Our Microscopes, Molecular and Ultrasonographic Profile

Since Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP) was introduced as a new thyroid tumour entity, many studies, and meta-analyses on diagnosing NIFTP have been published. NIFTP-revised histopathological criteria emerged in 2018. NIFTP is defined as a histological entity and its diagnosis requires a careful histological examination. Its molecular profile is similar to follicular-like tumours. Ultrasound features are unable to differentiate NIFTP. NIFTP is not a cytological diagnosis, but it influences the risk of malignancy in several categories of The Bethesda System for Reporting Thyroid Cytopathology terminology.

Whole-Slide Imaging: Updates and Applications in Papillary Thyroid Carcinoma

Whole-slide imaging (WSI) has wide spectrum of application in histopathology, especially in the study of cancer including papillary thyroid carcinoma. The main applications of WSI system include research, teaching, and assessment and recently pathology practices. The other major advantages of WSI over histological sections on glass slides are easier storage and sharing of information as well as adaptation of use in artificial intelligence. The applications of WSI depend on factors such as volume of services requiring WSI, physical factors (computer server, bandwidth limitation of networks, storages requirements for data), adaption of the WSI images with the laboratory workflow, personnel (IT expert, pathologist, technicians) adaptation to the WSI workflow, validation studies, ethics, and cost efficiency of the application(s).

The Incidence of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Meta-Analysis Assessing Worldwide Impact of the Reclassification

Background: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification has significantly influenced the field of thyroidology. However, the extent of this impact depends upon the incidence of NIFTP in a given population. In this meta-analysis, we aimed to obtain robust information about the actual incidence of NIFTP worldwide by reviewing the published data. Methods: Comprehensive literature search was performed using electronic databases of PubMed and Web of Science over a five-year period (January 1, 2016, to January 30, 2021). The incidence of NIFTP was calculated by dividing the number of NIFTPs by the number of papillary thyroid carcinomas (PTCs). Meta-analysis of proportion and their 95% confidence interval [CI] were pooled using the random-effect model. Heterogeneity across the included studies was assessed using I² statistics. Egger's regression test and funnel plot of estimates were used to evaluate the publication bias. p-Value <0.05 was considered significant. Results: From 505 publications, we included 50 studies, all retrospective, with 100,780 PTCs and 3990 NIFTP from 92 institutions worldwide. The overall incidence of NIFTP was 6.0% [CI 4.4-8.2] among PTCs or thyroid malignancies with a high level of heterogeneity among the included studies (I² = 98.6%). NIFTP incidence was largely similar in North America and Europe (9.3% vs. 9.6%), with a significantly lower overall rate in Asia (2.1%). There was a significant decline in the reported incidence of NIFTP in non-Asian studies published after 2017 (p = 0.002). On applying our data on global thyroid cancer statistics, this reclassification would affect ∼30,881 patients annually, with a lower impact in Asia compared with North America and Europe. Conclusions: This comprehensive meta-analysis confirms that the worldwide NIFTP incidence is much lower than estimated initially. The NIFTP rates are significantly lower in Asian compared with North American and European countries. Apart from geography, NIFTP rates are significantly influenced by the nature of study, type of database used for sample collection, and the diagnostic criteria used. Introduction of NIFTP may potentially spare over 30,000 patients worldwide annually from clinical and psychological consequences of a thyroid cancer diagnosis.