Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP): a review for clinicians

Validating the Modified McGill Thyroid Nodule Score for Assessment of Preoperative Risk of Pediatric Thyroid Malignancy

OBJECTIVE

The McGill Thyroid Nodule Score (MTNS) is a preoperative tool used to predict the risk for well-differentiated thyroid cancer in adults. It was developed by a multidisciplinary team using established evidence-based risk factors for thyroid cancer. The modified McGill Thyroid Nodule Score (mMTNS) was developed to predict malignancy risk in children. A pilot study suggested the mMTNS was able to assess malignancy risk in children with indeterminate cytology on fine needle aspiration (FNA). This study seeks to validate these findings.

METHODS

Retrospective chart review identified subjects who underwent FNA biopsy and subsequent resection. Each patient was assigned a score to compare to final pathology. Statistical analysis was performed with SPSS. All tests were 2-tailed and statistical significance defined p < 0.05. Logistic regression used to determine predictive values of scores.

RESULTS

46 patients ≤21 years of age underwent resection of a thyroid nodule. Female predominance of 85% (n = 39). 78% (n = 36) of patients had palpable nodule. 65% (n = 30) found to have benign pathology and 35% (n = 16) found to have malignancy. Malignant nodules associated with greater mean mMTNS compared to benign [13.63 vs 7.23]. An mMTNS greater >12 had sensitivity of 86.7%, specificity of 90.3%, positive predictive value of 81.3%, and negative predictive value of 93.3%.

CONCLUSION

Our data suggests the mMTNS continues to be a useful adjunct in predicting malignancy risk of pediatric thyroid nodules. An mMTNS >12 has a high risk for malignancy, which can aid in counseling and clinical decision making, particularly when there is indeterminate cytology on FNA.

LEVEL OF EVIDENCE

IV.

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.

Emerging therapeutic options for follicular-derived thyroid cancer in the era of immunotherapy

Although most follicular-derived thyroid cancers are well differentiated and have an overall excellent prognosis following treatment with surgery and radioiodine, management of advanced thyroid cancers, including iodine refractory disease and poorly differentiated/undifferentiated subtypes, is more challenging. Over the past decade, better understanding of the genetic drivers and immune milieu of advanced thyroid cancers has led to significant progress in the management of these patients. Numerous targeted kinase inhibitors are now approved by the U.S Food and Drug administration (FDA) for the treatment of advanced, radioiodine refractory differentiated thyroid cancers (DTC) as well as anaplastic thyroid cancer (ATC). Immunotherapy has also been thoroughly studied and has shown promise in selected cases. In this review, we summarize the progress in the understanding of the genetic landscape and the cellular and molecular basis of radioiodine refractory-DTC and ATC, as well as discuss the current treatment options and future therapeutic avenues.

Follow-up and Outcomes of 186 Patients With Follicular Cell-Derived Thyroid Cancer Seen at a Referral Center by One Thyroidologist in 2015

OBJECTIVE

To study the profile, management, and outcomes of follicular cell-derived thyroid cancer (FCDTC) before publication of the 2016 American Thyroid Association guidelines recommending less-aggressive thyroid cancer procedures.

METHODS

Patients with FCDTC were seen by one thyroidologist at Mayo Clinic during the 2015 calendar year. Patients underwent surgical procedures for FCDTC in 2015 or earlier at Mayo Clinic or another institution. Follow-up data were collected from January 1, 2016, through July 20, 2022. Outcomes measured included tumor characteristics, treatment methods, adverse effects, diagnostic imaging methods, and primary tumor/metastasis status at the last follow-up.

RESULTS

Of 186 included patients, 85 had total or near-total thyroidectomy. Bilateral disease was present in 35.5% of these patients, and contralateral involvement would have been missed by lobectomy for 9 (10%) patients with low-risk thyroid cancer. Additionally, 57% had positive neck lymph nodes identified during their surgical procedure, 25% (21% in central compartment) of which were undetected by preoperative ultrasonography. At the last follow-up, 65.6% of patients had no evidence of disease and 10.7% had distant metastases.

CONCLUSION

This report outlines the profile and outcomes of patients with FCDTC who were treated at a referral center before the revised 2016 American Thyroid Association guidelines. Lobectomy for low-risk FCDTC may miss some cancer in the contralateral lobe. However, the clinical importance of these missed microcarcinomas is unclear. Preoperative ultrasonography effectively predicts lateral, but not central compartment, nodal metastases.

Digital analyses of nuclear features can help discriminate among non-invasive follicular thyroid neoplasm with papillary-like nuclear features, papillary thyroid carcinoma follicular subtype, and follicular carcinoma in cytological specimens

BACKGROUND

As it stands, the diagnosis of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is primarily based on histological analysis. We hypothesised that computerised analysis of nuclear images of cytological specimens could be used to differentiate NIFTP from papillary thyroid carcinoma follicular subtype (PTCFS) and follicular carcinoma (FC), influencing patient management.

METHODS

We employed a retrospective analytical observational study based on nuclear morphometric variables of cytological material from thyroid nodules classified as PTCFS, NIFTP, or FC. Five cases of each entity were analysed. Cytological slides were photographed, and 1170 cells for each entity were analysed digitally. The captured images were evaluated (blindly) using the ImageJ software package. The morphometric evaluation included area, perimeter, width, height, and circularity. Numerical variables were expressed as mean, median, minimum, and maximum (min; max) values. Kruskal-Wallis and Dunn's tests were used with a 5% significance level.

RESULTS

Regarding nuclear analysis, all variables differed among the three groups (p < 0.001). Given the interdependence among the variables, these data indicated that nuclear size was greatest in the NIFTP group, followed by FC and PTCFS.

DISCUSSION/CONCLUSION

Our analysis of the digital images, with a focus on nuclear parameters, found significantly difference among cytological specimens from cases of NIFTP, PTCFS and FC. Thus, this tool has the potential to provide additional information that may help in the diagnosis of NIFTP, even during the preoperative period. Additional studies are needed to create protocols, evaluate the applicability of nuclear morphological and morphometric parameters-focusing on digital pathology-and create algorithms and tools to assist cytopathologists with their diagnostic routines.

Three-dimensional nuclear architecture distinguishes thyroid cancer histotypes

Molecular markers can serve as diagnostic tools to support pathological analysis in thyroid neoplasms. However, because the same markers can be observed in some benign thyroid lesions, additional approaches are necessary to differentiate thyroid tumor subtypes, prevent overtreatment and tailor specific clinical management. This applies particularly to the recently described variant of thyroid cancer referred to as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). This variant has an estimated prevalence of 4.4% to 9.1% of all papillary thyroid carcinomas worldwide. We studied 60 thyroid lesions: 20 classical papillary thyroid carcinoma (CPTC), 20 follicular variant of PTC (FVPTC) and 20 NIFTP. We examined morphological and molecular features to identify parameters that can differentiate NIFTP from the other PTC subtypes. When blindly investigating the nuclear architecture of thyroid neoplasms, we observed that NIFTP has significantly longer telomeres than CPTC and FVPTC. Super-resolved 3D-structured illumination microscopy demonstrated that NIFTP is heterogeneous and that its nuclei contain more densely packed DNA and smaller interchromatin spaces than CPTC and FVPTC, a pattern that resembles normal thyroid tissue. These data are consistent with the observed indolent biological behavior and favorable prognosis associated with NIFTP, which lacks BRAFV600E mutations. Of note, next-generation thyroid oncopanel sequencing was unable to distinguish the thyroid cancer histotypes in our study cohort. In summary, our data suggest that 3D nuclear architecture can be a powerful analytical tool to diagnose and guide clinical management of NIFTP.

Clinical use of Molecular Data in Thyroid Nodules and Cancer

Over the past 3 decades, advances in the molecular genetics of thyroid cancer (TC) have been translated into diagnostic tests, prognostic markers, and therapeutic agents. The main drivers in differentiated TC pathogenesis are single-point mutations and gene fusions in components of the Mitogen-activated protein kinase (MAPK) and phosphoinositide-3-kinase-protein kinase B/Akt (PI3K/Akt) pathways. Other important genetic alterations in the more advanced types of TC include TERT promoter, TP53, EIF1AX, and epigenetic alterations. Using this knowledge, several molecular tests have been developed for cytologically indeterminate thyroid nodules. Currently, 3 commercially available tests are in use including a DNA/RNA-based test (ThyroSeq v.3), an RNA-based test (Afirma Gene Sequencing Classifier), and a hybrid DNA/miRNA test, ThyGeNEXT/ThyraMIR. These tests are mostly used to rule out malignancy in Bethesda III and IV thyroid nodules because they all have high sensitivities and negative predictive values. Their common use, predominantly in the United States, has resulted in a significant reduction in unnecessary thyroid surgeries for benign nodules. Some of these tests also provide information on the underlying molecular drivers of TC; this may support decision making in initial TC management planning, although this practice has not yet been widely adopted. More importantly, molecular testing is essential in patients with advanced disease before using specific mono-kinase inhibitors (eg, selpercatinib for RET-altered TC) because these drugs are ineffective in the absence of a specific molecular target. This mini-review discusses the utilization of molecular data in the clinical management of patients with thyroid nodules and TC in these different clinical situations.

Additional Oncogenic Alterations in RAS-Driven Differentiated Thyroid Cancers Associate with Worse Clinicopathologic Outcomes

PURPOSE

RAS mutations occur across the spectrum of thyroid neoplasms, and more tools are needed for better prognostication. The objective of this study was to evaluate how additional genetic events affecting key genes modify prognosis in patients with RAS-mutant thyroid cancers, and specifically differentiated thyroid cancers (DTC).

EXPERIMENTAL DESIGN

We performed a clinical-genomic analysis of consecutive patients with DTC, poorly differentiated (PDTC), or anaplastic thyroid cancer (ATC) between January 2014 and December 2021, in whom a custom-targeted next-generation sequencing assay was performed. Patients harboring RAS mutations were included, and we compared their clinical features and outcomes based upon the presence of additional oncogenic alterations.

RESULTS

Seventy-eight patients were identified, with 22% (17/78) harboring a driver RAS mutation plus an additional oncogenic alteration. All six (100%) ATCs had an additional mutation. Compared with DTCs harboring a solitary RAS mutation, patients with DTC with RAS and additional mutation(s) were more likely to be classified as American Thyroid Association high-risk of recurrence (77% vs. 12%; P < 0.001) and to have larger primary tumors (4.7 vs. 2.5 cm; P = 0.002) and advanced stage (III or IV) at presentation (67% vs. 3%; P < 0.001). Importantly, over an average 65-month follow-up, DTC-specific-mortality was more than 10-fold higher (20% vs. 1.8%; P = 0.011) when additional mutations were identified.

CONCLUSIONS

Identification of key additional mutations in patients with RAS-mutant thyroid cancers confers a more aggressive phenotype, increases mortality risk in DTC, and can explain the diversity of RAS-mutated thyroid neoplasia. These data support genomic profiling of DTCs to inform prognosis and clinical decision-making.

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.

Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features: What a Surgeon Should Know

The inclusion of the less aggressive follicular form of papillary thyroid cancer (PTC) is associated with an increase in the incidence of the condition, with the follicular variant of PTC being the most common of all variants. The majority of individuals with the encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) are treated as though they have classic thyroid cancer, despite the availability of mounting evidence to contradict the aforementioned. According to numerous research, a certain type of noninvasive-EFVPTC (NI-EFVPTC) demonstrated poor histopathologic diagnostic reproducibility and has received aggressive treatment similar to that of a classical thyroid neoplasm. Therefore, to replace the term NI-EFVPC, a new nomenclature for these tumors, called "noninvasive follicular thyroid neoplasm with papillary-like nuclear characteristics" (NIFTP), was introduced in the year 2016. The present paper explores this recently introduced terminology, clinical, histologic, and molecular features, and diagnostic criteria.

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.

Clinicopathologic Characteristics of Pediatric Follicular Variant of Papillary Thyroid Carcinoma Subtypes: A Retrospective Cohort Study

Introduction: Follicular patterned thyroid nodules with nuclear features of papillary thyroid carcinoma (PTC) encompass a range of diagnostic categories with varying risks of metastatic behavior. Subtypes include the invasive encapsulated follicular variant of PTC (Ienc-fvPTC) and infiltrative fvPTC (inf-fvPTC), with tumors lacking invasive features classified as noninvasive follicular thyroid neoplasms with papillary-like features (NIFTPs). This study aimed to report the clinical and histological features of pediatric cases meeting criteria for these histological subtypes, with specific focus on Ienc-fvPTC and inf-fvPTC. Methods: In this retrospective cohort study, pediatric patients with thyroid neoplasms showing follicular patterned growth and nuclear features of PTC noted on surgical pathology between January 2010 and January 2021 were retrospectively reviewed and classified according to the recent 2022 World Health Organization (WHO) criteria. Clinical and histopathologic parameters were described for NIFTP, Ienc-fvPTC, and inf-fvPTC subtypes, with specific comparison of Ienc-fvPTC and inf-fvPTC cases. Results: The case cohort included 42 pediatric patients, with 6 (14%), 25 (60%), and 11 (26%) patients meeting criteria for NIFTP, Ienc-fvPTC, and inf-fvPTC, respectively. All cases were rereviewed, and 5 patients originally diagnosed with Ienc-fvPTC before 2017 were reappraised as having NIFTPs. The NIFTP cases were encapsulated tumors without invasive features, lymph node or distant metastasis, or disease recurrence. Ienc-fvPTC tumors demonstrated clearly demarcated tumor capsules and capsular/vascular invasion, while inf-fvPTC tumors displayed infiltrative growth lacking a capsule. inf-fvPTC cases had increased prevalence of malignant preoperative cytology, lymph node metastasis, and distant metastasis (p < 0.01). These cases were treated with total thyroidectomy, lymph node dissection, and subsequent radioactive iodine therapy. Preliminary genetic findings suggest a predominance of fusions in inf-fvPTC cases versus point mutations in Ienc-fvPTC (p = 0.02). Conclusions: Pediatric NIFTP and fvPTC subtypes appear to demonstrate alignment between clinical and histological risk stratification, with indolent behavior in Ienc-fvPTC and invasive features in inf-fvPTC tumors.

Reclassification as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP): A retrospective review in a single institution and outcome study

Background/Aim: Since non-invasive follicular thyroid neoplasm (NIFTP) was first defined in 2016, past overtreatment status, impact for the risk of malignancy, and incidence of NIFTP have been the subject of study. Retrospective cohort studies have been published and present widely varying results in different geographic regions. This study aimed to reclassify follicular variants of papillary thyroid carcinoma (FVPTC) cases diagnosed in a single center using the defined stringent NIFTP criteria and to determine incidence, clinicopathological features, and survival of NIFTP cases. Methods: This retrospective cohort study was conducted in a single center and consisted of patients with diagnosed follicular variant papillary thyroid carcinoma in thyroidectomy/thyroid lobectomy specimens between 2014 and 2021. Reports of FVPTC cases between 2014 and 2018 were evaluated by two experienced pathologists to identify candidates for NIFTP. Archived glass slides of the potential NIFTP cases were retrieved and reviewed independently by two pathologists.  Results: Between 2014 and 2021, 84 patients who underwent surgery were diagnosed with FVPTC. Reports of 49 patients diagnosed before 2018 were re-evaluated by two pathologists, and 20 cases were identified as candidates for NIFTP. After blind evaluation of pathology slides, five cases (10%) were diagnosed as NIFTP according to the criteria established before 2016, and two cases between 2016 and August 2018 were still diagnosed as NIFTP. Fourteen patients were diagnosed with NIFTP between 2014 and 2021. The median follow-up of the NIFTP patients was 4.3 years, and no recurrence and/or metastasis was reported. Conclusion: NIFTP represents 7.6% of the papillary thyroid carcinoma (PTC) cases in our cohort, which is higher than the incidence rate in our country. The follow-up results of our cases were uneventful considering the indolent nature of NIFTP, but we had high thyroidectomy rates. Due to the concomitant PTC, multifocality, and uncertainties in the follow-up routine, we think it would be appropriate for these patients to remain in active follow-up.

Non-invasive follicular neoplasm with papillary-like nuclear features: a challenging and infrequent entity in Argentina

PURPOSE

Non-invasive encapsulated follicular variant of papillary thyroid cancer was reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). These neoplasms have an extremely low malignant potential. The aim of this study was (1) to assess the prevalence of NIFTP in patients with papillary thyroid carcinoma, (2) to evaluate their outcomes, and (3) to determine their molecular profile.

METHODS

Multicenter, descriptive, retrospective study. Patients with papillary thyroid cancer diagnosed from January 2006 to December 2016 from 11 referral centers were included. Diagnosis of NIFTP was based on criteria described by Nikiforov et al. in 2018. At least two pathologists agreed on the diagnosis. Two thousand six hundred and seventy-seven papillary thyroid cancer patients were included; 456 (17%) of them were follicular variant papillary thyroid cancer, and 30 (1.12%) fulfilled diagnostic criteria for NIFTP.

RESULTS

Each of the 30 included patients underwent a total thyroidectomy, and 50% were treated with radioiodine (median dose 100 mCi). After a median follow-up of 37 months, 84% of patients had an excellent response, 3% had an indeterminate response and data was missing in the remaining 13%. No metastatic lymph nodes, distant metastases or recurrences were found. RAS mutations were detected in 4 patients (13%).

CONCLUSION

The prevalence of NIFTP in our series is amongst the lowest reported. Excellent outcomes of patients underscore their low malignant potential. Molecular findings differ from other series, probably related to environmental or ethnic features of our population and the meticulous criteria for diagnosing NIFTP.

Deep Learning-Based Recognition of Different Thyroid Cancer Categories Using Whole Frozen-Slide Images

Introduction: The pathological rare category of thyroid is a type of lesion with a low incidence rate and is easily misdiagnosed in clinical practice, which directly affects a patient’s treatment decision. However, it has not been adequately investigated to recognize the rare, benign, and malignant categories of thyroid using the deep learning method and recommend the rare to pathologists.

Methods: We present an empirical decision tree based on the binary classification results of the patch-based UNet model to predict rare categories and recommend annotated lesion areas to be rereviewed by pathologists.

Results: Applying this framework to 1,374 whole-slide images (WSIs) of frozen sections from thyroid lesions, we obtained an area under a curve of 0.946 and 0.986 for the test datasets with and without WSIs, respectively, of rare types. However, the recognition error rate for the rare categories was significantly higher than that for the benign and malignant categories (p < 0.00001). For rare WSIs, the addition of the empirical decision tree obtained a recall rate and precision of 0.882 and 0.498, respectively; the rare types (only 33.4% of all WSIs) were further recommended to be rereviewed by pathologists. Additionally, we demonstrated that the performance of our framework was comparable to that of pathologists in clinical practice for the predicted benign and malignant sections.

Conclusion: Our study provides a baseline for the recommendation of the uncertain predicted rare category to pathologists, offering potential feasibility for the improvement of pathologists’ work efficiency.

Synchronous follicular carcinoma and non-invasive follicular thyroid neoplasm with papillary like nuclear features in thyroid-A case report

Follicular carcinoma of the thyroid accounts for 5-15% of all the primary cancers of thyroid. Follicular carcinoma clinically manifests as a painless neck mass and rarely presents with  metastatic bony lesion, the most common site being the spine. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) constitute  10-20% of all thyroid cancers. The histopathological diagnosis of thyroid follicular carcinoma mandates demonstration of either capsular/vascular invasion. Differentiating between follicular carcinoma and NIFTP is challenging based on histology. Hence extensive sampling of the pathological specimen is required to differentiate the same. Herein we report a case of an elderly woman presented with a pathological fracture of the femur due to metastasis from follicular carcinoma of the thyroid with an incidental NIFTP of the left lobe of the thyroid.  

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.

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

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

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

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

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

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

Radiofrequency ablation and thyroid cancer: review of the current literature

BACKGROUND

Thyroid nodules are commonly being diagnosed in general population and have a potential for malignant transformation. Historically, surgery has been considered as the first line treatment for these tumors. However, with passage of time newer minimally invasive techniques such as RFA (radiofrequency ablation) has been adapted. Though, RFA for thyroid tumors has been performed more commonly in Asian and European countries, it is a fairly new technique in North America. The aim of the review is to assess the current data and conclude that whether RFA is likely a valuable option when compared to surgery for treatment of thyroid tumors.

MATERIALS AND METHODS

A Comprehensive PubMed/MEDLINE, Embase and Web of Science search was performed. To expand our search, references of the retrieved articles were also screened for additional data. After selecting the studies that fulfilled the initial screening, authors independently reviewed the selected studies and screened the full texts to identify those that met the inclusion criteria.

RESULTS

The comprehensive literature search from PubMed/MEDLINE, Web of Science, and EMBASE databases revealed 1094 studies (Embase 870, PubMed 200, and Web of Science 24). References were imported for screening. Amongst 1094 studies, 138 duplicates removed, and 956 studies were screened against title and abstract. After these 777 studies were excluded the remaining 179 studies were assessed for full-text eligibility. Amongst them 127 studies excluded due to wrong design or setting. Finally, 18 studies were included in the review.

CONCLUSION

RFA appears to be a safe alternative to surgery in selected cases. However, it is not widely used and there are few randomized controlled trials. Furthermore, it is associated with a low risk profile and has shown promising results in patients who are difficult surgery candidates. Currently large-scale prospective studies are needed in North America to establish the efficacy of RFA and its use as an alternative to surgery for thyroid tumors.

Non-invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) lowers the risk of malignancy in the bethesda system for reporting thyroid cytopathology diagnostic categories

Background:

The introduction of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has been shown to decrease the risk of malignancy (ROM) in The Bethesda System for Reporting Thyroid Cytopathology. This knowledge may alter the management of patients with thyroid nodules.

Objectives:

To correlate cytological diagnosis with histological diagnosis for establishing the ROM of all Bethesda system categories after the introduction of NIFTP.

Methods:

This was a retrospective cohort study. All consecutive fine-needle aspiration cytology (FNAC) specimens collected from January 1, 2013, to December 31, 2017, at King Abdullah Medical City, Jeddah, Saudi Arabia, were assessed, and patients who underwent surgical excision of thyroid nodules were further analyzed. The ROM and overall ROM for each Bethesda category were calculated with and without considering NIFTP as a malignant tumor.

Results:

Overall, 1066 FNAC specimens were collected, of which 281 had a surgical correlation. Our cases included 18 (6.4%) non-diagnostic (ND), 109 (38.8%) benign, 28 (9.9%) atypia/follicular lesion of undetermined significance (AUS/FLUS), 39 (13.8%) follicular neoplasm or suspicion for follicular neoplasm (FN/SFN), 20 (7.1%) suspicion for malignancy (SM), and 67 (23.8%) malignant (POM) cases. After considering NIFTP diagnosis on resection specimens, the ROM decreased as follows: ND, 38.8% to 27.7% (P = 0.2388); benign, 21.1% to 11.9% (P = 0.0343); AUS/FLUS, 50% to 39.2% (P = 0.2089); FN/SFN, 53.8% to 33.3% (P = 0.0336); SM, 85% to 75% (P = 0.2147); POM, 95.5% to 88% (P = 0.0582).

Conclusion:

The introduction of NIFTP would significantly decrease the ROM of thyroid FNAC in both benign and FN/SFN categories of the Bethesda system.

Trends in Diagnosis of Noninvasive Follicular Thyroid Neoplasm With Papillarylike Nuclear Features and Total Thyroidectomies for Patients With Papillary Thyroid Neoplasms

Importance

Increasing detection of early-stage papillary thyroid neoplasms without improvements in mortality has prompted development of strategies to prevent or mitigate overtreatment.

Objective

To determine adoption rates of 2 recent strategies developed to limit overtreatment of low-risk thyroid cancers: (1) a new classification, noninvasive follicular thyroid neoplasm with papillarylike nuclear features (NIFTP), and (2) hemithyroidectomy for selected papillary thyroid carcinomas (PTCs) up to 4 cm in size.

Design, Setting, and Participants

This is a cross-sectional analysis of 3368 pathology records of 2 cohorts of patients from 18 hospitals in 6 countries during 2 time periods (2015 and 2019). Participating hospitals were included from the US (n = 12), Canada (n = 2), Denmark (n = 1), South Korea (n = 1), South Africa (n = 1), and India (n = 1). The records of the first 100 patients per institution for each year who underwent thyroid-directed surgery (hemithyroidectomy, total thyroidectomy, or completion thyroidectomy) were reviewed.

Main Outcomes and Measures

Frequency of diagnosis of NIFTP, PTCs, and thyroidectomies during the study period.

Results

Of the 790 papillary thyroid neoplasms captured in the 2019 cohort, 38 (4.8%) were diagnosed as NIFTP. Diagnosis of NIFTP was observed in the US, South Africa, and India. There was minimal difference in the total proportion of PTCs in the 2015 cohort compared with the 2019 cohort (778 [47.1%] vs 752 [44.5%]; difference, 2.6% [95% CI, -16.9% to 22.1%]). The proportion of PTCs eligible for hemithyroidectomy but treated with total thyroidectomy in the 2 cohorts demonstrated a decreasing trend from 2015 to 2019 (341 of 453 [75.3%] vs 253 of 434 [58.3%]; difference, 17.0% [95% CI, -1.2% to 35.2%]).

Conclusions and Relevance

Results of this cohort study showed that the 2 mitigation strategies for preventing overtreatment of early-stage thyroid cancer have had mixed success. The diagnosis of NIFTP has only been applied to a small proportion of thyroid neoplasms compared with expected rates. However, more patients eligible for hemithyroidectomy received it in 2019 compared with 2015, showing some success with this deescalation strategy.

Immunohistochemistry Helps to Distinguish Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features/Noninvasive Encapsulated Follicular Variant of Papillary Thyroid Carcinoma with Other Follicular Thyroid Lesions

Background and Objectives: We aimed to assess the diagnostic value of various immunohistochemical (IHC) markers and panels for differentiation among benign follicular nodules (BFNs), noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTPs), noninvasive encapsulated follicular variants of papillary thyroid carcinoma (NEFVPTCs), and infiltrative FVPTC (IFVPTC). Materials and Methods: Sixty-three cases were classified as BFNs, NIFTPs, NEFVPTCs, or IFVPTCs and were evaluated using the following markers: CK19, CD56, galectin-3, CITED1, HBME-1, VE1, and TROP-2. Results: The IHC results for NIFTP and NEFVPTC exhibited no statistically significant differences. In differentiating IFVPTCs from BFNs and NIFTPs/NEFVPTCs, galectin-3 and TROP-2 were the markers with the highest sensitivity plus high specificity, respectively. In various combinations, panel co-expression of two markers, including galectin-3 and/or HBME-1 and/or TROP-2, and the combination of galectin-3 and TROP-2 co-expression could achieve 100% in all aspects. In terms of discrimination of BFNs from NIFTP/NEFVPTC, CK19 was the single most sensitive marker (81.3%), while CD56 was the most specific (100%). The panel consisting of CK19 and/or HBME-1 exhibited the greatest sensitivity (96.9%), but the panel with CD56 and/or HBME-1 exhibited the greatest specificity (90.5%). Conclusions: Our results broaden the use of IHC markers for differential diagnoses among the four groups of follicular-based lesions. In addition, the similar IHC profiles of NIFTP and NEFVPTC also suggest the original criterion of <1% papillae within tumors, providing a reliable NIFTP diagnosis. Their close relationship may represent a spectrum of progressing neoplasia.

Bone metastasis from noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP); a case report

BACKGROUND

The term non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was recently proposed as a non-malignant thyroid lesion with indolent behavior that does not require post-operative radio-iodine treatment. We are reporting a case of NIFTP with bone metastasis that is the second case reported so far.

CASE PRESENTATION

We describe a 38-year-old woman who presented with an indeterminate thyroid nodule and underwent total thyroidectomy with the finding of NIFTP on careful pathologic examination. However, her initial follow-up evaluation revealed a serum thyroglobulin level of > 300 ng/ml and a diagnostic whole body ¹³¹I scan demonstrated a focus of increased uptake in the left hemipelvis, confirmed on CT scan to be a lytic lesion in the left iliac bone. She was treated with 7.4GBq (200 mCi) of ¹³¹I and her follow-up 1 year later revealed an undetectable serum thyroglobulin and a negative whole body ¹³¹I scan with no visible uptake in the iliac bone indicating an excellent response.

CONCLUSION

This case presentation reminds us to be alert to the rare occurrence of distant metastasis in NIFTP and the need for a case by case analysis and continuing post-operative follow-up for detection of residual or recurrent disease.

An integrated AI model to improve diagnostic accuracy of ultrasound and output known risk features in suspicious thyroid nodules

OBJECTIVES

From the viewpoint of ultrasound (US) physicians, an ideal thyroid US computer-assisted diagnostic (CAD) system for thyroid cancer should perform well in suspicious thyroid nodules with atypical risk features and be able to output explainable results. This study aims to develop an explainable US CAD model for suspicious thyroid nodules.

METHODS

A total of 2992 solid or almost-solid thyroid nodules were analyzed retrospectively. All nodules had pathological results (1070 malignancies and 1992 benignities) confirmed by ultrasound-guided fine-needle aspiration cytology and histopathology after thyroidectomy. A deep learning model (ResNet50) and a multiple risk features learning ensemble model (XGBoost) were used to train the US images of 2794 thyroid nodules. Then, an integrated AI model was generated by combining both models. The diagnostic accuracies of the three AI models (ResNet50, XGBoost, and the integrated model) were predicted in a testing set including 198 thyroid nodules and compared to the diagnostic efficacy of five ultrasonographers.

RESULTS

The accuracy of the integrated model was 76.77%, while the mean accuracy of the ultrasonographers was 68.38%. Of the risk features, microcalcifications showed the highest contribution to the diagnosis of malignant nodules.

CONCLUSIONS

The integrated AI model in our study can improve the diagnostic accuracy of suspicious thyroid nodules and output the known risk features simultaneously, thus aiding in training young ultrasonographers by linking the explainable results to their clinical experience and advancing the acceptance of AI diagnosis for thyroid cancer in clinical practice.

KEY POINTS

• We developed an artificial intelligence (AI) diagnosis model based on both deep learning and multiple risk feature ensemble learning methods. • The AI diagnosis model showed higher diagnostic accuracy for suspicious thyroid nodules than ultrasonographers. • The AI diagnosis model showed partial explainability by outputting the known risk features, thus aiding young ultrasonic doctors in increasing the diagnostic level for thyroid cancer.

Rate of non-invasive follicular thyroid neoplasms with papillary-like nuclear features depends on pathologist's criteria: a multicentre retrospective Southern European study with prolonged follow-up

PURPOSE

To determine the rate of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in a multi-institutional series from the Iberian Peninsula and describing this NIFTP cohort.

METHODS

Retrospective study of papillary thyroid carcinoma (PTC) or well-differentiated tumours of uncertain malignant potential (WDT-UMP) diagnosed between 2005 and 2015 and measuring ≥5 mm in adult patients from 17 hospitals. Pathological reports were reviewed to determine the cases that fulfil the original criteria of NIFTP and histology was reassessed. Rates were correlated with the number of PTC and its follicular variant (FVPTC) of each institution. Demographic data, histology, management, and follow-up of the reclassified NIFTP cohort were recorded.

RESULTS

A total of 182 cases with NIFTP criteria were identified: 174/3372 PTC (rate: 5.2%; range: 0-12.1%) and 8/19 WDT-UMP (42.1%). NIFTP rate showed linear correlation with total PTC (p: 0.03) and FVPTC (p: 0.007) identified at each centre. Ultrasound findings were non-suspicious in 60.1%. Fine-needle cytology or core biopsy diagnoses were undetermined in 49.7%. Most patients were treated with total thyroidectomy. No case had nodal disease. Among patients with total thyroidectomy, 89.7% had an excellent response evaluated 1 year after surgery. There were no structural persistence or relapses. Five patients showed residual thyroglobulin after 90 months of mean follow-up.

CONCLUSIONS

NIFTP rate is low but highly variable in neighbouring institutions of the Iberian Peninsula. This study suggests pathologist's interpretation of nuclear alterations as the main cause of these differences. Patients disclosed an excellent outcome, even without using the strictest criteria.

Thyroid cancer, recent advances in diagnosis and therapy

Over the past several decades, the approach to the diagnosis and management of patients with follicular cell-derived thyroid cancer has evolved based on improved classification of patients better matching clinical outcomes, as well as advances in imaging, laboratory, molecular technologies and knowledge. While thyroid surgery, radioactive iodine therapy and TSH suppression remain the mainstays of treatment, this expansion of knowledge has enabled de-escalation of therapy for individuals diagnosed with low-risk well-differentiated thyroid cancer; better definition of treatment choices for patients with more aggressive disease; and improved ability to optimize treatments for patients with persistent and/or progressive disease. Most recently, the advancement of knowledge regarding the molecular aspects of thyroid cancer has improved thyroid cancer diagnosis and has enabled individualized therapeutic options for selected patients with the most aggressive forms of the disease. Guidelines from multiple societies across the world reflect these changes, which focus on taking a more individualized approach to clinical management. In this review, we discuss the current more personalized approach to patients with follicular cell-derived thyroid cancer and point toward areas of future research still needed in the field.

Challenges in Cytology Specimens With Hürthle Cells

In fine-needle aspirations (FNA) of thyroid, Hürthle cells can be found in a broad spectrum of lesions, ranging from non-neoplastic conditions to aggressive malignant tumors. Recognize them morphologically, frequently represents a challenging for an adequately diagnosis and are associated with a significant interobserver variability. Although the limitations of the morphologic diagnosis still exist, the interpretation of the context where the cells appear and the recent advances in the molecular knowledge of Hürthle cells tumors are contributing for a more precise diagnosis. This review aims to describe the cytology aspects of all Hürthle cells neoplastic and non-neoplastic thyroid lesions, focusing on the differential diagnosis and reporting according to The Bethesda System for Reporting Thyroid Cytology (TBSRTC). New entities according to the latest World Health Organization (WHO) classification are included, as well as an update of the current molecular data.

First bilateral non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) co-occurring with bilateral papillary thyroid microcarcinoma. Case report and literature review

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Non-invasive follicular thyroid neoplasm with papillary-like features (NIFTP) is a benign lesion with no evidence of recurrence or metastasis.

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NIFTP is managed with partial or total thyroidectomy which is sufficient to achieve total cure.

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Co- coexistence of NIFTP and papillary microcarcinoma can be managed by resection and radioactive iodine ablation of the thyroid.

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The current case in probably the first reported bilateral NIFTP with bilateral papillary microcarcinoma.

Introduction

Non-invasive follicular thyroid neoplasm with papillary-like features (NIFTP) is a recently characterized lesion with very low malignant potential. This has allowed for less aggressive management of this tumor subtype. Papillary thyroid carcinoma (PTC) has malignant potential and requires different considerations in management.

Presentation of case

A 33-year-old woman presented to our Thyroid Surgery Clinic with a left neck swelling slowly enlarging over 4 years, and recent right-sided neck pain. Neck ultrasound and fine needle aspiration for cytology found bilateral thyroid nodules, labelled as ‘follicular lesion of undetermined significance’ (FLUS). Final pathology report after total thyroidectomy identified four distinct tumors: bilateral NIFTP lesions and bilateral papillary microcarcinomas.

Discussion

Management of NIFTP comprises partial or total thyroidectomy without further intervention. Management of PTC is the same but with the possible addition of radioactive ablation due to the increased malignant potential. This is the first report of bilateral NIFTP lesions and bilateral papillary microcarcinomas co-occurring together in the same patient, so management was challenging. The decision was made to give the patient low dose radioactive iodine ablation and continue monitoring. Ultrasound of the neck follow up 6 months later showed no residual thyroid tissue or local recurrence.

Conclusion

Although rare, NIFTP can co-occur with PTC. Bilateral NIFTP with bilateral PTC is extremely rare. Surgeons and pathologists need to be aware of this rare entity that can co-occur in both thyroid lobes. Total thyroidectomy is the definitive treatment. Post-surgery surveillance is important and follow up needs to be watchful for any recurrence or metastasis.

Updates in the Pathologic Classification of Thyroid Neoplasms: A Review of the World Health Organization Classification

Advances in medical sciences and evidence-based medicine have led to momentous changes in classification and management of thyroid neoplasms. Much progress has been made toward avoiding overdiagnosis and overtreatment of thyroid cancers. The new 2017 World Health Organization (WHO) classification of thyroid neoplasms updated the diagnostic criteria and molecular and genetic characteristics reflecting the biology and behavior of the tumors, and newly introduced the category of borderline malignancy or uncertain malignant potential. Some neoplasms were subclassified, renamed, or redefined as a specific entity. This review introduces changes in the fourth edition WHO classification of thyroid tumors and updates the contemporary diagnosis and classification of thyroid tumors. We also discuss several challenges with the proposal of new diagnostic entities, since they have unique histopathologic and molecular features and clinical relevance.

Noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP): a 13-year retrospective review at Jordan University Hospital

OBJECTIVE

Noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP) is the term to describe what was previously known as encapsulated follicular variant of papillary thyroid carcinoma. This new paradigm shift was agreed upon by experts in the field. The objective of this study is to evaluate cases previously diagnosed as follicular adenomas, follicular variant of papillary thyroid carcinoma and hyperplastic nodules to be reclassified as NIFTP according to the new criteria. Furthermore, the clinical follow-up of these NIFTP cases is evaluated.

METHODS

This retrospective study reviewed potential NIFTP cases over the last 13 years, at Jordan University Hospital.

RESULTS

A total of 811 thyroid surgery reports were identified and revised to identify the potential NIFTP cases. The review yielded 173 cases identified as potential NIFTP cases. Further pathological slide review resulted in a revised diagnosis of 32 cases of NIFTP according to the new criteria. The NIFTP cases comprised 4% of the total number of thyroidectomy cases and 16.1% of the total pool of previously diagnosed papillary thyroid carcinoma cases at our institution. While 111 cases retained their original diagnosis. Follow-up showed that all patients are alive and well with no evidence of disease.

CONCLUSION

Patients with NIFTP are not uncommon and the diagnosis is made only after a thorough evaluation of excision. Therefore, initial conservative management of solitary thyroid nodules suspicious for NIFTP in the form of lobectomy is recommended to avoid unnecessary total thyroidectomies. Our follow-up of NIFTP cases is similar to all previous reports.

Malignancy is in the eye of the beholder: Pathologic diagnosis of challenging follicular neoplasms in the era of noninvasive follicular thyroid neoplasms with papillary-like nuclear features and immunohistochemical and molecular adjuncts

BACKGROUND

Classification of thyroid follicular neoplasms can be challenging for pathologists. Introduction of noninvasive follicular thyroid neoplasms with papillary-like nuclear features, the utilization of immunohistochemistry, and molecular analysis are all thought to be valuable diagnostic adjuncts. Our aim was to determine whether interobserver variability for follicular neoplasms has improved since the application of these adjuncts.

METHODS

One representative section from a cohort of follicular neoplasms previously proven difficult for pathologists were examined independently by 7 pathologists and assigned to 1 of 3 diagnostic categories (benign, neoplasms with papillary-like nuclear features, or malignant). This process was carried out separately 3 times: (1) after viewing hematoxylin and eosin stain slides, (2) hematoxylin and eosin stain in conjunction with immunohistochemistry, and (3) hematoxylin and eosin stain/immunohistochemistry in conjunction with molecular analysis. The interobserver variability and overall agreement were then calculated using the free-marginal kappa coefficient.

RESULTS

Agreement on hematoxylin and eosin stain was 57%, with a kappa coefficient of 0.36 (minimal agreement). The agreement improved slightly with the application of immunohistochemistry (kappa coefficient = 0.49 [weak agreement] and a percentage agreement 67%). The level of agreement decreased slightly after the addition of molecular analysis (kappa coefficient = 0.43 [weak agreement] and percentage agreement 62%).

CONCLUSION

Despite attempts to standardize the diagnostic criteria for neoplasms with papillary-like nuclear features and the utilization immunohistochemistry and molecular analysis, attaining pathologic consensus for difficult follicular neoplasms of the thyroid remains a challenge.

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.

Noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP): a new entity

Since its first official definition in 2016, the new histo-pathological entity of noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP) has attracted much interest among "thyroidologists" worldwide. This is a subset of encapsulated and noninvasive follicular variant papillary thyroid cancer, whose introduction had the intent of de-escalating treatment given its very low malignant potential, approaching to that of follicular adenomas. Many researchers focused on the possibility of preoperatively identifying NIFTP, and investigated their cyto-morphological and molecular characteristics; other ones explored histological and clinical-pathological NIFTP features. Although the majority of published studies confirmed that NIFTP are indolent lesions, some papers did question their low-risk nature. In this brief review, the main aspects of histology, cytology and molecular pathology of NIFTP are discussed based on the current literature.

Correlations between Molecular Landscape and Sonographic Image of Different Variants of Papillary Thyroid Carcinoma

Papillary thyroid carcinoma (PTC), the most common thyroid cancer, is predominantly driven by mutations in BRAF (primarily p. V600E) and RAS oncogenes. Ultrasound (US) examination provides significant diagnostic data in the management of thyroid nodules, as many sonographic features of thyroid lesions are correlated with the potential risk of thyroid carcinoma. The aim of the study was to analyze the current literature in regard to the potential associations between genetic landscape and sonographic features of PTC. Based on the current literature, sonographic features of PTCs correlate with their molecular drivers, particularly between tumors harboring BRAF^V600E versus activating RAS mutations, although many of these findings appear to be dependent on the tumor variant. Suspicious US findings, such as hypoechogenicity, spiculated/microlobulated margins, non-parallel orientation/taller-than-wide shape, and the presence of microcalcifications, are typical for PTC positive for BRAF^V600E mutations. On the contrary, tumors with RAS mutations are most frequently hypo- or isoechoic and ovoid-to-round in shape, with smooth margins and without calcifications. There are also some US features typical for PTCs harboring other mutations, including BRAF^K601E, RET/PTC rearrangements, PAX8-PPARγ, CTNNB1, and APC. However, further research is necessary, as some rare PTC variants still cannot be reliably analyzed due to the scarce published data.

Revised criteria for diagnosis of NIFTP reveals a better correlation with tumor biological behavior

The recent reclassification of a follicular variant of papillary thyroid carcinoma (FVPTC), subset as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), aims to avoid overtreatment of patients with an indolent lesion. The diagnosis of NIFTP has recently been revisited using more rigid criteria. This study presents histological and molecular findings and a long clinical follow-up of 94 FVPTC, 40 cases of follicular adenoma (FTA) and 22 cases of follicular carcinoma (FTC) that were classified before the advent of the NIFTP reclassification. All slides were reviewed using these rigid criteria and analysis of numerous sections of paraffin blocks and reclassified as 7 NIFTPs, 2 EFVPTCs, 29 infiltrative FVPTC (IFVPTCs), 57 invasive EFVPTC (I-EFVPTCs), 39 FTAs and 22 FTCs. Remarkably, EFVPTC and NIFTP patients were all free of disease at the end of follow-up and showed no BRAF mutation. Only one NIFTP sample harbored mutations, an NRAS Q61R. PAX8/PPARG fusion was found in I-EFVPTCs and FTC. Although additional studies are needed to identify a specific molecular profile to aid in the diagnosis of lesions with borderline morphological characteristics, we confirmed that the BRAF V600E mutation is an important tool to exclude the diagnosis of NIFTP. We also show that rigorous histopathological criteria should be strongly followed to avoid missing lesions in which more aggressive behavior is present, mainly via the analysis of capsule or vascular invasion and the presence of papillary structures.