Encapsulated follicular thyroid tumor with equivocal nuclear changes, so-called well-differentiated tumor of uncertain malignant potential: a morphological, immunohistochemical, and molecular appraisal

Seven years of Non-invasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP): Rate of Acceptance and Variation of Diagnostic Approaches Across Different Continents

CONTEXT

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced as a new entity replacing the diagnosis of noninvasive encapsulated follicular variant of papillary thyroid carcinoma (PTC). Significant variability in the incidence of NIFTP diagnosed in different world regions has been reported.

OBJECTIVE

To investigate the rate of adoption of NIFTP, change in practice patterns, and uniformity in applying diagnostic criteria among pathologists practicing in different regions.

METHODS

Two surveys distributed to pathologists of the International Endocrine Pathology Discussion Group with multiple-choice questions on NIFTP adoption into pathology practice and whole slide images of 5 tumors to collect information on nuclear score and diagnosis. Forty-eight endocrine pathologists, including 24 from North America, 8 from Europe, and 16 from Asia/Oceania completed the first survey and 38 the second survey.

RESULTS

A 94% adoption rate of NIFTP by the pathologists was found. Yet, the frequency of rendering NIFTP diagnosis was significantly higher in North America than in other regions (P = .009). While the highest concordance was found in diagnosing lesions with mildly or well-developed PTC-like nuclei, there was significant variability in nuclear scoring and diagnosing NIFTP for tumors with moderate nuclear changes (nuclear score 2) (case 2, P < .05). Pathologists practicing in North America and Europe showed a tendency for lower thresholds for PTC-like nuclei and NIFTP than those practicing in Asia/Oceania.

CONCLUSION

Despite a high adoption rate of NIFTP across geographic regions, NIFTP is diagnosed more often by pathologists in North America. Significant differences remain in diagnosing intermediate PTC-like nuclei and respectively NIFTP, with more conservative nuclear scoring in Asia/Oceania, which may explain the geographic differences in NIFTP incidence.

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.

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.

Investigation of pre-operative demographic, biochemical, sonographic and cytopathological findings in low-risk thyroid neoplasms

OBJECTIVE

The present article analyses pre-operative demographic, biochemical, sonographic and histopathological characteristics of low-risk thyroid neoplasms (LRTNs), with a focus on four subgroups, "well-differentiated carcinoma-not otherwise specified" (WDC-NOS), "non-invasive follicular thyroid neoplasm with papillary like nuclear features" (NIFTP), "well-differentiated tumours of uncertain malignant potential" (WDT-UMP) and "follicular tumour of uncertain malignant potential" (FT-UMP).

METHODS

The study retrospectively analyzed the histopathology of 2453 malignant thyroids and the final analyses included 99 cases diagnosed with LRTNs. The demographic and clinical features, pre-operative thyroid function, ultrasonography results, cytopathology results, histopathology results and prognostic classifications were assessed.

RESULTS

The groups were similar demographic characteristics and the majority of clinical data, including comorbidities, thyroid function tests, thyroid cancer/neck radiotherapy history. NIFTPs represented 69.7% of all LRTNs. All (100%) WDT-UMPs had solitary nodules. Index nodule volume differed among the groups (p = .036), it was the lowest in WDC-NOS [0.68 (0.63-0.72 cc)] and highest in FT-UMP [12.6 (0.5-64 cc)]. Echogenicity findings were similar. Index nodule TIRADS demonstrated a significant difference (p = .021) but index nodule halo sign and BETHESDA scores were similar in all groups. The diameter, localisation and multicentric structure of LRTNs were again similar for all groups. Finally, prognostic scores suggested similar outcomes in all groups.

CONCLUSION

The majority of LRTNs were NIFTPs in our population and all WDT-UMPs were solitary lesions. Index nodule volume was the most essential discriminating sonographic finding but further research must be performed before discriminatory potential can be described.

Challenges in Encapsulated Follicular-Patterned Tumors: How Much Is Enough? Evaluation of Nuclear Atypia, Architecture, and Invasion

Thyroid pathology is notoriously fraught with high interobserver variability, and follicular-patterned tumors are among some of the most challenging to assess accurately and reproducibly. Given that encapsulated or well-circumscribed follicular-patterned tumors often have similar molecular profiles, that is, frequent RAS or RAS-like alterations, the diagnosis usually relies on histopathologic examination alone. Unfortunately, many of the features that are used for diagnosis and prognosis of these tumors have long been controversial and frequently debated topics, both due to their subjectivity and their evolving (or not yet resolved) definitions. In more recent years, the introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features has added further complexity to this discussion. In particular, the criteria and significance of nuclear features of papillary thyroid carcinoma, architectural patterns, and invasive growth still pose significant diagnostic challenges and confusion. This review explores some of the challenges in evaluating encapsulated follicular-patterned tumors, focusing on those histologic elements.

Chondroblastoma: clinicopathological analyses of 307 cases from a single institution in China and the diagnostic value of the H3F3 K36M mutant antibody

AIMS

To elucidate the clinicopathological features and the diagnostic value of mutation specific antibody H3F3 K36M of chondroblastoma (CB) in China.

METHODS

Clinicopathological profiles were retrieved, and immunohistochemistry was performed on 185 CB specimens and the control group.

RESULTS

Our series included 307 patients with a mean age of 22.1 years. Long tubular bones (63.8%, 196/307) were most commonly involved, followed by short bones of the hands and feet (22.1%, 68/307), sesamoid bones (8.1%, 25/307), flat bones and irregular bones (5.9%, 18/307). The most commonly involved site was the proximal femur, followed by distal femur, proximal humerus and calcaneus. The average age in the long bones group (20.3 years) was significantly younger than the short bones group (24.9 years) (p<0.001), sesamoid bones group (24.4 years) (p=0.02) and flat bones and irregular bones group (29.1 years) (p<0.001). Microscopically, aneurysmal bone cyst-like change (63.6%, 117/184), necrosis (43.5%, 80/184) and chicken-wire calcification (26.1%, 48/184) were variably noted. In rare cases, cortical destruction, soft tissue and lymphovascular invasion were identified. Positive immunoreaction with H3F3 K36M was examined in all non-decalcified, all EDTA decalcified, 87.1% hydrochloric acid (HCl) decalcified CB samples and the high-grade sarcoma secondary to CB, but not the control group.

CONCLUSIONS

CB usually involves the long tubular bones in younger age group. H3F3 K36M can identify K36M mutation with 100% specificity and 100% sensitivity in non-decalcified and EDTA decalcified samples, more than 80% sensitivity in HCl decalcified samples. Virtually, all CBs harbour an H3K36M mutation.

Variation in the Diagnosis of Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features

CONTEXT

Noninvasive encapsulated follicular variant of papillary thyroid cancer was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in January 2017. The impact of this nomenclature change at a population level remains unknown.

OBJECTIVE

Examine use of NIFTP across different US regions and populations.

DESIGN

Descriptive epidemiology study using SEER-22 data (2000-2019).

PARTICIPANTS

Individuals diagnosed with papillary or follicular thyroid cancer (2000-2019) or NIFTP (2017-2019).

MAIN OUTCOME MEASURES

Annual incidence rates of thyroid cancer by subtype and NIFTP. Using 2018-2019 data, (1) rates of NIFTP at the 17 SEER-22 sites and (2) comparison of demographics for patients diagnosed with NIFTP vs papillary and follicular thyroid cancer.

RESULTS

NIFTP comprised 2.2% and 2.6% of cases in 2018 and 2019, respectively. Between 2018 and 2019, large heterogeneity was observed in the regional use of NIFTP diagnosis, with site-specific incidence rates between 0.0% and 6.2% (median 2.8%, interquartile range 1.3-3.6%). A diagnosis of NIFTP (vs papillary and follicular thyroid cancer) in 2018 and 2019 was significantly associated with older age (P = 0.012 and P = 0.009, respectively), Black race (both Ps < 0.001), and non-Hispanic ethnicity (both Ps < 0.001).

CONCLUSIONS

Marked variation exists in the use of the NIFTP diagnosis. The recent 2021 coding change that resulted in NIFTP, a tumor with uncertain malignant potential and for which there is no long-term outcome data available, no longer being a reportable diagnosis to SEER will disproportionately affect vulnerable patient groups such as older patients and Black patients, in addition to patients who reside in regions with higher rates of NIFTP diagnoses.

The Autoantibodies against Tumor-Associated Antigens as Potential Blood-Based Biomarkers in Thyroid Neoplasia: Rationales, Opportunities and Challenges

The Autoantibodies targeting Tumor-Associated Antigens (TAA-AAbs) emerge as a result of a variety of tumor-related immunogenic stimuli and may be regarded as the eyewitnesses to the anti-tumor immune response. TAA-AAbs may be readily detected in peripheral blood to unveil the presence of a particular TAA-expressing tumor, and a fair number of TAAs eliciting the tumor-associated autoantibody response have been identified. The potential of TAA-AAbs as tumor biomarkers has been extensively studied in many human malignancies with a major influence on public health; however, tumors of the endocrine system, and, in particular, the well-differentiated follicular cell-derived thyroid neoplasms, remain understudied in this context. This review provides a detailed perspective on and legitimate rationales for the potential use of TAA-AAbs in thyroid neoplasia, with particular reference to the already established diagnostic implications of the TAA-AAbs in human cancer, to the windows for improvement and diagnostic niches in the current workup strategies in nodular thyroid disease and differentiated thyroid cancer that TAA-AAbs may successfully occupy, as well as to the proof-of-concept studies demonstrating the usefulness of TAA-AAbs in thyroid oncology, particularly for the pre-surgical discrimination between tumors of different malignant potential in the context of the indeterminate results of the fine-needle aspiration cytology.

Noninvasive Follicular Tumor With Papillary-like Nuclear Features: A Practice Changer in Thyroid Pathology

CONTEXT.—

This article presents a review of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), including its separation from follicular variant of papillary carcinoma of the thyroid, its evolution, and current definition and pathologic characteristics.

OBJECTIVES.—

To emphasize the understanding of the concept of NIFTP as a neoplasm based on molecular analyses, its critical histopathologic features, the microscopic findings that exclude the diagnosis, and the importance of complete sectioning of the tumor to exclude neoplasms that should be diagnosed as carcinomas. Important distinctions are discussed including difficulties with literature that shows NIFTP with metastases, inadequacy of sectioning of the tumor, and lack of descriptive histology of the surrounding thyroid and possible other lesions.

DATA SOURCES.—

Review of articles in the English literature on NIFTP, as well as comparative papers showing differences and distinctions between this entity and papillary carcinomas.

CONCLUSIONS.—

This article concludes that with the current state of knowledge on NIFTP with studies from all over the world, this entity is a low-risk neoplasm that, when diagnosed using appropriate criteria, should not be associated with metastatic or recurrent disease, at least on intermediate length of follow-up. This review includes discussion of multifocal NIFTP, as well as the recently defined micro-NIFTP (1 cm or less), and describes features of the tumor that remain to be studied and correlated with outcome: oncocytic variants of NIFTP, percentage of allowable solid areas of growth in the lesions, and definitions of true neoplastic papillae and hyperplastic ones and how these should influence the diagnosis of NIFTP.

Additional Tissue Sampling Trials Did Not Change Our Thyroid Practice

Simple Summary

Some studies have suggested that the use of additional tissue blocks to diagnose follicular thyroid carcinoma (FTC) could increase the accuracy of diagnosis and improve prognosis, and entire capsule sampling was recommended for a definitive diagnosis of borderline thyroid tumors in 2016. We conducted a study in 2016 to examine whether additional tissue sampling of the encapsulated follicular tumor increases the diagnosis of malignant cases in our patient cohort. Furthermore, the diagnosis was reclassified according to the 4th edition of the World Health Organization’s classification system. The additional tissue sampling only had a slight impact on our thyroid practice and resulted in no benefits to the patient; therefore, we decided to cease it.

Abstract

This study aimed to determine whether additional tissue sampling of encapsulated thyroid nodules would increase the frequency of follicular thyroid carcinoma (FTC) diagnoses. We examined thyroid tissue specimens from 86 patients suspected of FTC (84.9% female; mean age, 49.0 ± 17.8 years). The number of tissue blocks created for pathological assessments ranged from 3 to 20 (mean, 9.1 ± 4.1); the numbers in the previous method recommended by the Japanese General Rules for the Description of Thyroid Cancer and additional blocks ranged from 1 to 12 (mean, 6.0 ± 2.8) and from 1 to 8 (mean, 3.1 ± 2.0), respectively. The additional blocks were subsequently examined to determine whether any diagnoses changed from those based on the previous method. Five patients were diagnosed with FTC using the previous method; however, additional tissue blocks led to the diagnosis of FTC in 6 patients, as 1 diagnosis was revised from follicular adenoma to FTC. It has been reported that increasing the number of tissue blocks used for pathological assessments can increase the frequency of FTC diagnoses; however, this was not clinically significant in thyroid carcinoma, which requires completion thyroidectomy and radioactive iodine treatment. It resulted in no benefits to the patient because all minimally invasive FTCs, follicular tumors of uncertain malignant potential (FT-UMP), and follicular adenomas are treated with lobectomy alone in Japan. Additional tissue sampling only had a slight impact on our thyroid practice; therefore, we decided to cease it.

The effect of implementing pre-surgical ultrasound-guided fine-needle aspiration biopsy on thyroid surgery, a 6-year interrupted time series analysis in Qilu Hospital of Shandong University

Background

Thyroid fine-needle aspiration biopsy (FNAB) is not well developed in most of the large academic hospitals in China, including Qilu Hospital of Shandong University. Ultrasound-guided FNAB (UG-FNAB) was initiated as a pre-surgical diagnostic method in 2015 in Qilu Hospital, and the current study evaluates its impact on the number of thyroid surgeries and the ratio of malignancy (ROM) in surgically resected cases, comparing the post and pre-UG-FNAB periods.

Methods

Thyroid surgery and UG-FNAB data for the study period (Jan 2013 to Dec 2018) were collected from the hospital information system (HIS). A natural experimental approach using segmented linear regression was performed on the interrupted time-series (ITS) data to estimate the level-change of the number and the trend-change of ROM of surgically resected cases following the implementation of UG-FNAB diagnosis.

Results

The number of UG-FNAB cases in Qilu Hospital increased rapidly from 1,367 in 2015 to 3,402 in 2018, with an average annual increase of 678 cases. Comparing the pre-UG-FNAB and post-UG-FNAB periods, the overall ROM of thyroid resections increased from 58.7% to 73.2% (P<0.01). Due to the implementation of UG-FNAB, the regression line of surgical cases showed an inflection point in March 2015, and the slope of the regression line of post-intervention was lower than that of pre-intervention. For each additional month, the ROM in thyroid surgical cases increased by 0.389% (P<0.01). After excluding the influence of time, the ROM in surgically resected thyroid cases increased by 4.781% due to the application of the UG-FNAB examination (P<0.01).

Conclusions

This successful implementation of UG-FNAB further improved overall ROMs in surgically resected cases particularly as we acquired further experience with the procedure and reduced unnecessary diagnostic surgeries for patients with benign and borderline lesions.

Precursor and borderline lesions of the thyroid (indolent lesions of epithelial origin): from theory to practice

The precursor lesions of thyroid neoplasms can arise from either C cells or follicular cells. Although MTC has an established and recognized precursor lesion, the C-cell hyperplasia, the same does not occur for the follicular cell-derived tumors, which are much more frequent. One of the significant obstacles to recognizing follicular cell-derived precursor lesions (FCPL) is the lack of refinement of the morphological spectrum and biology of these putative premalignant lesions. What are the "gold standard" histological criteria in thyroid pathology to identify the progression of dysplasia to cancer? Diagnostical irreproducibility and misnomer in the terminology of some FCPLs have been lying behind the answer to this question. The last past decades' advances in molecular pathology allow us to transform the knowledge in thyroid pathology to cancer prevention and early detection, which will only be possible by improving our understanding of the nature of thyroid precursor and borderline lesions. This review, amassed with the augmented expertise of thyroid pathology documented in the literature, is an attempt at underlining the present understanding of precursor and borderline lesions of the thyroid, with a particular highlight on practice differences in Asian and Western geographies.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: From Echography to Genetic Profile

In thyroid pathology, the great variety of types and the wide range of aggressiveness of thyroid cancers complicate both diagnosis and management. In 2016, a subset of noninvasive encapsulated follicular variant of papillary thyroid carcinoma was reclassified as noninvasive follicular thyroid tumor with papillary-like nuclear features (NIFTP) to reduce overtreatment of this low-risk tumor that follows a benign course after surgery. Starting from a paradigmatic clinical case, in this short review, we will summarize the ultrasonography, cytological, histological and molecular features of this new entity. In the preoperative settings, the recognition of some peculiar elements may only suggest the possibility of a NIFTP, thus favoring a less aggressive surgical approach. However, the diagnosis of NIFTP can only be made after complete resection of the lesion by detecting well-defined inclusion and exclusion histopathological criteria. Since NIFTP is not 'malignant,' surgery may be considered curative with no further treatment or surveillance needed. NIFTP-related issues, including nodule size, multifocality, oncocytic changes, heterogeneous incidence across different geographical areas and its occurrence in the pediatric age, will be discussed.

Multi-dimensional immunoproteomics coupled with in vitro recapitulation of oncogenic NRASQ61R identifies diagnostically relevant autoantibody biomarkers in thyroid neoplasia

Tumor-associated antigen (TAA)-specific autoantibodies have been widely implicated in cancer diagnosis. However, cancer cell lines that are typically exploited as candidate TAA sources in immunoproteomic studies may fail to accurately represent the autoantigen-ome of lower-grade neoplasms. Here, we established an integrated strategy for the identification of disease-relevant TAAs in thyroid neoplasia, which combined NRAS^Q61R oncogene expression in non-tumorous thyroid Nthy-ori 3-1 cells with a multi-dimensional proteomic technique DISER that consisted of profiling NRAS^Q61R-induced proteins using 2-dimensional difference gel electrophoresis (2D-DIGE) coupled with serological proteome analysis (SERPA) of the TAA repertoire of patients with thyroid encapsulated follicular-patterned/RAS-like phenotype (EFP/RLP) tumors. We identified several candidate cell-based (nicotinamide phosphoribosyltransferase NAMPT, glutamate dehydrogenase GLUD1, and glutathione S-transferase omega-1 GSTO1) and autoantibody (fumarate hydratase FH, calponin-3 CNN3, and pyruvate kinase PKM autoantibodies) biomarkers, including NRAS^Q61R-induced TAA phosphoglycerate kinase 1 PGK1. Meta-profiling of the reactivity of the identified autoantibodies across an independent SERPA series implicated the PKM autoantibody as a histological phenotype-independent biomarker of thyroid malignancy (11/38 (29%) patients with overtly malignant and uncertain malignant potential (UMP) tumors vs 0/22 (p = 0.0046) and 0/20 (p = 0.011) patients with non-invasive EFP/RLP tumors and healthy controls, respectively). PGK1 and CNN3 autoantibodies were identified as EFP/RLP-specific biomarkers, potentially suitable for further discriminating tumors with different malignant potential (PGK1: 7/22 (32%) patients with non-invasive EFP/RLP tumors vs 0/38 (p = 0.00044) and 0/20 (p = 0.0092) patients with other tumors and healthy controls, respectively; СNN3: 9/29 (31%) patients with malignant and borderline EFP/RLP tumors vs 0/31 (p = 0.00068) and 0/20 (p = 0.0067) patients with other tumors and healthy controls, respectively). The combined use of PKM, CNN3, and PGK1 autoantibodies allowed the reclassification of malignant/UMP tumor risk in 19/41 (46%) of EFP/RLP tumor patients. Taken together, we established an experimental pipeline DISER for the concurrent identification of cell-based and TAA biomarkers. The combination of DISER with in vitro oncogene expression allows further targeted identification of oncogene-induced TAAs. Using this integrated approach, we identified candidate autoantibody biomarkers that might be of value for differential diagnostic purposes in thyroid neoplasia.

Mutation profiles of follicular thyroid tumors by targeted sequencing

Background

One of the major challenges remaining in the classification of thyroid tumor is the determination of whether a nodule is benign or malignant. We aimed to characterize the mutational profiles of follicular thyroid tumor and to identify markers with potential diagnostic and prognostic implications.

Methods

Targeted sequencing with a panel of 18 thyroid cancer-related genes was performed on 48 tissue samples from follicular thyroid adenoma (FTA), 32 follicular tumors of uncertain malignant potential (FT-UMP), 17 well-differentiated tumors of uncertain malignant potential (WDT-UMP) and 53 samples from follicular thyroid carcinoma (FTC). The correlation of mutation profiles and clinicopathological features and prognosis were also analyzed.

Results

We identified 95 nonsilent mutations spanning 14 genes. Specifically, TERT promoter (TERTp) mutations were exclusively detected in FTC. A total of 80% EIF1AX exon 2 mutations (4/5) and 75% TSHR mutations (3/4) occurred in FTA, whereas the rest of them occurred in FT-UMP. KRAS mutations and TP53 mutations were only presented in borderline or malignant tumors. H/N-RAS mutations were detected in all four subtypes, but were most commonly found in WDT-UMP (p = 0.031). All N-RAS mutations were located at codon 61. BRAF V600E and RET fusion were absent in the entire cohort. In FTC cases, EIF1AX mutations were all located at intron 5/exon 6 and correlated with advanced disease (p = 0.032). Both EIF1AX and TERTp mutations predicted shorter disease-free survival (p = 0.007, p = 0.024, respectively). Further analysis revealed that TERTp mutations were correlated with shorter disease-free survival in patients with minimally invasive /encapsulated angioinvasive FTC (p = 0.017), but not in those with widely invasive FTC (p = 0.297).

Conclusion

TERTp, EIF1AX, TSHR, H/N/K-RAS and TP53 mutations may have diagnostic or prognostic potential in follicular thyroid tumors. TERTp mutations may predict a poor outcome in patients with minimally invasive/encapsulated angioinvasive FTC.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features in Asian Practice: Perspectives for Surgical Pathology and Cytopathology

The introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was initiated and promoted by pathologists. Recent Asian studies added new knowledge to the existing literature to aid a better understanding of NIFTP. Our original data and the results of a meta-analysis suggest that the initial rate of NIFTP has been overestimated, averaging 9.1% (95% confidence interval [CI] 6.0-12.7%) of all papillary thyroid cancers worldwide. The incidence of NIFTP in the Asian population (1.6%, 95% CI 0.9-2.5%; 7 studies) is significantly lower than that reported in the non-Asian series (13.3%, 95% CI 9.0-18.3%; 18 studies). Such difference could be attributed to various perceptions of histological diagnostic thresholds, different nature of papillary thyroid carcinoma, and different approaches in the management of thyroid nodules. The active surveillance for indeterminate nodules and NIFTP, largely represented in the indeterminate cytologic categories, promoted by Japanese institutions establishes a new paradigm to reduce overtreatment of these patients. The lower prevalence of NIFTP in the Asian series indicates a low impact on the risk of malignancy in cytopathology, as it was demonstrated in our original multi-institutional cohort of thyroid nodules, and may predict a low impact on the performance of commercial molecular tests. Several Korean studies addressed the issue of BRAF mutation in NIFTP, which prompted the current refinement of the diagnostic criteria for NIFTP. Our survey of Asian pathologists found that the term NIFTP has not been universally adopted in the local practice. Endocrine pathologists must promote the new entity through provision of educational activities.

How to handle borderline/precursor thyroid tumors in management of patients with thyroid nodules

Thyroid carcinomas originating from follicular cells have the prognosis of heterogeneous diseases, but pathologists classify them all as malignant disease. Epidemiologists have issued a stern warning regarding over-diagnosis and overtreatment of patients with indolent thyroid tumors that cause no harm to the patients. Review of the literature revealed that there were several proposals of borderline/precursor tumors to some indolent thyroid carcinomas. Thyroid tumor of uncertain malignant potential (UMP) was first proposed by Williams for encapsulated follicular pattern thyroid tumors to solve problems due to observer variation. Rosai et al. proposed to rename papillary microcarcinoma (PMC) to papillary micro-tumor as the overwhelming majority of them are of no clinical significance. Liu et al. proposed well-differentiated tumor with uncertain behavior (WDT-UB) which covered WDT of UMP (WDT-UMP) and non-invasive encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC). The EFVPTC without invasion was renamed as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) by an international panel of pathologists. A new prognostic classification of thyroid tumors was proposed by Kakudo et al., in which extremely low risk tumors were grouped in a borderline tumors category. The borderline/precursor thyroid tumors included encapsulated tumors [capsular invasion only follicular carcinoma, encapsulated papillary carcinoma without invasion, WDT-UMP and follicular tumor of UMP (FT-UMP)] and non-encapsulated tumors (PMC). The UMP and NIFTP were incorporated in the 4th edition WHO classification of thyroid tumors as a new tumor entity in chapter 2-2A: other encapsulated follicular patterned thyroid tumors. Their behavior codes were decided to be 1 (borderline or uncertain behavior), and not 0 (benign), 2 (in situ carcinoma) or 3 (malignant). These borderline/precursor thyroid tumors are indolent tumors biologically and should be treated more conservatively than as previously recommended for thyroid follicular cell carcinomas [total thyroidectomy (TTX) followed by radio-active iodine (RAI) treatment] by western clinical guidelines.

Prevalence of BRAFV600E Mutation in Follicular Variant of Papillary Thyroid Carcinoma and Non-Invasive Follicular Tumor with Papillary-Like Nuclear Features (NIFTP) in a BRAFV600E Prevalent Area

BACKGROUND

BRAF^V600E mutation status and prevalence of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has not yet been reported in Korea. The aim of this study was to investigate the significance of the BRAF^V600E mutation in the follicular variant of papillary thyroid carcinoma (FVPTC) and to determine the prevalence of NIFTP in BRAF^V600E mutation-prevalent Korean patients.

METHODS

This study retrospectively analyzed 1,417 consecutive patients who underwent total thyroidectomy with routine prophylactic central lymph node dissection for papillary thyroid carcinoma (PTC). BRAF^V600E mutation analysis was performed routinely using multiplex polymerase chain reaction by applying dual priming oligonucleotide. Clinicopathological characteristics and ultrasonographic findings were compared between BRAF^V600E mutation-positive and -negative groups for FVPTC. Pathologists reviewed the pathology slides according to consensus diagnostic criteria for the encapsulated FVPTC and NIFTP.

RESULTS

The prevalence of the BRAF^V600E mutation in all subtypes of PTC was 61.0% (861/1,411). FVPTC presented a BRAF^V600E mutation rate of 27.3%. The FVPTC patients with BRAF^V600E mutation were older than those with no BRAF^V600E mutation (P = 0.021). The prevalence of NIFTP was 0.18% among all PTC patients (2/1,411) and the proportion of NIFTP among FVPTC was 9.1% (2/22).

CONCLUSION

The BRAF^V600E mutation is prevalent in Korean patients with FVPTC in a region with high frequency of the BRAF^V600E mutation and very low prevalence of NIFTP compared with that reported in western studies.

Clinical Characteristics of Subtypes of Follicular Variant Papillary Thyroid Carcinoma

BACKGROUND

Among follicular variant papillary thyroid carcinomas (FVPTCs), the noninvasive encapsulated subtype has an excellent prognosis. For this reason, reclassification of noninvasive encapsulated FVPTC (EFVPTC) as a new entity called "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) has been proposed, but controversy remains. To characterize noninvasive EFVPTC in an Asian population, the clinicopathologic features of each FVPTC subtype were compared in a Korean population.

METHODS

FVPTC patients (n = 142) who underwent thyroidectomy between 2009 and 2014, and whose tumor size was >1 cm, were included in the study. The surgical pathology of each patient was reevaluated by two independent expert pathologists.

RESULTS

The percentages of noninvasive and invasive EFVPTC and infiltrative FVPTC (IFVPTC) in the study were 30%, 31%, and 39%, respectively. There was no difference in preoperative cytological diagnosis or the extent of surgery between noninvasive and invasive EFVPTC. However, the proportion of Bethesda category IV was lower in IFVPTC (16%) than in noninvasive and invasive EFVPTC (35% and 36%, respectively). Therefore, thyroid lobectomy was more common in noninvasive or invasive EFVPTC (54% or 48%, respectively) than in IFVPTC (16%). Noninvasive EFVPTC showed lower multiplicity, extrathyroidal extension, and BRAF^V600E mutation frequency (three cases; 8%) than did invasive EFVPTC, but other pathological characteristics were similar. However, IFVPTC showed significant differences in tumor size, extrathyroidal extension, lymph node metastasis, Tumor Node Metastasis stage, and American Thyroid Association high-risk category compared with noninvasive and invasive EFVPTC. In the noninvasive EFVPTC group, there were six (14%) cases with multifocality and three (7%) cases with lymph node metastasis. However, only two cases with multifocality and one case with lymph node metastasis originated from noninvasive FVPTC, while the other cases were from coexisting conventional PTCs.

CONCLUSIONS

Noninvasive EFVPTC has favorable pathological features, but lymph node metastasis or BRAF^V600E mutations were observed in some patients. Therefore, in order for the distinction between noninvasive EFVPTC and invasive EFVPTC to have more clinical significance, the criteria for NIFTP need to be more strictly revised.

Preoperative Molecular Markers in Thyroid Nodules

The need for distinguishing benign from malignant thyroid nodules has led to the pursuit of differentiating molecular markers. The most common molecular tests in clinical use are Afirma^® Gene Expression Classifier (GEC) and Thyroseq^® V2. Despite the rapidly developing field of molecular markers, several limitations exist. These challenges include the recent introduction of the histopathological diagnosis "Non-Invasive Follicular Thyroid neoplasm with Papillary-like nuclear features", the correlation of genetic mutations within both benign and malignant pathologic diagnoses, the lack of follow-up of molecular marker negative nodules, and the cost-effectiveness of molecular markers. In this manuscript, we review the current published literature surrounding the diagnostic value of Afirma^® GEC and Thyroseq^® V2. Among Afirma^® GEC studies, sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) ranged from 75 to 100%, 5 to 53%, 13 to 100%, and 20 to 100%, respectively. Among Thyroseq^® V2 studies, Se, Sp, PPV, and NPV ranged from 40 to 100%, 56 to 93%, 13 to 90%, and 48 to 97%, respectively. We also discuss current challenges to Afirma^® GEC and Thyroseq^® V2 utility and clinical application, and preview the future directions of these rapidly developing technologies.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: a review for pathologists

The rising incidence of papillary thyroid carcinoma is linked in part to inclusion of noninvasive follicular variant of papillary thyroid carcinoma. Despite its designation as carcinoma, noninvasive follicular variant of papillary thyroid carcinoma appears to be exceptionally indolent, often over treated by current treatment practices. Additionally, criteria for diagnosis have historically been subjective and challenging. Recently, an international multidisciplinary collaborative group performed a clinicopathologic survey of such cases with extended follow-up and concluded based on the outcome data that a revision in nomenclature was warranted, proposing 'Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP).' This monograph is a synopsis and guide for pathologists on NIFTP and focuses on histologic features, including inclusion and exclusion criteria used to define NIFTP, as well as grossing guidelines, reporting practices, and potential diagnostic limitations.

C Cell and Follicular Epithelial Cell Precursor Lesions of the Thyroid

CONTEXT

- The identification of precursor or dysplastic lesions in the thyroid is difficult. Pathology of the C cell has been extensively studied, and the preneoplastic nature of C-cell hyperplasia in the setting of familial medullary thyroid carcinomas is well established. However, the distinction between neoplastic and physiologic/reactive C-cell hyperplasia remains a challenge. Unlike C cells, the existence of a precursor lesion of follicular cell-derived tumors is less well established, and a dysplastic or preneoplastic follicular lesion has not been well defined.

OBJECTIVE

- To discuss putative precursor lesions in the thyroid arising from C cells and follicular epithelial cells.

DATA SOURCES

- Data were obtained from a review of the pertinent peer-reviewed literature.

CONCLUSIONS

- Although the preneoplastic nature of C-cell hyperplasia in the setting of familial medullary thyroid carcinoma is well recognized, the preneoplastic nature/malignant potential of reactive/physiologic C-cell hyperplasia and its role in the development of sporadic, medullary thyroid carcinoma is still unclear. Current data suggest that benign follicular lesions may have malignant potential, and there may be a multifocal progression from benign to malignant. Atypical follicular lesions in the background of chronic lymphocytic thyroiditis may represent dysplastic or premalignant lesions.

Molecular correlates and rate of lymph node metastasis of non-invasive follicular thyroid neoplasm with papillary-like nuclear features and invasive follicular variant papillary thyroid carcinoma: the impact of rigid criteria to distinguish non-invasive follicular thyroid neoplasm with papillary-like nuclear features

Thyroid tumors formerly classified as non-invasive encapsulated follicular variant of papillary thyroid carcinoma were recently renamed 'non-invasive follicular thyroid neoplasm with papillary-like nuclear features'. The current study investigated the frequency of lymph node metastasis and mutational profile of encapsulated follicular variant in the setting of a clinical practice where central neck dissection was the standard of practice. We defined the impact of rigid diagnostic criteria by regrouping such tumors based on the complete absence of papillae or presence of ≤1% papillae. Of a total of 6,269 papillary thyroid carcinomas, 152 tumors fulfilled the criteria for encapsulated follicular variant. The results were stratified according to two different diagnostic cutoff criteria with respect to the extent of papillae. When the cutoff of 1% papillae was used, the rates of lymph node metastasis and BRAF^V600E mutation were 3% and 10% in non-invasive tumors and 9% and 4% in invasive tumors, respectively. Despite the lack of invasive growth, one patient with BRAF^V600E mutant-tumor displaying predominant follicular growth and subtle papillae developed a bone metastasis. When absence of papillary structure was applied as rigid diagnostic criteria, no BRAF^V600E mutation was found in all tumors. However, central lymph node micrometastasis still occurred in 3% of non-invasive tumors. Non-V600E BRAF and RAS mutations were detected in 4% and 47% of non-invasive tumors, respectively. Our findings suggest that non-invasive follicular thyroid neoplasm with papillary-like nuclear features should not be regarded as a benign thyroid neoplasm as it can present with lymph node micrometastasis and should not be diagnosed in the presence of even a single papillary structure. Our findings underscore the original American Thyroid Association recommendation that defined non-invasive encapsulated follicular variants as low risk thyroid cancers. Clinical surveillance similar to low risk differentiated thyroid cancers and capture of this diagnostic category by Cancer Registries should be considered.

The impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features on the performance of the Afirma gene expression classifier

BACKGROUND

A recent revision in thyroid tumor nomenclature has resulted in a change from a malignant diagnosis (noninvasive follicular variant of papillary thyroid carcinoma) to one that is nonmalignant (noninvasive follicular thyroid neoplasm with papillary-like nuclear features [NIFTP]). The objective of the current study was to evaluate the impact of this change on the performance of the Afirma gene expression classifier (GEC).

METHODS

The authors retrospectively analyzed consecutive thyroid fine-needle aspiration specimens with indeterminate diagnoses on which GEC was performed. Surgical pathology material was reviewed with the reclassification of nodules into NIFTP.

RESULTS

GEC testing was performed on 384 fine-needle aspiration specimens diagnosed as atypia of undetermined significance (AUS) (304 cases) and suspicious for a follicular neoplasm (SFN) (80 cases) and yielded a suspicious result in 152 of the AUS cases (50%) and 50 of the SFN cases (63%). Thyroidectomy was performed on 177 patients. After reclassifying NIFTP, the positive predictive value of GEC decreased from 42% (95% confidence interval [95% CI], 39%-45%) to 24% (95% CI, 22%-26%) in the AUS group and from 23% (95% CI, 19%-27%) to 13% (95% CI, 9%-18%) in the SFN group. Total thyroidectomy was performed more frequently than a partial thyroidectomy in patients with AUS with a suspicious GEC result compared with pre-GEC controls (68% vs 49%; P = .037).

CONCLUSIONS

Reclassification of NIFTP significantly decreases the positive predictive value of GEC in indeterminate thyroid nodules. Nevertheless, the majority of patients with indeterminate thyroid nodules with a suspicious GEC result in the study institution have undergone total thyroidectomy. This finding raises concerns over reliance on a suspicious GEC result by clinicians to justify total thyroidectomy. Cancer Cytopathol 2017;125:683-91. © 2017 American Cancer Society.

Clinicopathological features of thyroid cancer in the elderly compared to younger counterparts: single-center experience

PURPOSE

The incidence of thyroid cancer is increased in elderly patients. It tends to be larger and have more aggressive characteristics in these patients. Our aim was to compare features of thyroid carcinoma in geriatric and non-geriatric patients.

METHODS

In total, 933 patients with thyroid cancer were retrospectively reviewed. Thyroid functions, ultrasonography features of malignant nodules, cytological and histopathological findings and the rates of recurrence and persistence were compared in patients ≥65 and <65 years old.

RESULTS

There were 153 malignant foci in 109 (11.7%) patients ≥65 and 1185 malignant foci in 824 (88.3%) patients <65 years old. Mean nodule diameter was significantly higher in geriatric patients (p = 0.008). Most of the ultrasonographical features of malignant nodules were similar in two groups. Hypoechoic halo was observed in 16.4 and 28.6% of malignant nodules in geriatric and non-geriatric group, respectively (p = 0.034). There was no significant difference in cytological diagnosis. Histopathologically, tumor diameter, rates of microcarcinomas and incidentality were similar. Of all cancer types, 88.8% in geriatric and 93.9% in non-geriatric group were papillary thyroid cancer (p = 0.028). Hurthle cell cancer constituted 3.9 and 1.1% of carcinomas in geriatric and non-geriatric patients, respectively (p = 0.015); 2.0 and 0.2% of tumors in geriatric and non-geriatric group were anaplastic, respectively (p = 0.012). Capsular and vascular invasion, extrathyroidal extension, persistence and recurrence rates were similar.

CONCLUSIONS

Rates of anaplastic cancer and Hurthle cell cancer which is known to have worser prognosis among other differentiated thyroid cancers are increased in geriatric ages. Cytological evaluation of thyroid nodules should strongly be considered due to increased tendency for aggressive tumor types in these patients.

Outcome of Large Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features

BACKGROUND

In 2016, encapsulated follicular variant of papillary thyroid carcinoma without invasion was renamed "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) in order to reduce overtreatment of this indolent tumor. However, many endocrinologists remain uneasy about managing large (≥4 cm) NIFTP conservatively without radioactive iodine (RAI) therapy. The objectives of this study are to characterize the clinicopathologic characteristics and outcome of large NIFTP in order to assist therapeutic decision making.

METHODS

The pathology databases of four tertiary hospitals were searched for large (≥4 cm) NIFTP. Cases with separate foci of carcinoma were excluded. Seventy-nine cases fulfilled the inclusion criteria. Among them, 56 (71%) had at least two years of clinical follow-up (FU), and 49 (62%) had four or more years of FU. The clinicopathologic characteristics were reviewed and documented by four endocrine pathologists.

RESULTS

The median size of the NIFTP was 4.5 cm (range 4.0-8.0 cm). The entire capsule was sampled in 50 (63%) tumors, while in the remaining 29 (37%) cases, it was submitted representatively, with a median of 2.1 blocks per centimeter of tumor examined. Large NIFTP had a female preponderance with a male:female ratio of 1:1.8, and presented at a median age of 49 years. There were no lymph node metastases at diagnosis in any of the patients, and none of the patients (n = 25) in whom nodal tissue was available for microscopic examination had positive findings. Twenty-six (33%) underwent thyroid lobectomy alone, and 37 (47%) did not receive RAI ablation. No recurrence was observed in the entire cohort, including all 32 patients with two or more years of FU who did not receive RAI therapy (median FU: 6.7 years). Among patients with four or more years of FU, all 25 individuals without RAI therapy did not recur, with a median FU of 11.2 years. Patients with a larger tumor size tended to receive postoperative RAI ablation (p = 0.001).

CONCLUSIONS

Similar to their small counterparts, large NIFTP appear to have an extremely low risk of recurrence (zero in this cohort), even when treated conservatively without RAI therapy. Surgical treatment alone, including lobectomy, appears to be adequate for large NIFTP.

Nomenclature Revision for Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A Paradigm Shift to Reduce Overtreatment of Indolent Tumors

IMPORTANCE

Although growing evidence points to highly indolent behavior of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC), most patients with EFVPTC are treated as having conventional thyroid cancer.

OBJECTIVE

To evaluate clinical outcomes, refine diagnostic criteria, and develop a nomenclature that appropriately reflects the biological and clinical characteristics of EFVPTC.

DESIGN, SETTING, AND PARTICIPANTS

International, multidisciplinary, retrospective study of patients with thyroid nodules diagnosed as EFVPTC, including 109 patients with noninvasive EFVPTC observed for 10 to 26 years and 101 patients with invasive EFVPTC observed for 1 to 18 years. Review of digitized histologic slides collected at 13 sites in 5 countries by 24 thyroid pathologists from 7 countries. A series of teleconferences and a face-to-face conference were used to establish consensus diagnostic criteria and develop new nomenclature.

MAIN OUTCOMES AND MEASURES

Frequency of adverse outcomes, including death from disease, distant or locoregional metastases, and structural or biochemical recurrence, in patients with noninvasive and invasive EFVPTC diagnosed on the basis of a set of reproducible histopathologic criteria.

RESULTS

Consensus diagnostic criteria for EFVPTC were developed by 24 thyroid pathologists. All of the 109 patients with noninvasive EFVPTC (67 treated with only lobectomy, none received radioactive iodine ablation) were alive with no evidence of disease at final follow-up (median [range], 13 [10-26] years). An adverse event was seen in 12 of 101 (12%) of the cases of invasive EFVPTC, including 5 patients developing distant metastases, 2 of whom died of disease. Based on the outcome information for noninvasive EFVPTC, the name "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was adopted. A simplified diagnostic nuclear scoring scheme was developed and validated, yielding a sensitivity of 98.6% (95% CI, 96.3%-99.4%), specificity of 90.1% (95% CI, 86.0%-93.1%), and overall classification accuracy of 94.3% (95% CI, 92.1%-96.0%) for NIFTP.

CONCLUSIONS AND RELEVANCE

Thyroid tumors currently diagnosed as noninvasive EFVPTC have a very low risk of adverse outcome and should be termed NIFTP. This reclassification will affect a large population of patients worldwide and result in a significant reduction in psychological and clinical consequences associated with the diagnosis of cancer.

The Ethical Implications of the Reclassification of Noninvasive Follicular Variant Papillary Thyroid Carcinoma

BACKGROUND

Several studies have highlighted the lack of consensus in the diagnosis of follicular variant of papillary thyroid carcinoma (FVPTC). An international multidisciplinary panel to address the controversy was assembled at the annual meeting of the Endocrine Pathology Society in March of 2015, leading to the recent publication reclassifying encapsulated (or noninvasive) FVPTC (EFVPTC) as a benign neoplasm. Does this change in histologic taxonomy warrant a change in clinical practice, and how should it affect those who have been given this diagnosis in the past? We consider the financial and psychological impact of this reclassification and discuss the ethical, legal, and practical issues involved with sharing this information with the patients who are affected.

SUMMARY

The total direct and indirect cost of thyroid cancer surveillance in patients is significant. High levels of clinically relevant distress affect up to 43% of patients with papillary thyroid carcinoma, as estimated by the Distress Thermometer developed by the National Comprehensive Cancer Network for detecting distress in cancer patients. Although there are currently no legal opinions that establish a precedent for recontacting patients whose clinical status is altered by a change in nomenclature, the prudent course would be to attend to the requirements of medical ethics.

CONCLUSION

Informing patients with a previous diagnosis of EFVPTC that the disease has been reclassified as benign is expected to have a dramatic effect on their surveillance needs and to alleviate the psychological impact of living with a diagnosis of cancer. It is important to re-evaluate the pathologic slides of those patients at risk to ensure that the invasive nature of the tumor is comprehensively evaluated before notifying a patient of a change in diagnosis. The availability of the entire tumor for evaluation of the capsule may prove to be a challenge for a portion of the population at risk. We believe that it is the clinician's professional duty to make a sincere and reasonable effort to convey the information to the affected patients. We also believe that the cost savings with respect to the need for additional surgery, radioactive iodine, and rigorous surveillance associated with a misinterpretation of the biology of the diagnosis of EFVPTC in less experienced hands will likely more than offset the cost incurred in histologic review and patient notification.

Comparing Clinicopathologic and Radiographic Findings Between TT-UMP, Classical, and Non-Encapsulated Follicular Variants of Papillary Thyroid Carcinomas

Thyroid tumors of uncertain malignant potential (TT-UMP) comprise an accepted subgroup of follicular-patterned thyroid tumors for which benignancy or malignancy cannot be precisely assessed. We aimed to evaluate the demographic characteristics, ultrasound (US) findings, and cytological results of patients with TT-UMP and compare these findings to a classical variant of papillary thyroid carcinoma (CV-PTC) and non-encapsulated follicular variant of PTC (NEFV-PTC) patients; we also evaluated the immunohistochemical characteristics of patients with TT-UMP. Twenty-four patients with TT-UMP, 672 with CV-PTC, and 132 with NEFV-PTC were included in the study. Mean longitudinal nodule size and median nodule volume were higher in the TT-UMP group than in the CV-PTC and NEFV-PTC groups (p < 0.001 and p < 0.001 for CV-PTC; p < 0.001 and p = 0.008 for NEFV-PTC). The presence of halo and peripheral vascularization was observed more frequently in the TT-UMP group than in the CV-PTC group (p = 0.002 and p = 0.024). Benign and follicular neoplasm/suspicious for follicular neoplasm cytological results were higher in the TT-UMP group than in the CV-PTC group (p = 0.030 and p = 0.001). US findings were similar between TT-UMP and NEFV-PTC groups (all, p > 0.05). However, none of the patients with TT-UMP were called malignant; 105 patients (31.2 %) of CV-PTC and 11 patients (9.5 %) of NEFV-PTC (infiltrative FV) were classified as malignant cytologically. Tumor size was higher in the TT-UMP group than in the CV-PTC and NEFV-PTC groups (p < 0.001 and p = 0.006). In the TT-UMP group, positive expression of HBME-1, CK-19, and Gal-3 was found in 50, 33.3, and 25 % of patients, respectively. This study demonstrated that none of the TT-UMP patients were evaluated as malignant in preoperative cytology. However, patients with TT-UMP had higher nodule and tumor sizes than CV-PTC and NEFV-PTC patients; US features were similar between NEFV-PTC and TT-UMP patients.

Noninvasive Follicular Variant of Papillary Thyroid Carcinoma and the Afirma Gene-Expression Classifier

BACKGROUND

It is now recognized that noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) is a distinct subset of FVPTC with an exceedingly indolent clinical course. The Afirma gene-expression classifier (GEC) helps guide clinicians in the management of thyroid nodules with indeterminate fine-needle aspiration (FNA) results. Thyroid surgery is recommended for nodules with a suspicious Afirma result, whereas observation is deemed reasonable for most nodules with a benign result. The aim of this study was to confirm that the Afirma test detects NFVPTCs and to determine how many carcinomas detected by the Afirma GEC represent NFVPTCs.

METHODS

From a database of 249 FNAs sent for Afirma testing between January 2012 and October 2014, a search was conducted for cases with a preceding FNA diagnosis of atypia/follicular lesion of undetermined significance (AUS/FLUS) or suspicious for a follicular neoplasm (SFN), a suspicious Afirma result, and a corresponding resection specimen reviewed at Brigham and Women's Hospital. The diagnoses of the prior FNAs and subsequent resection specimens were recorded. Slides for all resection specimens with a diagnosis of FVPTC were reviewed to identify NFVPTCs.

RESULTS

Sixty-three cases met the inclusion criteria. The preceding FNA diagnosis was AUS/FLUS in 34 (54%) cases and SFN in 29 (46%) cases. The surgical resection specimen demonstrated 16 (25%) FVPTCs, five (8%) follicular thyroid carcinomas, one (2%) classical type PTC, and 41 (65%) benign tumors/nodules. Of the 16 FVPTCs, 14 (88%) were NFVPTCs. Thus, NFVPTCs accounted for 64% of the carcinomas in the cohort.

CONCLUSION

These results indicate that the Afirma GEC detects NFVPTCs and that many of the carcinomas detected by Afirma are NFVPTCs. While all care should be individualized and include clinical and sonographic assessment, these results suggest lobectomy as opposed to total thyroidectomy should be considered for nodules with a preceding AUS/FLUS or SFN on cytology and a suspicious Afirma result.

Stromal modulation and its role in the diagnosis of papillary patterned thyroid lesions

The papillary patterned lesion of thyroid may be challenging with many diagnostic pitfalls. Tumor stroma plays an important part in the determination of the tumor phenotype. CD34 is thought to be involved in the modulation of cell adhesion and signal transduction as CD34(+) fibrocytes are potent antigen-presenting cells. Smooth muscle actin (SMA) positivity could be diagnostic for fibroblast activation during tumorigenesis. We aimed to examine the expression of CD34 and alphaSMA in the stroma of papillary thyroid hyperplasia, papillary thyroid carcinoma and papillary tumors of uncertain malignant potential in order to elucidate their possible differential distribution and roles. A total number of 54 cases with papillary thyroid lesions were studied by routine HandE staining, CD34 and ASMA immunostaining. ASMA was not expressed in benign papillary hyperplastic lesions while it was expressed in papillary carcinoma, indicating that tumors have modulated stroma. Although the stroma was not well developed in papillary lesions with equivocal features of uncertain potentiality, CD34 was notable in such cases with higher incidence in malignant cases. So ASMA as well as CD34 could predict neoplastic behavior, pointing to the importance of the stromal role. Differences between groups suggest that the presence of CD34 + stromal cells is an early event in carcinogensis and is associated with neoplasia, however ASMA+ cells are more likely to be associated with malignant behavior and metastatic potential adding additional tools to the light microscopic picture helping in diagnosis of problematic cases with HandE.

Defining the value of CD56, CK19, Galectin 3 and HBME-1 in diagnosis of follicular cell derived lesions of thyroid with systematic review of literature

BACKGROUND

Nodular follicular lesions of thyroid gland comprise benign and malignant neoplasms, as well as some forms of hyperplasia. "Follicular" refers to origin of cells and in the same time to growth pattern - building follicles. Nodular follicular thyroid lesions have in common many morphological features, therefore attempts were made to define additional criteria for distinction between follicular adenoma, follicular carcinoma and follicular variant of papillary carcinoma. Increasing number of immunohistochemical markers is in the continual process of evaluation.

METHODS

Tissue microarrays incorporating, total 201 cases, out of which 122 malignant and 79 benign follicular lesions, including neoplastic and non-neoplastic, were constructed and immunostained with antibodies to CD56, CK19, Galectin-3, HBME-1. Tissue cores were exclusively being acquired from tumour/lesion on interface with normal thyroid tissue. A systematic review of literature was done for period from the year 2001 to present time.

RESULTS

All analysed markers may make a difference between benign lesions/tumours from differentiated thyroid carcinomas (p = <0.01, for all markers). Expression of all markers is significantly higher in papillary carcinoma than in follicular adenoma (p < 0.01). Statistically significant difference in expression of Galectin-3 and CD56 between follicular carcinoma and follicular adenoma was registered (p = 0.043; p = 0.028, respectively). The only marker which expression showed statistically significant difference between adenoma and carcinoma of Hurthle cells was Galectin 3 (p = 0.041). CK19 and HBME-1 were significantly expressed more in papillary carcinoma as compared to follicular carcinoma.

CONCLUSION

Galectin 3 is most sensitive marker for malignancy, while loss of expression of CD56 is very specific for malignancy. Expected co-expression for combination of markers in diagnosis of follicular lesions decreases sensitivity and increases specificity for malignancy.

Impact of reclassifying noninvasive follicular variant of papillary thyroid carcinoma on the risk of malignancy in The Bethesda System for Reporting Thyroid Cytopathology

BACKGROUND

Recent discussions have focused on redefining noninvasive follicular variant of papillary thyroid carcinoma (NI-FVPTC) as a neoplasm rather than a carcinoma. This study assesses the potential impact of such a reclassification on the implied risk of malignancy (ROM) for the diagnostic categories of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC).

METHODS

The study consisted of consecutive fine-needle aspiration biopsy (FNAB) cases collected between January 1, 2013 and June 30, 2014 from 5 academic institutions. Demographic information, cytology diagnoses, and surgical pathology follow-up were recorded. The ROM was calculated with and without NI-FVPTC and was presented as a range: all cases (ie, overall risk of malignancy [OROM]) versus those with surgical follow-up only.

RESULTS

The FNAB cohort consisted of 6943 thyroid nodules representing 5179 women and 1409 men with an average age of 54 years (range, 9-94 years). The combined average ROM and OROM for the diagnostic categories of TBSRTC were as follows: nondiagnostic, 4.4% to 25.3%; benign, 0.9% to 9.3%; atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 12.1% to 31.2%; follicular neoplasm (FN), 21.8% to 33.2%; suspicious for malignancy (SM), 62.1% to 82.6%; and malignant, 75.9% to 99.1%. The impact of reclassifying NI-FVPTC on the ROM and OROM was most pronounced and statistically significant in the 3 indeterminate categories: the AUS/FLUS category had a decrease of 5.2% to 13.6%, the FN category had a decrease of 9.9% to 15.1%, and the SM category had a decrease of 17.6% to 23.4% (P < .05), whereas the benign and malignant categories had decreases of 0.3% to 3.5% and 2.5% to 3.3%, respectfully. The trend of the effect on the ROM and OROM was similar for all 5 institutions.

CONCLUSIONS

The results from this multi-institutional cohort indicate that the reclassification of NI-FVPTC will have a significant impact on the ROM for the 3 indeterminate categories of TBSRTC.

Cyclin D1 in well differentiated thyroid tumour of uncertain malignant potential

Background

Encapsulated follicular tumours with equivocal papillary thyroid carcinoma (PTC) type nuclear features continue to remain a challenge despite the recent attempts to classify these borderline lesions. The term ‘well differentiated tumour of uncertain malignant potential (WDT-UMP)’ was introduced to classify these tumours. The present study aimed to evaluate the role of a cell cycle regulator like cyclin D1 in these tumours along with assessment of other well established PTC markers like galectin-3, HBME-1, CK19.

Methods

Thirteen cases of metastatic PTC, papillary microcarcinoma and follicular variant of PTC (FVPTC) were identified from a histological review of 510 cases. In addition, 13 cases of a subset of follicular adenomatoid nodules with focal areas showing nuclear features characteristic of PTC, identified as WDT-UMP, were also analyzed. Immunohistochemical analysis of galectin-3, HBME-1, CK19 and the proliferation markers Ki67 and cyclin D1 was performed. Lesions were analyzed for cyclin D1 gene amplification by fluorescent in-situ hybridization.

Results

All WDT-UMP lesions showed immunolabelling of cyclin D1, Ki67; 11/ 13 cases showed immunolabelling of CK19; 10/13 cases showed immunolabelling of HBME-1 and 4/13 cases showed immunolabelling of galectin-3. Surrounding benign adenomatoid areas showed no to faint focal staining in all thirteen cases of cyclin D1, HBME-1 and galectin-3. A low rate of cyclin D1 gene amplification was identified in a significant proportion of cells in the WDT-UMP lesions as compared to surrounding benign adenomatoid areas.

Conclusions

Increased expression of cyclin D1 and amplification of its gene along with immunolabelling of HBME-1 in WDT-UMP lesions showing cytological features of papillary thyroid carcinoma within follicular adenomatoid nodules suggest that these areas could correspond to a precursor lesion of follicular variant of PTC. Overexpression of cyclin D1, associated with the amplification of the gene suggests that these WDT-UMP lesions are an intermediate between the benign and malignant groups making this group of lesions a reliable precursor of FVPTC.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1851820807142117

Diagnostic criteria of well differentiated thyroid tumor of uncertain malignant potential; a histomorphological and immunohistochemical appraisal

BACKGROUND

Well differentiated thyroid tumor of uncertain malignant potential (WDT-UMP) represents a true "gray zone" of "follicular patterned" thyroid lesions, that needs to be characterized in order to outright the diagnosis of carcinoma and avoid unnecessary aggressive treatment.

AIM

To emphasize on the histomorphological criteria for more accurate diagnosis of WDT-UMP. Also to compare the immunohistochemical expression of CK19 of WDT-UMP versus adenoma and papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

The study included 60 thyroid specimens; 18 WDT-UMPs, 24 PTC (18 classic variant and 6 follicular variants) and 18 benign thyroid lesions (8 adenoma, 6 Hashimoto's thyroiditis and 4 hyperplastic nodules). H&E stained sections were assessed according to the published major and minor criteria of malignancy in the thyroid. CK 19 immunostaining was examined and evaluated according to the proportion and intensity scores.

RESULTS

We could detect the absence of nuclear inclusions, presence of characteristic nuclear groove, nuclear clearing, ovoid nuclei, nuclear crowdness, nuclear enlargement and pleomorphism as important reliable features for diagnosis of WDT-UMP with p value (<0.0001 for each). WDT-UMP showed moderate to strong CK 19 immunostaining with proportion scores 3 and 4; an intermediate expression profile; higher than adenoma and less than papillary carcinoma (p<0.0001).

CONCLUSION

The constellations of both major and minor criteria of malignancy are important clues for WDT-UMP diagnosis which could be ascertained by CK 19 immunostaining.

Follicular-patterned afflictions of the thyroid gland: reappraisal of the most discussed entity in endocrine pathology

The past 25 years has seen a marked increase in our understanding of thyroid neoplasia, from the interrelationship with radiation exposure, the definition of variants of papillary carcinoma, to the application of molecular biology techniques to capture a more basic definition of tumor development, diagnosis, and prognostic implications. No other group of thyroid tumors has been studied as much as those with follicular pattern. In this review, we present a reappraisal of these controversial lesions in light of the issues with the diagnostic problems and classification schemes of follicular thyroid lesions, with emphasis on the progress made in the past quarter century and a focus on the current persistent controversies.

Introducing the reporting system for thyroid fine-needle aspiration cytology according to the new guidelines of the Japan Thyroid Association

The Japan Thyroid Association (JTA) recently published new guidelines for clinical management of thyroid nodules. This paper introduces their diagnostic system for reporting thyroid fine-needle aspiration cytology. There are two points where the new reporting system that differs from existing internationally-accepted ones. The first is the subclassification of the so-called indeterminate category, which is divided into 'follicular neoplasm' and 'others'. The second is the subclassification of follicular neoplasm into 'favor benign', 'borderline' and 'favor malignant'. It is characterized by self-explanatory terminologies as to histological type and probability of malignancy to establish further risk stratification as well as to facilitate communication between clinicians and cytopathologists. The different treatment strategies adopted for thyroid nodules is deeply influenced by the particular diagnostic system used for thyroid cytology. In Western countries all patients with follicular neoplasms are advised to have immediate diagnostic surgery while patients in Japan often undergo further risk stratification without immediate surgery. The JTA diagnostic system of reporting thyroid cytology is designed for further risk stratification of patients with indeterminate cytology. If a surgeon applies diagnostic lobectomy to all patients with follicular neoplasm unselectively, this subclassification of follicular neoplasm has no practical meaning and is unnecessary. Cytological risk stratification of follicular neoplasms is optional and cytopathologists can choose either a simple 6-tier system without stratification of follicular neoplasm or a complicated 8-tier system depending on their experience in thyroid cytology and clinical management.

HBME-1 expression in hyalinizing trabecular tumours of the thyroid gland

AIMS

Hyalinizing trabecular tumour (HTT) is a rare thyroid neoplasm with a trabecular growth pattern, marked intratrabecular hyalinization and nuclear features of papillary thyroid carcinoma (PTC). Immunohistochemical HBME-1 expression was reported recently in PTC, but not in HTT. To clarify further the value of HBME-1 expression as a tool in differential diagnosis, we investigated the immunophenotype of HTT.

METHODS AND RESULTS

Eight HTT diagnosed from 1997 to 2012 were reviewed on H&E-stained tissue sections and analysed for HBME-1, galectin-3, CK19 and Ki67 expression by immunohistochemistry. Three of eight HTTs (37.5%) were HBME-1 positive, with staining of tumour cells as well as of intratrabecular hyaline matrix material. All cases were CK19 negative. Galectin-3 was expressed weakly in four of eight cases (50%). Five of eight cases (62.5%) showed weak-to-moderate cytoplasmic Ki67 positivity.

CONCLUSIONS

Immunohistochemical HBME-1 expression is present in HTT and may not serve as a reliable marker in differentiating HTT from PTC. The HBME-1 positivity of the hyaline matrix suggests that this material is partly of cytoplasmic origin.

Loss of heterozygosity and methylation of multiple tumor suppressor genes on chromosome 3 in hepatocellular carcinoma

BACKGROUND

Genetic and epigenetic alterations are the two key mechanisms in the development of hepatocellular carcinoma (HCC). However, how they contribute to hepatocarcinogenesis and the correlation between them has not been fully elucidated.

METHODS

A total of 48 paired HCCs and noncancerous tissues were used to detect loss of heterozygosity (LOH) and the methylation profiles of five tumor suppressor genes (RASSF1A, BLU, FHIT, CRBP1, and HLTF) on chromosome 3 by using polymerase chain reaction (PCR) and methylation-specific PCR. Gene expression was analyzed by immunohistochemistry and reverse transcription (RT)-PCR.

RESULTS

Sixteen of 48 (33.3 %) HCCs had LOH on at least one locus on chromosome 3, and two smallest common deleted regions (3p22.3-24.3 and 3p12.3-14.2) were identified. RASSF1A, BLU, and FHIT showed very high frequencies of methylation in HCCs (100, 81.3, and 64.6 %, respectively) and noncancerous tissues, but not in liver tissues from control patients. Well-differentiated HCCs showed high methylation frequencies of these genes but very low frequencies of LOH. Furthermore, BLU methylation was associated with an increased level of alpha-fetoprotein, and FHIT methylation was inversely correlated with HCC recurrence. In comparison, CRBP1 showed moderate frequencies of methylation, while HLTF showed low frequencies of methylation, and CRBP1 methylation occurred mainly in elderly patients. Treatment with 5-aza-2'-deoxycytidine demethylated at least one of these genes and restored their expression in a DNA methylation-dependent or -independent manner.

CONCLUSIONS

Hypermethylation of RASSF1A, BLU, and FHIT is a common and very early event in hepatocarcinogenesis; CRBP1 methylation may also be involved in the later stage. Although LOH was not too frequent on chromosome 3, it may play a role as another mechanism in hepatocarcinogenesis.