Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): Update and Diagnostic Considerations-a Review

Are we ready to bridge classification systems? A comprehensive review of different reporting systems in thyroid cytology

The evaluation of thyroid lesions is common in the daily practice of cytology. While the majority of thyroid nodules are benign, in recent decades, there has been increased detection of small and well-differentiated thyroid cancers. Combining ultrasound evaluation with fine-needle aspiration cytology (FNAC) is extremely useful in the management of thyroid nodules. Furthermore, the adoption of specific terminology, introduced by different thyroid reporting systems, has helped effectively communicate thyroid FNAC diagnoses in a clear and understandable way. In 1996, the Papanicolaou Society thyroid cytological classification was introduced. This was followed in 2005 by the first Japanese and then in 2007 by the Bethesda System for Reporting Thyroid Cytopathology, which subsequently underwent two revisions. Other international thyroid terminology classifications include the British, Italian, Australasian and other Japanese cytology systems. This review covers similarities and differences among these cytology classification systems and highlights key points that unify these varied approaches to reporting thyroid FNAC diagnoses.

Case report & review: Bilateral NIFTP harboring concomitant HRAS and KRAS mutation: Report of an unusual case and literature review

Diagnosis and treatment of thyroid disease are affected by the wide range of thyroid cancer subtypes and their varying degrees of aggressiveness. To better describe the indolent nature of thyroid neoplasms previously classified as noninvasive follicular variant of papillary thyroid carcinoma (NI-FVPTC), the Endocrine Pathology Society working group has recently coined the term "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP). The purpose of this nomenclature change is to avoid patients the distress of cancer diagnosis and to decrease the overtreatment of thyroid nodules with a RAS-LIKE molecular profile similar to follicular adenoma. Consequently, the reclassification has a significant impact on thyroid nodule clinical care as well as histopathologic and cytopathologic diagnosis. This paper will focus on a unique case of Bilateral NIFTP harboring concomitant HRAS and KRAS mutation; we will also review the background, molecular features, and clinical implications of NIFTP as well as the factors behind the nomenclature update. It also seemed helpful to emphasize the impact of NIFTP on clinical practice to avoid overtreating nodules that could be safely managed with lobectomy alone. Actually, despite the diagnosis is postsurgery, a comprehensive preoperative evaluation may raise a suspicion of NIFTP and suggest a more careful plan for treatment. Here, we present a unique case of bilateral NIFTP after total thyroidectomy; subsequent molecular analysis revealed that the patient's right nodule harbored an isolated p.(Q61K) HRAS mutation, while the left a p.(Q61K) KRAS mutation. To the best of our knowledge, this is the first case report of this nature. The existence of simultaneous mutations highlights the occurrence of intratumoral heterogeneity (ITH) also in the context of FVPTC, which requires comprehensive investigation. The available information shows that NIFTP, identified in accordance with stringent inclusion and exclusion criteria, exhibits a very latent clinical behavior even in the face of conservative lobectomy, lacking of radioactive iodine therapy. However, it cannot be regarded as a benign lesion because there is a small but significant incidence of adverse events, such as lymph nodes and distant metastases. Currently, NIFTP can only be suspected before surgery: several efforts could be explored to identify key molecular, cytological, and ultrasonographic traits that may be helpful in raising the possibility of NIFTP in the preoperative context. Additionally, our discovery of simultaneous mutations within the same lesion strengthens the evidence of ITH even in FVPTC. Although the extent and biological impact of this phenomenon in NIFTP are still debated, a deeper understanding is essential to ensure appropriate clinical management.

Thyroid Fine-Needle Aspiration: The Current and Future Landscape of Cytopathology

Thyroid cytology is a rapidly evolving field that has seen significant advances in recent years. Its main goal is to accurately diagnose thyroid nodules, differentiate between benign and malignant lesions, and risk stratify nodules when a definitive diagnosis is not possible. The current landscape of thyroid cytology includes the use of fine-needle aspiration for the diagnosis of thyroid nodules with the use of uniform, tiered reporting systems such as the Bethesda System for Reporting Thyroid Cytopathology. In recent years, molecular testing has emerged as a reliable preoperative diagnostic tool that stratifies patients into different risk categories (low, intermediate, or high) with varying probabilities of malignancy and helps guide patient treatment.

Nodal metastasis in noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

The term noninvasive tumor with a follicular growth pattern and nuclear features of papillary thyroid cancer (NIFTP) is used to describe a tumor currently considered as a pre-malignant lesion for which a conservative therapeutic approach (i.e., lobectomy without radioiodine therapy) is strongly suggested. However, some patients with NIFTP and loco-regional or distant metastases have been already reported. We present an adult male patient with a final histological diagnosis of NIFTP and lymph node metastasis noted at post-therapy whole-body scintigraphy performed some days after radioiodine therapy.

Prevalence, Molecular Landscape, and Clinical Impact of DICER1 and DGCR8 Mutated Follicular-Patterned Thyroid Nodules

BACKGROUND

Mutations in micro-RNA (miRNA) regulators DICER1 and DGCR8 have recently been uncovered, revealing a potential novel mechanism driving thyroid tumor development. However, the true frequency of these hotspot mutations in follicular-patterned thyroid tumors (FTs) and their relation to established driver gene events remain elusive.

METHODS

A total of 440 FTs from 2 institutions were interrogated for DICER1, DGCR8, and RAS family hotspot mutations using Sanger sequencing. Whole-exome sequencing was also performed to identify additional driver gene aberrations in DICER1/DGCR8-mutant cases. Subsets of cases were further analyzed using miRNA expression profiling, and key dysregulated miRNAs were validated as markers of DICER1 mutations using quantitative RT-PCR analysis. The Cancer Genome Atlas (TCGA) database was also probed for DICER1/DGCR8 mutations and miRNA dysregulation.

RESULTS

Fourteen (3.2%) and 4 (1%) FTs harbored DICER1 and DGCR8 hotspot mutations, respectively, in the combined cohort, and no cases with normal tissue available were found to exhibit a constitutional variant. Two DGCR8-mutant cases also harbored oncogenic RAS mutations. Whole-exome sequencing analysis did not identify additional driver gene events in DICER1/DGCR8-positive cases. Comprehensive miRNA expression profiling revealed a unique pattern of dysregulated miRNAs in DICER1/DGCR8-mutant cases compared with wild-type lesions. Moreover, DICER1-mutant cases showed a remarkable reduction of 5' arm miRNAs, findings corroborated in the TCGA cohort.

CONCLUSION

DICER1 and DGCR8 hotspot mutations are rare in unselected cohorts of FTs, and mutated cases exhibit a specific miRNA profile. Although DGCR8 mutations may coexist with established RAS gene alterations, FTs with DICER1 variants were devoid of other driver gene events.

Identification of NIFTP-Specific mRNA Markers for Reliable Molecular Diagnosis of Thyroid Tumors

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a low-risk thyroid tumor with a favorable prognosis. Nonetheless, differentiating NIFTP from other thyroid tumors remains challenging, necessitating reliable diagnostic markers. This study is aimed at discovering NIFTP-specific mRNA markers through RNA sequencing analysis of thyroid tumor tissues. We performed mRNA expression profiling for 74 fresh frozen thyroid tissue samples, including NIFTP and benign and malignant follicular-cell-derived tumors. NIFTP/malignant tumors showed 255 downregulated genes and 737 upregulated genes compared to benign tumors. Venn diagram analysis revealed 19 significantly upregulated and 7 downregulated mRNAs in NIFTP. Akaike information criterion analysis allowed us to select OCLN, ZNF423, LYG1, and AQP5 mRNA markers. We subsequently developed a predictive model based on logistic regression analysis using these four mRNAs, which we validated in independent samples (n = 90) using a qRT-PCR assay. This model demonstrated high accuracy in predicting NIFTP in discovery dataset (AUC (area under the receiver operating characteristic) = 0.960) and the validation dataset (AUC = 0.757). Our results suggest that OCLN, ZNF423, LYG1, and AQP5 mRNA markers might serve as reliable molecular markers for identifying NIFTP among other thyroid tumors, ultimately aiding in accurate diagnosis and management of NIFTP patients.

Clinical and Sonographic Features of Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features: A Retrospective Study

ABSTRACT

This study was designed to investigate the clinical and sonographic features of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTPs) as compared with classical papillary thyroid carcinoma (cPTC), follicular adenoma (FA), and follicular thyroid carcinoma (FTC). A total of 178 patients were enrolled in this study. The clinical characteristics and sonographic features of thyroid nodules were compared between NIFTP and cPTC or FA/FTC. All nodules were reclassified according to the Thyroid Ultrasound Imaging Reporting and Data System and American Thyroid Association guidelines classification. The mean size of NIFTP was 29.91 ± 14.71 mm, which was larger than that of cPTC ( P = 0.000). Significant difference was found in lymph node metastases between NIFTP and cPTC ( P = 0.000). Most NIFTPs showed solid composition, hypoechoic echogenicity, smooth margin, wider than tall shape, none echogenic foci, absence of halo, and perinodular vascularity, which were similar with FA and FTC. Compared with NIFTP, hypoechoic and very hypoechoic, taller than wide, irregular margin, punctate echogenic foci, absence of halo, and low vascularity were more commonly observed in cPTC. There were statistical differences both in American College of Radiology Thyroid Ultrasound Imaging Reporting and Data System and in American Thyroid Association classification between NIFTP and cPTC ( P < 0.05), but there were no significant differences between NIFTP and FTC/FA ( P > 0.05). The ultrasonographic characteristics of NIFTP were obviously different from cPTC but overlapped with FTC and FA. Ultrasound could help increase preoperative attention of NIFTP in an appropriate clinical setting, which may lead to a more conservative treatment approach.

The Impact of the 2022 WHO Classification of Thyroid Neoplasms on Everyday Practice of Cytopathology

This review outlines how the alterations in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors of the thyroid gland are likely to impact thyroid cytopathology. It is important to note that WHO subclassifies thyroid tumors into several new categories based on increased comprehension of the cell of origin, pathologic features (including cytopathology), molecular classification, and biological behavior. The 3rd edition of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) will debut in the near future and will include changes in diagnostic category designations. The changes in the 5th edition of the WHO will in some instances subtly, and in other instances significantly, impact the cytological diagnoses. Moreover, these changes will also affect other thyroid FNA classification schemes used internationally for classifying thyroid FNA specimens.

Effect of non-invasive follicular thyroid neoplasm with papillary-like features (NIFTP) terminology on surgical management concepts

BACKGROUND

Despite the strict diagnostic criteria recently proposed for non-invasive follicular thyroid neoplasm with papillary-like features (NIFTP), its incidence is still unknown. Employing a retrospective analysis of the follicular variant of papillary thyroid carcinoma (FVPTC), we investigated the diagnosis, prevalence and postoperative course of NIFTP.

METHODS

We examined retrospectively the records of 112 patients who had undergone thyroid surgery and had a postoperative diagnosis of FVPTC at our hospital from 2010 to 2021. All clinical, radiologic, and pathologic features were evaluated.

RESULTS

Only 34 (27.9%) patients met the strict pathologic criteria for NIFTP; 11 cases having been diagnosed as NIFTP initially and 23 after re-evaluation of histopathologic slides. None of the 11 NIFTP patients underwent a 2-stage operation, in contrast to 10 (29.4%) patients initially diagnosed as FVPTC who had a completion thyroidectomy after the initial hemithyroidectomy. The median follow-up was 14.5 (ranging from 0 to 78) months. None of the cases developed a recurrence.

CONCLUSION

To avoid unnecessary treatment or the follow-up advised for papillary thyroid carcinoma, clinicians and pathologists should be familiar with the terminology and the corresponding diagnostic criteria for NIFTP and their impact on management.

What you see might not be what you get: Analysis of 15 prospective cases of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

Introduction

Noninvasive follicular thyroid neoplasm with papillary-like nuclear (NIFTP) is a new entity. No previous study reported prospective cases, outlining using many quantitative and qualitative variables.

Methods

Retrospective analysis of all (15) prospective NIFTP cases diagnosed between 2017 and 2021 at our institution. Statistical quantitative analysis outlined demographic, history, ultrasound, histopathology and treatment characteristics. Qualitative analysis examined the cases, with details provided on three cases to highlight the different possible presentations and configurations.

Results

Mean age was 41.5 ± 9.91 years, 73.3% were females, and mean BMI was 29.49 ± 5.74 kg/m². About 87% patients were symptomatic; 86.6% had neck swelling. Ultrasound (US) showed multiple nodules in 71.4% of cases. Fine-needle aspiration cytology (FNAC) showed that follicular lesion of undetermined significance (42.8%) was most common, followed by benign nodule (21.3%). Using the Bethesda System for Reporting Thyroid Cytopathology, 7 cases were category III, 3 category IV, 3 category II, and 1 category I. 60% of patients underwent total thyroidectomy. All cases were diagnosed postoperatively, 2 patients had additional papillary microcarcinoma. In 3 cases, the NIFTP site in the histopathology of resected specimen was different than the US-recommended site of the FNAC.

Conclusion

We found discrepancies in the site and diagnosis of the preoperative US recommendation for the FNAC vs the postoperative histopathology of the specimen. These suggest that NIFTP might be incidentally and postoperatively diagnosed, irrespective of US or FNAC findings, hence its ‘true’ incidence might remain underestimated. As NIFTP cases higher BMI, Future research could predict preoperative diagnosis of NIFTP and explore associations with BMI.

•

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is follicular type of papillary carcinoma

•

NIFTP is postoperative diagnosis. Correlation of clinical, imaging, cytological and post-operative histopathology is needed

•

Site and diagnosis of suspected NIFTP on US-guided FNAC and histopathology after resection requires more research

•

Preoperative diagnosis of NIFTP requires more studies. Until guidelines are available, regular follow up should be done

Hyalinizing trabecular tumor: Cytologic, histologic and molecular features and diagnostic considerations

Hyalinizing trabecular tumors are a follicular origin neoplasm of the thyroid that usually present as an asymptomatic, well circumscribed, solitary mass. However, diagnosis of a hyalinizing trabecular tumor may be challenging especially on fine needle aspiration cytology and requires careful examination of the specimen to rule out potential mimickers such as papillary thyroid carcinoma, medullary thyroid carcinoma, paraganglioma, other follicular patterned neoplasms, intrathyroidal parathyroid tissue, and metastatic disease. We will review the cytologic, histologic and molecular features of hyalinizing trabecular tumors that aid in distinction from these mimickers with overlapping morphologic features and help ensure proper diagnosis for appropriate management.

Can Cytologic and Sonographic Features Help Prevent Overtreatment of Bethesda V Thyroid Nodules?

BACKGROUND

Although nearly half of thyroid nodules with Bethesda V cytology (suspicious for malignancy) may be benign or harbor low-grade neoplasms that can be sufficiently treated with lobectomy, many patients with Bethesda V cytology continue to be treated with total thyroidectomy. The objectives of this study were to establish whether cytomorphologic and ultrasonographic features can determine appropriate surgery for thyroid nodules with Bethesda V cytology and how often patients are overtreated with total instead of partial thyroidectomy.

METHODS

Utilizing a 10-y prospective database starting January 1, 2004, cytomorphologic and ultrasonographic features of thyroid nodules with Bethesda V cytology were reviewed. Overtreatment was defined as total thyroidectomy when histopathology revealed benign nodule, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) or a unilateral < 4 cm low risk cancer.

RESULTS

Sixty-three patients were included in the study. Seventeen (27%) had benign, 14 (22%) NIFTP, and 32 (51%) malignant nodules. On cytology, nuclear pseudoinclusions, and on ultrasound, taller-than-wide configuration, were more common in malignant than benign or NIFTP nodules. Among 56 patients who underwent total thyroidectomy, 14 and 11 had a benign or NIFTP nodule, respectively, and 13 had a unilateral < 4 cm low risk cancer, suggesting that 68% (38/56) were overtreated.

CONCLUSIONS

Total thyroidectomy for Bethesda V thyroid nodules may result in overtreatment in more than half of the patients. Although certain cytomorphologic and ultarsonographic features may be helpful in determining appropriate surgery for Bethesda V thyroid nodules, additional characteristics are needed to reduce overtreatment of these nodules.

Effect of the Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features (NIFTP) Nomenclature Revision on Indian Thyroid Fine-Needle Aspiration Practice

OBJECTIVES

To analyze risk of malignancy (ROM) in Bethesda categories (BCs) and the impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification on malignancy risk and surgical outcome.

METHODS

In this retrospective study based on fine-needle aspiration samples with histologic follow-up, ROM was analyzed in BCs. Possible cases of NIFTP were reviewed, followed by the analysis of impact of this reclassification on ROM in BCs.

RESULTS

The incidence of NIFTP was 6.9% among excised thyroid nodules and 16.8% among all resected neoplastic lesions. ROM for BCs I to VI was 37.5%, 9.6%, 40.0%, 46.5%, 88.8%, and 96.8%, respectively. Risk of neoplasia was 50.0%, 13.8%, 55.0%, 71.2%, 88.8%, and 96.8% respectively. When NIFTPs were considered nonmalignant lesions, ROM decreased by 6.3%, 4.3%, 20%, 19.1%, 22.5%, and 1.5% in each Bethesda category (I-VI), respectively. Inability to diagnose NIFTP preoperatively led to overtreatment in 16.2%.

CONCLUSIONS

Prevalence of NIFTP in Asian countries may be higher than expected. Substantial cases of NIFTP have a benign preoperative cytology; hence, cases of follicular adenoma and adenomatous colloid nodule should be included in the review. NIFTP reclassification has significantly reduced the ROM in indeterminate BCs, suggesting diagnostic lobectomy rather than total thyroidectomy. Countries should establish their own malignancy risk range and parameters.

Pathological findings of the retrospective diagnosis of NIFTP (non-invasive follicular thyroid neoplasm with papillary-like nuclear features) in 84 cases from Turkey and systematic review

AIM

The terminology of "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was introduced in 2016; and estimated to cause significant effects in the clinical management of thyroid nodules. The aim of our study is to review our cases that were previously diagnosed as non-invasive encapsulated follicular variant PTC (NI/E-FVPTC) which are compatible with NIFTP and to correlate their follow-up.

METHOD

All thyroidectomy cases evaluated in the last 15 years were screened, and possible NIFTP cases were determined among patients with NI/E-FVPTC and they were re-examined microscopically. Revised histopathological criteria were used for the retrospective diagnosis of NIFTP. Histopathological findings were correlated to follow up information.

RESULTS

Totally 2138 cases had been previously diagnosed with PTC; 481 (22.5%) of them were FVPTC. After microscopic reevaluation of potential NIFTP cases, 84 cases (3.9%) received final diagnosis of NIFTP. 78.6% of NIFTP patients were female (F/M: 66/18); mean age was 49.0, tumor diameter was 22.7 mm and follow-up time was 66.4 months. 17.9% of NIFTP cases were multifocal and 13.1% were bilateral. No recurrence, lymph node involvement or distant metastasis was detected in any of the patients who were followed up. The mean age of the patients who had total thyroidectomy and received RAI was significantly higher than those who did not.

CONCLUSION

Although conservative treatment of NIFTP with lobectomy is recommended, age of the patients has been continuing to be the most important determinant for the clinicians to decide on total thyroidectomy and RAI ablation therapy at our institution.

Thyroid FNA terminology: The case for a single unified international system for thyroid FNA reporting

The use of reporting terminologies for thyroid FNA cytology enables standardisation and international alignment of the reporting of thyroid cytology results, which is essential. There are currently three major internationally recognised systems: Bethesda (TBS), UK RCPath (Thy), and Italian (TIR). A fourth terminology system used in Japan has identical categories to TBS but with different nomenclature. The aim of this review is to discuss the strengths and weaknesses of the TBS, UK RCPath, and TIR systems, and to make the case for international terminology harmonisation and standardisation.

Molecular Tests for Risk-Stratifying Cytologically Indeterminate Thyroid Nodules: An Overview of Commercially Available Testing Platforms in the United States

The past decade has witnessed significant advances in the application of molecular diagnostics for the pre-operative risk-stratification of cytologically indeterminate thyroid nodules. The tests that are currently marketed in the United States for this purpose combine aspects of tumor genotyping with gene and/or microRNA expression profiling. This review compares the general methodology and clinical validation studies for the three tests currently offered in the United States: ThyroSeq v3, Afirma GSC and Xpression Atlas, and ThyGeNEXT/ThyraMIR.

HBME1 and CK19 expression in non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) vs other follicular patterned thyroid lesions

BACKGROUND

Thyroid neoplasms with follicular architecture can have overlapping morphologic features and pose diagnostic confusion among pathologists. Various immunohistochemical stains have been investigated as potential diagnostic markers for PTC, among which HBME1 and CK19 have gained popularity. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) poses similar diagnostic challenges with interobserver variability and is often misdiagnosed as adenomatoid nodule or follicular adenoma. This study aims to evaluate expression of HBME1 and CK19 in NIFTPs in comparison to other well-differentiated thyroid neoplasms and benign mimickers.

METHOD

Seventy-three thyroid cases diagnosed over a period of 3 years at Methodist University Hospital, Memphis, TN, USA, were included in this study: 9 NIFTP; 18 papillary thyroid carcinoma (PTC); 11 follicular variant of papillary thyroid carcinoma, invasive (I-FVPTC); 24 follicular adenomas (FA); and 11 multinodular goiters/adenomatoid nodules (MNG). A tissue microarray (TMA) was constructed and HBME1 and CK19 immunohistochemistry was performed.

RESULTS

77.8% of NIFTPs, 88.9% of PTCs, 81.8% of I-FVPTCs, 16.7% of FAs, and 18.2% of MNGs showed HBME-1 expression. 66.7% of NIFTPs, 83.3% of PTCs, 81.8% of I-FVPTCs, 33.3% of FAs, and 45.4% of MNGs expressed CK19. Difference in expression of HBME1 and CK19 was statistically significant for NIFTP vs FA (qualitative; p < 0.05) and NIFTP vs MNG (p < 0.05). No statistically significant difference was found for HBME1 in NIFTP vs PTC (conventional and FVPTC), p ≥ 0.2. Sensitivity of HBME1 and CK19 for NIFTP were 78% and 67%, ~ 88% each for PTC, and 89% and 100% for FVPTC, respectively, while specificity of HBME1 and CK19 for NIFTP were 53% each, ~ 62% each for PTC, and ~55% each for FVPTC.

CONCLUSION

Our study indicated that HBME1 and CK19 are valuable markers in differentiating NIFTPs from morphologic mimics like follicular adenoma and adenomatoid nodules/multinodular goiter. While HBME1 and CK19 are both sensitive in diagnosing lesions with PTC-like nuclear features, CK19 stains a higher number of benign lesions in comparison to HBME1. No increase in sensitivity or specificity in diagnosis of NIFTP, PTC, or FVPTC was noted on combining the two antibodies.

Three ultrasound phenotypes of non-invasive follicular thyroid neoplasm with papillary-like nuclear features proposed for imaging-pathology analysis: single center experience

Background

The terminology "non-invasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was introduced to reduce overtreatment of thyroid carcinomas with indolent behavior. However, limited literature discussed the sonographic features of the entity in depth. The objective of this study is to summarize sonographic subtypes of NIFTP for precise diagnosis.

Methods

From January 2017 to June 2020, 13,531 consecutive patients underwent surgery for thyroid nodules were reviewed; 30 patients (0.22%) with 30 NIFTP were eligible for this retrospective observational study. We evaluated ultrasound features of all the lesions and distributed them into 3 major types of ultrasound appearance using pattern recognition. Systemic literature review concerning ultrasonography of NIFTP was also performed.

Results

At sonography, all the NIFTP lesions were classified into three types: 19 (63.3%) were categorized into type A-oval and solid nodule without other high-suspicion features, 7 (23.3%) into type B-partially cystic mass without high-suspicion features, 4 (13.3%) into type C-hypoechoic solid nodule with high-suspicion features including irregular margins, microcalcifications, taller-than-wide shape.

Conclusions

Three ultrasound patterns were proposed by us for ultrasound-cytopathology correlation analysis.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP): Diagnostic updates and molecular advances

The noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a strictly defined thyroid lesion, reclassified in 2016, in order to more accurately reflect the biological behavior of the tumor and thus, modify the way the lesion is clinically approached and perceived both by practitioners and patients. Additionally, this newly specified designation also allows for more uniformity in reporting for general pathologists less comfortable to exclude overt malignancy with certain nuclear features. In recent years, increasing molecular analyses correlated with longitudinal clinical outcomes have fostered improved diagnostic and treatment paradigms. Important revisions made to the definition of NIFTP in 2018 include the prohibition of any true papillae formation and the exclusion of lesions harboring the BRAF V600E mutation and other high-risk genetic abnormalities. These changes reflect the imperfection of the current criteria in outcome prediction and the global efforts for improvement. NIFTP are lesions with a wide range of size and cytomorphology. Although not addressed in the original series, large (≥4 cm) and oncocytic NIFTP have recently been shown to incur no recurrence or metastatic risk. Molecularly, NIFTP have a similar mutational profile as other follicular thyroid neoplasms, with frequent RAS family mutations and PAX8-PPARɤ fusions. However, the transcriptomic landscape is highly heterogenous, adding difficulty to gene expression-based cytopathologic classification. This review summarizes the evolution of the NIFTP concept and important advances in recent literature.

miRNA expression can classify pediatric thyroid lesions and increases the diagnostic yield of mutation testing

BACKGROUND

Genetic alterations in multiple cell signaling pathways are involved in the molecular pathogenesis of thyroid cancer. Oncogene mutation testing and gene-expression profiling are routinely used for the preoperative risk management of adult thyroid nodules. In this study, we evaluated the potential value of miRNA biomarkers for the classification of pediatric thyroid lesions.

PROCEDURE

Double-blind case-control study with 113 resected pediatric lesions: 66 malignant and 47 benign. Quantitative and qualitative molecular data generated with a 10-miRNA expression panel (ThyraMIR) and a next-generation sequencing oncogene panel (ThyGeNEXT) were compared with clinicopathological parameters.

RESULTS

miRNAs were differentially expressed in benign versus malignant tumors with distinct expression patterns in different histopathology categories. The 10-miRNA classifier identified 39 (59%) malignant lesions with 100% specificity. A positive classifier score was associated with lymph node metastasis, extrathyroidal extension and intrathyroidal spread. Genetic alterations associated with increased risk for malignancy were detected in 35 (53%) malignant cases, 20 positive for point mutations in BRAF, HRAS, KRAS, NRAS, PIK3CA, or TERT and 15 positive for gene rearrangements involving ALK, NTRK3, PPARG, or RET. The 10-miRNA classifier correctly identified 11 mutation-negative malignant cases. The performance of the combined molecular test was 70% sensitivity and 96% specificity with an area under the curve of 0.924.

CONCLUSIONS

These data suggest that the regulatory miRNA pathways underlying thyroid tumorigenesis are similar in adults and children. miRNA expression can identify malignant lesions with high specificity, augment the diagnostic yield of mutation testing, and improve the molecular classification of pediatric thyroid nodules.

The Bethesda System for Reporting Thyroid Cytology (TBSRTC): From look-backs to look-ahead

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was formalized in October 2007 by experts in thyroidology at the National Institute of Health in Bethesda, Maryland. The first edition of the TBSRTC book was published in 2010 and the second edition in 2018. The TBSRTC is widely employed in cytology practices in the United States and has also served as a model for similar tiered classification schemes for reporting thyroid cytopathology specimens. The tremendous success of TBSRTC cannot be underscored, it has provided a diagnostic framework which is well aligned with the present and the future of thyroid nodule management.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is rare, benign lesion using modified stringent diagnostic criteria: Reclassification and outcome study

BACKGROUND

Rigid diagnostic criteria for NIFTP have been recently proposed. The frequency of NIFTP using the new criteria is unknown, and whether abortive papillae are associated with BRAF^V600E mutation has not been studied. The aim of this study is to identify NIFTP by a retrospective review of Follicular Variant of Papillary Thyroid Carcinoma (FVPTC), and to study its incidence as well as the association between immunohistochemical BRAF^V600E expression and abortive papillae in NIFTP.

DESIGN

Thyroid tumors diagnosed as FVPTC or NIFTP over a period of 18 years (2000-2017) were identified using the laboratory information system. The final pathology reports were reviewed and potential NIFTP were retrieved. The archived slides for these cases were independently reviewed by 2 pathologists. BRAF^V600E (clone: VE1) immunostain was performed on representative tumor blocks. Clinical information including follow-up data was obtained from the electronic medical records.

RESULTS

Among the 1918 cases with the diagnosis of papillary thyroid carcinoma (PTC), 589 (30.7%) of FVPTC and 136 cases of potential NIFTP were identified. After the review of the archived pathology slides, 29 lesions were morphologically reclassified as NIFTP. Four (13.7%) of these were positive for BRAF^V600E; no association was found between the presence of abortive papillae and BRAF^V600Eexpression (p=0.3). Exclusion of the 4 cases with BRAF^V600Eexpression resulted in 25 lesions of final NIFTP, representing 4.2% of the FVPTC and 1.3% of the PTC. The mean age of the NIFTP patients was 50 years, 87.5% were females. The mean size of the lesions was 1.4 cm (0.1-4.0 cm). Intranuclear pseudoinclusions were not identified, and abortive papillae were identified in 60% of NIFTP. The average follow-up was 70 (28-166) months. There were no adverse events (recurrence or metastasis) in the NIFTP group.

CONCLUSION

When strictly defined, NIFTP comprises 1.3% of cases perviously classified as PTC. In morphological NIFTP, no correlation is found between the presence of abortive papillae and the BRAF^V600E expression. Intranuclear pseudo-inclusions are not observed in NIFTP. Modification of current morphological criteria to include BRAF^V600E immunohistochemistry test may stratify NIFTP with benign outcome.

Thyroid Bethesda Category AUS/FLUS in Our Microscopes: Three-Year-Experience and Cyto-Histological Correlation

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) introduced a new category: Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS) comprising of heterogenous lesions with a lesser degree of atypia. Its routine use is a bit controversial. The study cohort included AUS/FLUS thyroid cytopathological diagnoses signed out at Fimlab Laboratories from the period of 1 October 2013 to 31 December 2016. We analyzed all the AUS/FLUS cases, their cytology subclassification, and their cyto-histological correlation, when available. In total, there were 331 AUS/FLUS cases from 252 patients. The mean age was 59.8 years and there were 196 females and 56 males. Repeated AUS/FLUS was diagnosed in 75 (29.8%) cases. Out of 252 patients, 118 (46.8%) were operated on. Sixty-eight were operated on after the first AUS/FLUS diagnosis, 46 after 2 AUS/FLUS diagnoses, and 4 after 3 AUS/FLUS diagnoses. In total, there were 37 (14.7%) malignancies and 40 benign tumors. The risk of malignancy for AUS/FLUS (14.7%) is in agreement with the original TBSRTC risk of malignancy. The risk of neoplasia was 30.6% in our series.

Fifty years of thyroid pathology: concepts and developments

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

Controversies Regarding the Interpretation of Follicular Thyroid Nodules

Context.—

Follicular nodules are the most common source of diagnostic difficulties in the practice of surgical pathology of the thyroid. This is due to a variety of factors, the most salient of which is the lack of well-defined criteria and evidence-based data for the diagnosis of these lesions.

Objectives.—

To discuss some of the assumptions that have been accrued over the years regarding the criteria by which we evaluate such lesions.

Data Sources.—

The information presented herein is based on review of the literature and the author's personal experience.

Conclusions.—

Thyroid nodules with a predominant follicular growth pattern span the range from benign lesions (hyperplastic nodules, adenomatoid nodules, follicular adenomas) to malignant neoplasms (follicular carcinoma, follicular variant of papillary carcinoma) with a host of intermediate or indeterminate lesions found in between. Advances in immunohistochemistry and molecular pathology have not yet provided a reliable way of separating the borderline or intermediate cases. Low-grade and intermediate or borderline follicular-patterned thyroid lesions are those most often prone to difficulties for interpretation. Newer and potential future approaches for the evaluation of these lesions are discussed.

Clinical-pathological issues in thyroid pathology: study on the routine application of NIFTP diagnostic criteria

In 2017, the WHO classification of tumours of the endocrine organs established the criteria for a NIFTP diagnosis. The present paper considers some aspects that are still debated or unresolved: the real incidence and clinical meaning of multifocal/multinodular lesions, the biological behaviour of micro-NIFTP, the sprinkling phenomenon and the corresponding modifications to the FNA reporting systems based on changes to the ROM. Moreover, the paper suggests possible scenarios for the clinical-pathological management of this entity. From the initial 1470 cases, a group of 68 NIFTPs was recruited in a 9 year-long period. The average age at diagnosis was 55 years. The average diameter of the lesion was 1.7 cm (0.1 cm–10 cm). In 41 cases (60.1%), the lesion was inserted in the context of a multinodular background. In 12 cases, the diagnosis was incidental and the pre- operative FNA was performed on a different target. In 10 out of 68 cases, there was a multifocal NIFTP; in 14.7% of patients, PTC-like nuclear features showed sprinkling phenomenon. The cytological revision allocated 21 cases (49%) to the SIAPEC TIR3 indeterminate class and a nuclear score 2 or 3 were identified in 25 smears. Multifocality is part of the spectrum of NIFTPs, that can arise in a multinodular background with variable sizes from microscopic lesions to very large ones. Cytopathological criteria such as an evaluation of the nuclear score may help the pathologists in promoting a NIFTP diagnosis in the preoperative setting.