Papillae, psammoma bodies, and/or many nuclear pseudoinclusions are helpful criteria but should not be required for a definitive cytologic diagnosis of papillary thyroid carcinoma: An institutional experience of 207 cases with surgical follow up

BACKGROUND

Noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP) was introduced in 2016 replacing noninvasive follicular variant of papillary thyroid carcinoma, with recommendations to label them "noncancer." To avoid reducing risk of malignancy (ROM) and overdiagnosing NIFTP as malignant, some authors required restricted cytologic criteria (RC) for a definitive diagnosis of papillary thyroid carcinoma (PTC), including papillae, psammoma bodies. or ≥3 nuclear pseudoinclusions. Since then, NIFTP criteria have been revised, biologic behavior better understood, and incidence reported to be much lower than initially anticipated. This study examines the impact of RC on PTC cytologic diagnoses, ROM, and detection of clinically significant carcinomas (CSC).

MATERIALS AND METHODS

A total of 207 thyroid FNAs originally diagnosed as PTC and suspicious for PTC (SPTC) with surgical follow-up were evaluated. RC were retrospectively applied to cases as a requirement for diagnosing PTC, and cases that did not meet RC were reclassified as SPTC. ROMs and diagnostic accuracies of pre- and post-RC diagnoses were correlated with followup CSC.

RESULTS

RC were met in 118/142 (83%) and 20/65 (31%) of cases originally diagnosed as PTC and SPTC, respectively. Post-RC, 29% (19/65) of CSC originally diagnosed as SPTC were upgraded to PTC, and 17% (24/142) of CSC originally diagnosed as PTC were downgraded to SPTC. No NIFTPs were diagnosed as malignant.

CONCLUSIONS

RC should not be required for a definitive diagnosis of PTC when other nuclear features of PTC are diffuse and overt. Applying RC, however, helps the pathologist arrive at a more definitive diagnosis of PTC in suspicious cases.

Detailed fine needle aspiration cytopathology findings of noninvasive follicular thyroid neoplasm with papillary-like nuclear features with nuclear grading correlated to that of biopsy and Bethesda category and systematic review

BACKGROUND

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) poses diagnostic challenge in fine needle aspiration cytopathology (FNAC). We aimed first to document our FNAC Bethesda categories (BCs) for all of our NIFTPs and compare our findings with those in the literature with series containing at least 14 cases each.

METHODS

Cases with final histopathological diagnoses of NIFTP and their preoperative FNAC were retrieved from 2006 to 2022 and our cytopathological BCs were documented. Then the slides were re-reviewed in a blinded manner for detailed classification and the results of both the BCs and blinded reclassification were compared with series in the literature for both BCs and detailed cytopathological review of the cases.

RESULTS

Thyroid FNACs of 43 out of 86 patients with final NIFTP diagnoses were obtained. Females composed 72.1% (F/M: 31/12); mean age and mean tumor diameter was 47.6 (19-72 years) and 23.4 mm (7-60 mm), respectively. Totally 81.4% (35/43) were classified in the "indeterminate" diagnostic categories; namely 44.2% (19/43) were reported as atypia of undetermined significance (AUS; BC III), 20.9% (9/43) were follicular neoplasm (FN; BC IV), and 16.3% (7/43) were suspicious for malignancy (SM; BC V). No patient was diagnosed as positive for malignancy (BC VI), preoperatively. Detailed cytomorphologic reevaluation revealed heterogeneous cytopathologic findings and nuclear grade (especially nuclear enlargement, membrane irregularity and elongation) significantly increased with respect to BCs. Systematic review confirmed extremely heterogeneous cytomorphologic nature of NIFTP.

CONCLUSIONS

NIFTPs were categorized most frequently as AUS, followed by FN and SM on FNAC. Our re-review were not able to specify features solely unique to NIFTP alone but may distinguish these cases from classic papillary thyroid carcinoma.

Ultrasound features and risk stratification system in NIFT-P and other follicular-patterned thyroid tumors

OBJECTIVE

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFT-P) is an encapsulated follicular variant of papillary thyroid carcinoma (PTC) with nonaggressive clinical behavior. However, since its diagnosis is exclusively possible after surgery, it represents a clinical challenge. Neck ultrasound (US) shows good sensitivity and specificity in suggesting malignancy in thyroid nodules. However, little information is available about its ability in identifying NIFT-P.

DESIGN

The aim of this study was to evaluate the US features of NIFT-P, comparing them with other follicular-patterned thyroid tumors, and to test the ability of the main US risk stratification system (RSS) in identifying NIFT-P.

METHODS

We retrospectively evaluated 403 consecutive patients submitted to thyroid surgery, with positive histology for at least 1 nodule being NIFT-P, follicular variant of PTC (FV-PTC), follicular thyroid carcinoma (FTC), or follicular adenoma (FA).

RESULTS

The US features of NIFT-P (n = 116), FV-PTC (n = 170), FTC (n = 76), and FA (n = 90) were reported. Follicular variant of PTC and FTC more frequently showed irregular margins, presence of calcifications, "taller than wide" shape, and the absence of halo compared with NIFT-P. Furthermore, FTC and also FA were larger and more frequently hypoechoic than NIFT-P. Most cases (77%) showed an indeterminate cytology. Regardless of the US RSS considered, NIFT-P and FA were less frequently classified in the high-suspicious category compared with FV-PTC and FTC.

CONCLUSIONS

Ultrasound features of NIFT-P are frequently superimposable to those of nodules with low suspicion of malignancy. The NIFT-P is almost never classified in the high-suspicious category according to the main US RSS. Therefore, although the preoperative identification of NIFT-P remains a challenge, neck US can be integrated in the algorithm of management of nodules with indeterminate cytology, suggesting a possible conservative approach in those with low-suspicious features.

Total thyroidectomy can still remain the method of choice in some Bethesda III cases

BACKGROUND

The latest WHO classification of tumours of endocrine organs defines new units of borderline thyroid tumours (BTT). The aim of our study was to evaluate ultrasonographic and cytological features, mutation profile and surgery treatment in rare thyroid tumours.

METHODS

An analysis of 8 BTT out of 487 patients, who underwent thyroid surgery between June 2016 and June 2020. The definitive diagnosis was made postoperatively by extensive histopathological examination. Molecular genetic analysis of genes associated with thyroid oncology (BRAF, HRAS, KRAS, NRAS, TERT, TP53, fused genes) were performed from one FNAB, and 7 formalin-fixed paraffin-embedded (FFPE) samples.

RESULTS

BTT were found in a total of 8 patients (1.6%), with a predominance of men with respect to other operated patients. FNAB samples were classified in the Bethesda system as Bethesda I, Bethesda II and Bethesda III in one, four and three cases, respectively. Hemithyroidectomy and total thyroidectomy were performed equally in four patients. The histopathological diagnosis revealed non-invasive encapsulated follicular neoplasm with papillary-like nuclear features (NIFTP) in three patients, follicular tumour of uncertain malignant potential (FT-UMP) in three patients, well differentiated tumour of uncertain malignant potential (WDT-UMP) in one patient, and hyalinizing trabecular tumour (HTT) in one case. In NIFTP cases mutation in HRAS gene in one patient together with probable pathogenic variant in TP53 gene and in NRAS gene in two patients were detected. In HTT patient PAX8/GLIS3 fusion gene was detected.

CONCLUSION

The surgical treatment of BTT is necessarily individual influenced by preoperative clinical, ultrasonographic, cytological and molecular genetic findings, and the presence of other comorbidities.

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.

Non-invasive follicular thyroid neoplasm with papillary-like nuclear feature: clinical, pathological, and molecular update 5 years after the nomenclature revision

The term non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was proposed in 2016 and incorporated as a new entity in the World Health Organization (WHO) classification of tumours of endocrine organs in 2017. Since then, there has been debate regarding the histological criteria for the diagnosis, the need for molecular studies or the risk of lymph node metastasis or recurrence associated with this entity. Over the years, the concept of NIFTP evolved, now including both small (<1 cm) and large (>4 cm) tumours and oncocytic lesions. On the other hand, recent data on NIFTP in the setting of thyroid follicular nodular disease or frequent coexistence of malignant tumours raised concerns regarding the follow-up of these patients. Today, both pathologists and clinicians still face several challenges in the diagnosis, treatment, and follow-up of patients with NIFTP.

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.

Cytological Features of "Non-Invasive Follicular Tumour with Papillary like Nuclear Features" - A Single Institutional Experience in India

Background

The term noninvasive follicular tumor with papillary-like nuclear features (NIFTP) was introduced as a surrogate for noninvasive encapsulated follicular variant of papillary thyroid carcinoma with a defined set of histopathologic criteria. There are very few studies depicting the cytological cues for the diagnosis of NIFTP. The objective of the study was to determine the spectrum of cytological features in fine needle aspiration cytology (FNAC) smears of cases histopathologically diagnosed as NIFTP.

Methods

This was a retrospective cross-sectional study conducted over a duration of four years between January 2017 and December 2020. All surgically resected cases (n-21), who met the diagnostic criteria of NIFTP on histopathology and who underwent preoperative FNAC were included and reviewed in the study.

Results

Out of a total of 21 cases, at FNAC, diagnosis of benign, suspicious for malignancy, follicular variant of papillary thyroid carcinoma, and classic papillary thyroid carcinoma (PTC) was rendered in 14 (66.6%), 2 (9.5%), 2 (9.5%), and 3 (14.28%), respectively. Scanty cellularity was noted in 12 (57.1%) cases. Papillae, sheets, and microfollicles were seen in 1 (4.7%), 10 (47.6%), and 13 (61.9%) cases, respectively. Nucleomegaly, nuclear membrane irregularities, nuclear crowding, and overlapping were seen in 7 (33.3%), 9 (42.8%), and 9 (42.8%), respectively. Nucleoli, nuclear grooving, and inclusions were seen in 3 (14.2%) 10 (47.6%), and 5 (23.8%) cases, respectively.

Conclusion

At FNAC, NIFTP can be found in every category of The Bethesda System for Reporting Thyroid cytopathology (TBSRTC). Nuclear membrane irregularities, nuclear grooving, mild nuclear crowding, and overlapping were noted in a modest number of cases. However, the absence or rare occurrence of features such as papillae, inclusions, nucleoli, and metaplastic cytoplasm may help prevent an overdiagnosis of malignancy.

Clinicopathologic Characteristics and Postsurgical Follow-Up of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features in the Postnomenclature Revision Era

Background: Noninvasive encapsulated follicular variant papillary thyroid carcinoma (EFVPTC) was reclassified as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) in 2016. Most existing studies that examined outcomes included patients managed as EFVPTC and only retrospectively reclassified as NIFTP. This is the first study to evaluate the clinicopathologic, molecular, and surveillance characteristics of patients diagnosed with NIFTP at the time of surgery and managed based on this diagnosis. Methods: We performed a retrospective cohort study of consecutive cases diagnosed as NIFTP from June 2016 to October 2021 identified from electronic medical records at a large tertiary care institution. Patients with coexisting low-risk thyroid cancers ≥1.0 cm in size or any size aggressive histology were excluded, and review of demographic, clinical, imaging, cytologic, and molecular genetic data was performed. Initial care was delivered according to existing clinical guidelines, with a consensus institutional plan for five-year follow-up after surgery. Results: Among 79 patients with 84 nodules diagnosed as NIFTP after surgery, 83.5% (66/79) were women and the mean age was 51 years (range, 21-84). Mean NIFTP size was 2.4 cm (range 0.15-8.0). On ultrasound, the majority of nodules were categorized as thyroid imaging, reporting and data system TI-RADS 3 (55.3%, 42/76), and TI-RADS 4 (36.8%, 28/76). On cytology, they were typically diagnosed as Bethesda III (69.1%, 47/68) or Bethesda IV (23.5%, 16/68). Molecular testing was performed on 62 nodules, and molecular alterations were found in 93.5% (58/62). The most common alterations identified in NIFTP were RAS mutation (75.4%, 43/57), THADA fusion (12.3%, 7/57), and BRAF^K601E mutation (7.0%, 4/57). Fifty-two (65.8%) patients underwent lobectomy and 27 (34.2%) total thyroidectomy, and no patient received completion thyroidectomy. Twenty-one patients (26.5%) had coexisting papillary or follicular microcarcinoma. None of the patients received radioiodine ablation. On a mean follow-up of 28.5 months (range, 6-69 months), no structural or biochemical recurrences were observed. Conclusions: In this large cohort of patients with NIFTP diagnosed at the time of surgery and managed typically by lobectomy with no radioiodine ablation, no evidence of tumor recurrence was identified on a limited follow-up. This finding supports indolent clinical course of NIFTP.

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.  

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.

Molecular Characterization of Thyroid Follicular Lesions in the Era of "Next-Generation" Techniques

It is unequivocally recognized that thyroid nodules are frequently detected in the adult population and mostly characterized by benign lesions (up to 70% of them), with only 5%-15% malignant lesions. The evaluation of thyroid lesions with fine-needle aspiration cytology (FNAC) represents one of the first and most useful diagnostic tools in the definition of their nature. Despite the fact that the majority of thyroid lesions are correctly diagnosed as either benign (70%-75%) or malignant (5%-10%) entities, the remaining nodules (20%-25%) represent the "gray zone" of follicular lesions, which belong to indeterminate categories, according to the different classification systems. This indeterminate group of lesions includes both benign and malignant entities, which cannot be easily discriminate with morphology alone. In these last decades, the increasing role of molecular testings, feasibly performed on cytological material combined with the discoveries of specific genetic alterations in the field of thyroid pathology, has opened the pace to their more accurate and specific contribution on cytology. In fact, in 2015, in the revised management guidelines for patients with thyroid nodules and well-differentiated thyroid cancers (WDTCs), the American Thyroid Association (ATA) confirmed the performance of molecular testing in thyroid indeterminate cytology, and the same performance was addressed in recent update of the management of thyroid nodules in the second edition of the Bethesda system for reporting thyroid cytopathology (TBSRTC). In the current review, we discuss the role of molecular tests for the different thyroid diagnostic categories of the Bethesda system for reporting thyroid cytopathology, mostly focusing our attention on the follicular and indeterminate lesions.

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

CONTEXT.—

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

OBJECTIVES.—

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

DATA SOURCES.—

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

CONCLUSIONS.—

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

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.

Overview of the Ultrasound Classification Systems in the Field of Thyroid Cytology

The increasing application of ultrasound (US) in recent years has led to a greater number of thyroid nodule diagnoses. Consequently, the number of fine needle aspirations performed to evaluate these lesions has increased. Although the majority of thyroid nodules are benign, identifying methods to define specific lesions and tailor risk of malignancy has become vital. Some of the tools employed to stratify thyroid nodule risk include clinical factors, thyroid US findings, and reporting systems for thyroid cytopathology. Establishing high concordance between US features and cytologic diagnoses might help reduce healthcare costs by diminishing unnecessary thyroid procedures and treatment. This review aims to review radiology US classification systems that influence the practice of thyroid cytology.

Thyroid and Molecular Testing. Advances in Thyroid Molecular Cytopathology

Thyroid nodules are a common finding in the adult population including the fact that more than 50% of individuals, over the age of 60, have thyroid nodules. The majority have been mostly detected with ultrasonography and 10% by palpation. The majority of these nodules are benign, whereas 5–15% of them are malignant. The pre-operative diagnosis of cancer is a critical challenge in order to ensure that each patient can be treated with the best tailored management with a reduction of unnecessary surgery for benign lesions. Fine needle aspiration cytology (FNAC) represents the first and most important diagnostic tool for the evaluation of thyroid lesions. According to the literature, FNAC is able to render a conclusive diagnosis in up to 70–80% of all cases. For the remaining 20–30% of nodules, cytological diagnoses fall into the category of indeterminate lesions mostly due to the lack of specific morphological features. According to the Bethesda system for reporting thyroid cytopathology (TBSRTC), indeterminate lesions can be sub-stratified into three different subcategories including “atypia of undetermined significance/follicular lesion of undetermined significance-AUS/FLUS”; “follicular or Hürthle cell neoplasm/suspicious for follicular or Hürthle cell neoplasm-FN/SFN”; and “suspicious for malignancy-SFM”. Many of these indeterminate lesions undergo repetition or diagnostic lobectomy. Nonetheless, the majority of these cases will have a benign diagnosis due to the fact that the rate of cancer ranges between 6 and 30%. It stands to reason that the application of ancillary technique, mostly molecular testing, emerged as a critical additional tool for those thyroid indeterminate lesions. Since the early 1990s, material collected from cytological samples yields sufficient and adequate cells for the detection of point mutation or gene fusions. Nonetheless, the further availability of new sequencing technologies such as next-generation sequencing (NGS) has led to more comprehensive molecular applications adopted now in clinical use. The current review investigates the multiple advances in the field of molecular testing applied in thyroid cytology.

Clinicopathological parameters for predicting non-invasive follicular thyroid neoplasm with papillary features (NIFTP)

BACKGROUND

Criteria for the preoperative diagnosis of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) have not yet been confirmed. This study aimed to analyze differences in clinicopathological characteristics between follicular variant of papillary thyroid carcinoma (FVPTC) subtypes to determine which parameters are relevant in differentiating NIFTP from other variants.

METHODS

We retrospectively analyzed the records of 199 patients with a preoperative diagnosis of FVPTC who underwent thyroid surgery at Seoul St. Mary's Hospital (Seoul, Korea) from 2011 to 2015. Clinicopathological features were analyzed retrospectively via a complete review of medical charts and pathology reports of patients.

RESULTS

The NIFTP and invasive encapsulated FVPTC (EFVPTC) groups showed relatively benign features, with a majority of the patients categorized as Bethesda category III (25.8% and 25.6%, respectively) or IV (34.8% and 30.2%, respectively), while the infiltrative FVPTC group showed more malignant features, with more patients categorized as category V (28.6%) or VI (47.6%) (p < 0.001). BRAF ^V600E mutations were significantly less prevalent in the NIFTP group (0%) and invasive EFVPTC group (4.7%) compared with the infiltrative FVPTC group (34.9%) (p < 0.001). Multivariate analysis showed that absence of BRAF ^V600E mutation (OR 20.311, p = 0.004) and lymph node metastasis (odds ratio 10.237, p = 0.004) were significantly associated with NIFTP.

CONCLUSION

Although Bethesda category was a statistically significant factor in distinguishing FVPTC subtypes, it was not effective in conclusively distinguishing NIFTP and invasive EFVPTC. Absence of BRAF ^V600E mutation and lymph node metastasis are important features in distinguishing NIFTP from other subtypes.

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.

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.

The importance of risk of neoplasm as an outcome in cytologic-histologic correlation studies on thyroid fine needle aspiration

BACKGROUND

The introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) altered the practice of thyroid pathology and reduced the risk of malignancy (ROM) associated with the indeterminate categories in the Bethesda system for reporting thyroid cytopathology (TBSRTC). It has been proposed that the evaluation of the risk of neoplasm (RON) is important in cytologic-histologic correlation studies.

METHODS

A total of 5224 thyroid aspirates were performed at our institution during an 8-year period. Of the 1475 cases (28%) with surgical follow-up, the histologic diagnoses comprised benign non-neoplastic (BNN, n = 669), follicular adenoma (FA, n = 188), NIFTP (n = 42), papillary microcarcinoma (PMC) (n = 223), and malignant neoplasm excluding PMC (n = 353). The RON was calculated to include neoplasia with low risk biologic behavior (FA, NIFTP, PMC) and malignant neoplasms. In contrast, the ROM was reserved for malignant neoplasms excluding PMC.

RESULTS

The RON for each TBSRTC category was: nondiagnostic (ND) 38.3%, benign 20.9%, atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) 63.2%, follicular neoplasm or suspicious for follicular neoplasm (FN/SFN) 83.9%, suspicious for malignancy (SFM) 94%, and malignant 100%. The ROM excluding PMC was: ND 14%, benign 1.6%, AUS/FLUS 17.8%, FN/SFN 28.4%, SFM 84.4%, and malignant 99.5%.

CONCLUSIONS

The RON and ROM support the recommended management guidelines from TBSRTC for all categories, except for FN/SFN. Histopathologic follow-up of FN/SFN aspirates in our study contain a very high rate of neoplasm (83.9%), which might support the management preference of conservative surgery.

Impact of Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features on Revised Bethesda System Malignancy Rates at a Single Institution

BACKGROUND

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) standardizes thyroid cytopathology reporting in six tier diagnostic categories. In recent years, noninvasive encapsulated follicular variant of papillary thyroid carcinoma was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). This study examines the impact of NIFTP on the BSRTC risk of malignancy (ROM).

METHODS

This was a retrospective review of prospectively collected data from 565 patients who underwent fine needle aspiration and thyroidectomy at a single institution. ROM for each Bethesda category was analyzed and calculated with NIFTP classified as a malignant and nonmalignant lesion. Absolute and relative differences between ROM were compared.

RESULTS

Of 565 patients, 19 were Bethesda I, 159 were Bethesda II, 178 were Bethesda III, 46 were Bethesda IV, 42 were Bethesda V, and 121 were Bethesda VI. ROM differences with NIFTP classified as malignant versus nonmalignant for each class were as follows: Bethesda I, no change; Bethesda II, 18%-14%; Bethesda III, 55%-48%; Bethesda IV, 50%-35%; Bethesda V, 93%-91%; and Bethesda VI, 99%-98%. Absolute ROM differences for each category were as follows: Bethesda I, 0%; Bethesda II, 4%; Bethesda III, 7%; Bethesda IV, 15%; Bethesda V, 2%; and Bethesda VI, 1%.

CONCLUSIONS

A decreasing trend in absolute and relative ROM was seen in Bethesda II, III, and IV categories; however, exclusion of NIFTP as a malignant lesion did not significantly alter the ROM of BSRTC categories. Surgeons should assess their respective institution's experiences with NIFTP and the BSRTC.

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.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features and the risk of malignancy in The Bethesda System for the Reporting of Thyroid Cytopathology

INTRODUCTION

The Bethesda System for the Reporting of Thyroid Cytopathology (TBSRTC) is used to categorize and diagnose thyroid nodules by fine needle aspiration biopsy (FNAB). Each category in TBSRTC is associated with an estimated risk of malignancy (ROM). A subset of noninvasive encapsulated follicular variant of papillary thyroid carcinoma (niEFVPTC) was reclassified as a nonmalignant tumor: noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). We studied the impact of this reclassification on the reported ROM in TBSRTC.

MATERIAL AND METHODS

We searched our institutional files for thyroid FNAB with surgical follow-up. ROM for each TBSRTC category was calculated. Subsequently, cases of niEFVPTC were reviewed and reclassified as NIFTP, if appropriate. ROM for each category was then recalculated after the reclassification.

RESULTS

Twenty-six NIFTP were identified; the corresponding FNABs were distributed among all six TBSRTC categories. The majority of NIFTP FNAB were in the AUS/FLUS and suspicious for malignancy (SUSP) categories, 12 (46.2%) and 8 (30.8%), respectively. While the ROM changed for all diagnostic categories, the greatest change in ROM after reclassification was seen in these two categories. Absolute ROM for AUS/FLUS decreased from 25.0% to 21.0% and SUSP, from 71.7% to 58.3%, changes that were statistically significant.

CONCLUSIONS

The reclassification of niEFVPTC to NIFTP has significantly impacted the ROM in the TBSRTC at our institution. While there was a decrease in ROM for all categories, the greatest reduction to ROM was in the categories of AUS/FLUS and FN. These changes to the ROM should help guide surgical approach moving forward.

Can cytology and the Thyroid Imaging, Reporting, and Data System (TI-RADS) identify noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) before surgery?

INTRODUCTION

In 2017, the American College of Radiology (ACR) created the Thyroid Imaging, Reporting, and Data System (TI-RADS) to select thyroid nodules for fine-needle aspiration (FNA). The objective of this study is to find out whether ACR TI-RADS is useful in triaging thyroid follicular cells with papillary-like nuclear features obtained by FNA to determine the extent of surgery.

MATERIAL AND METHODS

The grayscale ultrasound of 76 noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 41 encapsulated (E), and 79 infiltrative (I) follicular variant (FV) of papillary thyroid carcinoma (PTC) were reviewed and assigned TI-RADS points and then suspicion levels.

RESULTS

Of the 39 tumors with high suspicion level, 32 were IFVPTC, and seven were EFVPTC. Of the 137 tumors with moderate suspicion level, 47 were IFVPTC, 34 were EFVPTC, and 56 were NIFTP. Of the 19 tumors with mild suspicion level, all were NIFTP. The only tumor with no suspicion was an NIFTP. IFVPTC had a significantly higher suspicion level than EFVPTC and NIFTP (P < 0.0001). The difference in suspicion level between EFVPTC and NIFTP is not statistically significant. None of the cases of NIFTP in the study had a high suspicion level.

CONCLUSIONS

The study demonstrates that cytology interpreted in the context of ACR TI-RADS suspicion levels can separate NIFTP from many IFVPTC and a few EFVPTC with overt invasion. PTC could be diagnosed in cytology if cells with papillary-like nuclear features derived from TR5 nodules. The nodules with TR4 or less that yield similar cells require surgical pathology to diagnose FVPTC with microscopic capsular or vascular invasions.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: a problematic entity

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a borderline thyroid tumour formerly known as noninvasive encapsulated follicular variant of papillary thyroid carcinoma. The prevalence of NIFTP is estimated at 4.4-9.1% of all papillary thyroid carcinomas worldwide; however, the rate of occurrence of NIFTP is eight times lower in Asian countries than in Western Europe and America. At the molecular level, NIFTP is characterised by the lack of BRAF V600E and BRAF V600E-like mutations or other high-risk mutations (TERT, TP53), and a high rate of RAS mutations, which is similar to other follicular-pattern thyroid tumours. The diagnosis of NIFTP can only be made after histological examination of the entire tumour removed during surgery, and is based on strictly defined inclusion and exclusion criteria. Although the diagnosis is postoperative, the combination of certain findings of preoperative tests including ultrasonography, cytology, and molecular testing may raise suspicion of NIFTP. These tumours can be effectively treated by lobectomy, although total thyroidectomy remains an option for some patients. Radioactive iodine and thyroid stimulating hormone suppression therapy are not required. NIFTP has an extremely good prognosis, even when treated conservatively with lobectomy alone. Nevertheless, it cannot be considered as a benign lesion. The risk of adverse outcomes, including lymph node and distant metastases, is low but not negligible.

Long-term progression of non-invasive follicular thyroid neoplasm with papillary-like nuclear features: A single-center retrospective study of the French Marne-Ardennes thyroid cancer registry

CONTEXT

Non-invasive forms of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) were reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in order to reduce overtreatment. A few studies showed neck lymphadenopathy at diagnosis, or even distant metastasis in patients with NIFTP.

OBJECTIVE

Our aim was to report the frequency, clinical features and long-term progression of histologically confirmed NIFTP, using data from the French Marne-Ardennes thyroid cancer registry, and to compare findings against FVPTC.

METHODS

This was a retrospective study on data for follicular variant of PTC (FVPTC) diagnosed between 1975 and 2015 obtained from the specialized Marne-Ardennes thyroid cancer registry. Pathology reports were used to select appropriate cases from a large series, and FVPTC specimens were reviewed by endocrine pathologists. Strict diagnostic criteria were used for reclassification as NIFTP.

RESULTS

In total, 115 cases were reviewed histologically out of 383 cases of FVPTC. Sixty-five met all criteria for NIFTP and were consequently reclassified. Incidence of NIFTP was 16.9% of cases of FVPTC. Fifty patients were women (76.9%); median age was 47 years. Mean NIFTP size was 2.6 cm. There were no significant differences in age, gender or tumor size between NIFTP and FVPTC. Fifty patients underwent total thyroidectomy and 15 lobectomy. There were no lymph node metastases at diagnosis, and none of the patients (N=17) who underwent central and/or lateral neck dissection had positive findings on microscopic examination. 46 patients (70.8%) received radioiodine (RAI). Patients were followed up for 1.9-27.3 years (median 14.6 years) after initial treatment. All patients remained in complete remission during follow-up.

CONCLUSION

Consistently with previous studies, our results showed the indolent course of NIFTP and that risk of recurrence after complete resection is very low (zero in our cohort), even when size is ≥4cm and in absence of adjuvant RAI treatment. Prospective studies are needed to confirm those results.

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.

Ancillary molecular testing of indeterminate thyroid nodules

Cytological specimens from thyroid nodules are increasingly being adopted as the first available material for cost effectively managing patients in the era of personalized medicine. Cytology aspirates not only play a central role in providing accurate diagnoses, but are also being collected for ancillary molecular testing. Molecular analysis, including the evaluation of somatic mutations and other genomic alterations, has accordingly become well integrated in the cytological workup of thyroid lesions. Appropriately handled thyroid cytology preparations provide well-preserved and adequately cellular material with improved DNA/RNA quantity. The recent publication of the 2nd edition of The Bethesda System for Reporting Thyroid Cytopathology and the American Thyroid Association guidelines confirm the relevant role of molecular testing in the management of the different subcategories of indeterminate thyroid lesions. This review discusses the role of molecular testing for indeterminate thyroid nodules, including the recent introduction of the noninvasive, encapsulated follicular variant of papillary thyroid carcinoma (FVPTC), known also as noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP).

The Role of Molecular Testing for the Indeterminate Thyroid FNA

Thyroid nodules are common in the adult population where a majority are benign and only 4.0% to 6.5% are malignant. Fine needle aspiration (FNA) is a key method used in the early stages to evaluate and triage patients with thyroid nodules. While a definitive cytological diagnosis is provided in more than 70–75% of all thyroid FNA cases, the group of indeterminate lesions offers a challenge in terms of interpretation and clinical management. Molecular testing platforms have been developed, are recognized as an option by the 2015 American Thyroid Association Guidelines, and are frequently used in conjunction with FNA as an integral part of the cytologic evaluation. In this review, the utility of molecular testing options for nodules assigned to the group of indeterminate thyroid FNAs is described.

Systematic Review and Meta-analysis of the Impact of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) on Cytological Diagnosis and Thyroid Cancer Prevalence

A re-named diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) likely impacts the prevalence of thyroid cancer and risk of malignancy in populations based on the established Bethesda System of Reporting Thyroid Cytopathology (TBSRTC). This study was done to investigate the prevalence and cytological distribution of NIFTP. PRISMA guided systematic review was done from a database search of Pubmed, EMBASE, and Medline using the search terms "non-invasive follicular thyroid neoplasm with papillary-like nuclear features", "non-invasive follicular variant of papillary carcinoma", "niftp", and "Bethesda" until November 2018. Original articles with surgically proven diagnoses of NIFTP using strict NIFTP criteria were included. Twenty-nine studies with 1563 cases of NIFTP were included. The pooled prevalence of NIFTP in cases which would be classified previously as the follicular variant of papillary thyroid cancer (FVPTC) and papillary thyroid cancer (PTC) were 43.5% (95% CI 33.5-54.0%) and 4.4% (95% CI 2.0-9.0%) respectively. The pooled TBSRTC distribution of cases diagnosed as NIFTP was: from the non-diagnostic category 3.6% (95% CI 2.4-5.3%), benign 10.0% (95% CI 7.2-13.6%), AUS/FLUS 34.2% (95% CI 28.2-40.8%), FN/SFN 22.7% (95% CI 17.2-29.4%), suspicious for malignancy 22.4% (95% CI 17.7-27.9%), and malignant 7.5% (95% CI 4.2-12.9%). While a significant reduction in FVPTC prevalence is anticipated, a modest reduction of PTC prevalence is also expected with adoption of the NIFTP terminology that would be distributed mainly among lesions classified as indeterminate thyroid nodules. Further studies are needed to identify unique clinical characteristics of these lesions preoperatively.

Comprehensive analysis for diagnosis of preoperative non-invasive follicular thyroid neoplasm with papillary-like nuclear features

OBJECTIVE

The current paradigm in the treatment of patients with non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a diagnostic lobectomy rather than complete thyroidectomy and postoperative radioiodine treatment. Consequently, preoperative diagnosis of NIFTP is considered to be important.

METHODS

We performed the comprehensive analysis for diagnosis of preoperative 20 NIFTPs in comparison with 41 invasive encapsulated follicular papillary thyroid carcinomas (I-EFVPTCs) using the Korean Thyroid Imaging Reporting and Data System (K-TIRADS), Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), and molecular analysis for BRAF and RAS mutations.

RESULTS

K-TIRADS 3 was identified as the most common sonographic diagnosis in both NIFTP and I-EFVPTC. Unlike I-EFVPTC, K-TIRADS 5 was not identified in NIFTP. AUS/FLUS was the most common cytopathological diagnosis and none of the cases were classified as malignant category in both groups, although the difference in distribution was not significant between the groups. BRAF mutation was not found in NIFTP but was present in 9.8% of cases in I-EFVPTC. The frequency of RAS mutation in I-EFVPTCs was twice as high as that of NIFTP. Wild-type BRAF and RAS in NIFTP was significantly higher than I-EFVPTC.

CONCLUSION

The existence of overlapping features between the groups was evident, hence conclusive distinction between radiology, cytology and molecular analysis could not be achieved. Apparently, the diagnosis of NIFTP based on comprehensive analysis was not confirmable but could perceive or at least favor the diagnosis of NIFTP.

Ultrasound characteristics of thyroid nodules facilitate interpretation of the malignant risk of Bethesda system III/IV thyroid nodules and inform therapeutic schedule

Background

This study was designed to explore whether ultrasound of thyroid nodules facilitates the interpretation of the malignant risk of Bethesda III/IV thyroid nodules to inform further therapies.

Methods

We reviewed patient records in which the results of ultrasound‐guided fine‐needle aspiration (US‐FNA) were classified by the Bethesda III/IV in our institution between January 2016 and June 2018. Studies were retrieved from PubMed, Cochrane Central Register of Controlled Trials, ISI Web of Science, Science Direct, Wiley Online Library, EMBASE, China National Knowledge Infrastructure, WanFang, and Chinese VIP. The odds ratio (OR) was used to measure associations between risk factors and thyroid nodule malignancy.

Results

Fifty‐nine cases of Bethesda III/IV with corresponding surgeries were included, and the malignancy risk was 54.2%. Meta‐analysis revealed irregular borders, solitary nodules, hypoechogenicity, microcalcifications, and being taller than wide, all of which increased the malignancy risk of thyroid nodules. Combined ORs for these factors were 4.08 (95% CI: 2.34‐7.14, P < .001), 2.18 (95% CI: 1.39‐3.42, P = .001), 2.02 (95% CI: 1.35‐3.01, P = .001), 3.21 (95% CI: 2.26‐4.56, P < .001), and 4.35 (95% CI: 3.07‐6.15, P < .001), respectively.

Conclusion

As the risk of malignancy for papillary thyroid carcinoma (PTC) is high, when any one of the five ultrasound features of malignancy were confirmed, repeated FNA is recommended to confirm PTC‐type malignancy, even though nodules were Bethesda III/IV classification. However, repeated FNA should be avoided when none of these ultrasound features are identified because repeated FNA does not contribute to identifying non‐PTC type malignancies, such as follicular thyroid carcinoma and poorly differentiated thyroid carcinoma.

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

Advances in our understanding of thyroid lesions, especially those entities with an indolent behavior, has led clinicians to question the most appropriate surgical management of such thyroid nodules. Several studies have shown that the non-invasive encapsulated follicular variant of papillary thyroid carcinomas (NI-EFVPC) exhibits poor histopathologic diagnostic reproducibility and have been over-treated as conventional thyroid cancer. In 2015, an international thyroid working group re-evaluated NI-EFVPC and its diagnostic criteria. The new terminology of "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was accordingly introduced to replace NI-EFVPC. The literature has emphasized that NIFTPs are biologically similar to follicular adenomas lacking lymph node metastases and/or recurrence. While the definition of NIFTP is based on specific morphological parameters, recent studies have questioned whether the criterion allowing less than 1% of true papillae should be revised to a total absence of papillae. The motivation for this revision is the rare finding, in some studies, of lymph nodes with metastatic NIFTP. This review evaluates the existing published series of NIFTP cases, clinical consequences of NIFTP, and emerging changes in the diagnostic criteria for NIFTP. The introduction of NIFTP has resulted in significant impact on the clinical management of thyroid nodules. Recent revisions in the morphological criteria for NIFTP emphasize the need to adhere to very stringent histomorphologic criteria when making a diagnosis of NIFTP. The adoption of NIFTP terminology instead of NI-EFVPC is associated with conservative lobectomy without radioactive iodine treatment in the majority of cases.

Non-invasive follicular thyroid neoplasm with papillary-like nuclearfeatures (NIFTP): a review and update

BACKGROUND

The nomenclature "Non-invasive Follicular Neoplasm with Papillary-like Nuclear Features (NIFTP)" was introduced in 2016. While NIFTP differs from classic papillary thyroid carcinoma (PTC) in imaging, cytomorphology, histology, molecular profile, treatment, follow up, outcome, and behavior, it largely overlaps with follicular variant of PTC at imaging and cytomorphology. Herein, we review the literature for better understanding NIFTP, and its impact on patient care.

METHODS

The English literature was thoroughly evaluated with the key word of "Noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP)".

OBSERVATIONS

NIFTP presents as a thyroid nodule. On imaging, it is a round-to-oval, well circumscribed mass with solid internal content. Aspirated material shows a microfollicular pattern with focal nuclear features of PTC mostly reported in categories 3-5 of the Bethesda System for Reporting Thyroid Cytology (TBRSTC). NIFTP has decreased risk of malignancy in TBRSTC categories 3-6. Histologic examination of NIFTP reveals an encapsulated neoplasm with follicular pattern and nuclear features of PTC with no capsular or vascular invasion. No papillary structure, atypia, or mitosis is present. In contrast to PTC, only 4% of NIFTP cases harbor a BRAF mutation. Because NIFTP carries an excellent prognosis and indolent behavior, the tumor behavior was changed from malignant to a neoplasm with tumor with extremely indolent behavior. The recommended treatment is lobectomy with no further ablation therapy. Until better understanding of NIFTP, patient's follow up should be occasionally performed by neck ultrasonography and serum thyroglobulin measurement.

CONCLUSION

NIFTP carries an excellent prognosis. It is critical for both clinicians and patients to be aware of extremely indolent behavior of NIFTP in order to prevent unnecessary, aggressive treatment.

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

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is an encapsulated or clearly delimited, noninvasive neoplasm with a follicular growth pattern and nuclear features of papillary thyroid carcinoma (PTC). It is considered a 'pre-malignant' lesion of the RAS-like group. Ultrasonography (US), cytology and molecular tests are useful to suspect thyroid nodules that correspond to NIFTP but there is wide overlap of the results with the encapsulated follicular variant of PTC (E-FVPTC). In these nodules that possibly or likely correspond to NIFTP, if surgery is indicated, lobectomy is favored over total thyroidectomy. The diagnosis of NIFTP is made after complete resection of the lesion by observing well-defined criteria. In the case of patients who received the diagnosis of FVPTC and whose pathology report does not show findings of malignancy (lymph node metastasis, extrathyroidal invasion, vascular/capsular invasion), if the tumor was encapsulated or well delimited, the slides can be revised by an experienced pathologist to determine whether the diagnostic criteria of NIFTP are met, but special attention must be paid to the adequate representativeness of the capsule and tumor. Since NIFTP is not 'malignant', tumor staging is not necessary and patients are not submitted to thyroid cancer protocols or guidelines. We believe that patients with NIFTP without associated malignancy and without nodules detected by US of the remnant lobe (if submitted to lobectomy) can be managed like those with follicular adenoma.

Comparative Diagnostic Accuracy of Contrast-Enhanced Ultrasound and Shear Wave Elastography in Differentiating Benign and Malignant Lesions: A Network Meta-Analysis

Background: We performed a network meta-analysis to compare the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) and shear wave elastography (SWE) in differentiating benign and malignant lesions in different body sites.

Methods: A computerized literature search of Medline, Embase, SCOPUS, and Web of Science was performed using relevant keywords. Following data extraction, we calculated sensitivity, specificity, positive likelihood ratio (LR), negative LR, and diagnostic odds ratio (DOR) for CEUS, and SWE compared to histopathology as a reference standard. Statistical analyses were conducted by MetaDiSc (version 1.4) and R software (version 3.4.3).

Results: One hundred and fourteen studies (15,926 patients) were pooled in the final analyses. Network meta-analysis showed that CEUS had significantly higher DOR than SWE (DOR = 27.14, 95%CI [2.30, 51.97]) in breast cancer detection. However, there were no significant differences between CEUS and SWE in hepatic (DOR = −6.67, 95%CI [−15.08, 1.74]) and thyroid cancer detection (DOR = 3.79, 95%CI [−3.10, 10.68]). Interestingly, ranking analysis showed that CEUS achieved higher DOR in detecting breast and thyroid cancer, while SWE achieved higher DOR in detecting hepatic cancer. The overall DOR for CEUS in detecting renal cancer was 53.44, 95%CI [29.89, 95.56] with an AUROC of 0.95, while the overall DOR for SWE in detecting prostate cancer was 25.35, 95%CI [7.15, 89.89] with an AUROC of 0.89.

Conclusion: Both diagnostic tests showed relatively high sensitivity and specificity in detecting malignant tumors in different organs. Network meta-analysis showed that CEUS had higher diagnostic accuracy than SWE in detecting breast and thyroid cancer, while SWE had higher accuracy in detecting hepatic cancer. However, the results were not statistically significant in hepatic and thyroid malignancies. Further head-to-head comparisons are needed to confirm the optimal imaging technique to differentiate each cancer type.

Cytomorphology of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features and the Impact of New Nomenclature on Molecular Testing

The re-naming of noninvasive follicular variant papillary thyroid cancer to the apparently non-malignant, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) impacts the prevalence of malignancy rates, thereby affecting mutation frequency in papillary thyroid cancer. Preoperative assessment of such nodules could affect management in the future. The original publications following the designation of the new nomenclature have been extensively reviewed. With the adoption of NIFTP terminology, a reduction in the follicular variant of papillary thyroid cancer (FVPTC) prevalence is anticipated, as is a modest reduction of papillary thyroid cancer (PTC) prevalence that would be distributed mainly across indeterminate thyroid nodules. Identifying NIFTP preoperatively remains challenging. RAS mutations are predominant but the presence of BRAF V600E mutation has been observed and could indicate inclusion of the classical PTC. The histological diagnosis of NIFTP to designate low-risk encapsulated follicular variant papillary thyroid cancers (EFVPTCs) would impact malignancy rates, thereby altering the mutation prevalence. The histopathologic criteria have recently been refined with an exclusion of well-formed papillae. The preoperative identification of NIFTP using cytomorphology and gene testing remains challenging.

Cytological features of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

INTRODUCTION

The noninvasive encapsulated follicular variant of papillary carcinoma (EFVPC) was recently renamed a noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) because of its unique genetic alterations and biological behavior. The objective of this report is to help cytopathologists and cytotechnologists improve diagnostic accuracy and determine the need for cytogenetic studies during adequacy evaluation of thyroid fine-needle aspirations.

MATERIALS AND METHODS

Fifty-five cases of surgery-proven noninvasive EFVPC with corresponding cytology material were reviewed. These cases were collected over 17 years, from 1999 to 2016.

RESULTS

Thirty-four of 55 (61.8%) cases were diagnosed as follicular neoplasm or suspicious for follicular neoplasm on cytology. Eighty to ninety percent of cases showed scant colloid, cellular smears with small clusters of follicular cells with nuclear atypia including enlarged nuclei, oval-shaped nuclei, nuclear grooves, mild chromatin powdering, and rare nuclear pseudo-inclusions.

CONCLUSIONS

NIFTP has unique features: cytologically similar to follicular neoplasms, and nuclear atypia falling between atypia of undetermined significance (category III) and suspicious for/and papillary thyroid carcinoma (category V/VI) (The Bethesda System for Reporting Thyroid Cytopathology).

Thyroid nodule size calculated using ultrasound and gross pathology as predictors of cancer: A 23-year retrospective study

BACKGROUND

Thyroid nodules are very common. Ultrasound (US) and fine needle aspiration (FNA) are both integral in cancer screening. This study investigated the concordance between thyroid nodule sizes measured by US and gross pathologic examination and their relationship with malignancy.

METHODS

A retrospective design was used to select consecutive patients with proven carcinoma of the thyroid. The number and maximum diameter of nodules, rates and types of malignancy, as well as predictors of malignancy were determined.

RESULTS

The 10 944 patients examined had 15 283 thyroid nodules, 44.6% of which were malignant. Of the 4449 nodules sampled by FNA and the 8748 not sampled by FNA, 76.5% and 30.5% were malignant, respectively. The sensitivity, specificity, positive and negative predictive values (NPVs), and overall accuracy of FNA based on final pathology were 97.9%, 96.3%, 98.8%, 93.5%, and 97.5%, respectively. Nodule sizes determined by US were comparable with most nodules having either the same size range (n = 2959, 77.7%) or differing only by one size range (n = 770, 20.5%).

CONCLUSIONS

Thyroid nodule size is inversely related to malignancy risk, as larger nodules have lower malignancy rates. Nodule size estimated by US shows relatively good correlation with final pathologic size. However, thyroid nodules should undergo FNA regardless of size. If the FNA is not benign, nodule size should influence therapeutic decision making.

Update on: proteome analysis in thyroid pathology - part II: overview of technical and clinical enhancement of proteomic investigation of the thyroid lesions

INTRODUCTION

An accurate diagnostic classification of thyroid lesions remains an important clinical aspect that needs to be addressed in order to avoid 'diagnostic' thyroidectomies. Among the several 'omics' techniques, proteomics is playing a pivotal role in the search for diagnostic markers. In recent years, different approaches have been used, taking advantage of the technical improvements related to mass spectrometry that have occurred. Areas covered: The review provides an update of the recent findings in diagnostic classification, in genetic definition and in the investigation of thyroid lesions based on different proteomics approaches and on different type of specimens: cytological, surgical and biofluid samples. A brief section will discuss how these findings can be integrated with those obtained by metabolomics investigations. Expert commentary: Among the several proteomics approaches able to deepen our knowledge of the molecular alterations of the different thyroid lesions, MALDI-MSI is strongly emerging above all. In fact, MS-imaging has also been demonstrated to be capable of distinguishing thyroid lesions, based on their different molecular signatures, using cytological specimens. The possibility to use the material obtained by the fine needle aspiration makes MALDI-MSI a highly promising technology that could be implemented into the clinical and pathological units.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: An interobserver study of key cytomorphological features from a large academic medical centre

OBJECTIVE

Because of the indolent nature of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) and potential requisite for a more conservative treatment, it is crucial to identify features of this entity preoperatively. Our group recently published findings that there are several cytomorphological features that may be used as clues to distinguish NIFTP, papillary thyroid carcinoma (PTC) and follicular adenoma (FA) on fine needle aspiration. Therefore, we aimed to determine the interobserver reproducibility of these findings.

METHODS

Presurgical fine-needle aspiration slides from NIFTP (n = 30), classic PTC (n = 30) and FA (n = 30) collected from 1/2013-8/2016 were reviewed by seven cytopathologists blindly. Presence of selected cytomorphological features was recorded and compared to determine percent agreement and inter-rater reliability among study cytopathologists using Gwet's AC1 statistics.

RESULTS

For all the cytomorphological features, the overall percent agreement amongst the pathologists ranged between 65.1% and 86.8% (Gwet's AC1 0.30-0.80). There was substantial or almost perfect agreement (Gwet's AC1 > 0.60) in seven cytomorphological features in the classic PTC group, in six features in the NIFTP group and in five features in the FA group. There were no features with poor agreement (Gwet's AC1 < 0.0).

CONCLUSIONS

The current study supports the reproducibility of our previous findings. The high level of agreement amongst pathologists for these groups, and particularly the NIFTP group, supports the notion that when viewed in combination as a cytological profile, these cytomorphological features may assist the cytopathologist in raising the possibility of NIFTP preoperatively. This can potentially aid clinicians in deciding whether more conservative treatment may be appropriate.

AHNS Series: Do you know your guidelines? AHNS Endocrine Section Consensus Statement: State-of-the-art thyroid surgical recommendations in the era of noninvasive follicular thyroid neoplasm with papillary-like nuclear features

The newly introduced pathologic diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) will result in less bilateral thyroid surgery as well as deescalation in T4 suppressive and radioactive iodine treatment. Although, NIFTP is a nonmalignant lesion that has nuclear features of some papillary malignancies, the challenge for the surgeon is to identify a lesion as possibly NIFTP before the pathologic diagnosis. NIFTP, due to its reduction of overall rates of malignancy, will result in the initial surgical pendulum swinging toward lobectomy instead of initial total thyroidectomy. This American Head and Neck Society endocrine section consensus statement is intended to inform preoperative evaluation to attempt to identify those patients whose final pathology report may ultimately harbor NIFTP and can be offered a conservative surgical plan to assist in cost-effective, optimal management of patients with NIFTP.

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

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

A user's guide to non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

The term non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was recently introduced to replace a subset of follicular variant of papillary thyroid carcinoma (FVPTC). The goal of this change was to promote more conservative management of these tumours and spare patients the psychological burden of a cancer diagnosis. The histological diagnosis of NIFTP is stringent: the tumour needs to demonstrate encapsulation or circumscription, a purely follicular architecture and the presence of nuclear features of papillary thyroid carcinoma, while lacking capsular and vascular invasion, a significant component of solid growth and high-grade features (increased mitotic activity and necrosis). In order to ensure that these inclusion and exclusion criteria are met, the tumour must be sampled extensively, with the entire capsule/periphery submitted in all cases. When sampled by fine-needle aspiration, NIFTP is usually classified within the indeterminate categories of the Bethesda System for Reporting Thyroid Cytopathology. NIFTP is characterized genetically by frequent RAS mutations, although rarely other alterations, such as the BRAF K601E mutation and gene rearrangements in PPARG or THADA, may occur. In this review, we will examine the history of FVPTC and the findings and factors that culminated in the introduction of the NIFTP terminology. A discussion will follow with the histological, cytological and molecular characteristics of NIFTP. We will conclude by considering the potential impact of the introduction of the NIFTP terminology.

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

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

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: Can Cytology Face the Challenge of Diagnosis in the Light of the New Classification?

OBJECTIVES

To assess the cytological findings of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), conventional papillary thyroid carcinomas (C-PTC), and invasive follicular variants of papillary thyroid carcinomas (IFV-PTC) to determine if there are cytological differences between groups.

STUDY DESIGN

We have reviewed all thyroid fine-needle aspiration cytology samples diagnosed between 2000 and 2017. We have included all NIFTP cases (n = 6) and randomly selected cases of C-PTC (n = 14) and IFV-PTC (n = 8).

RESULTS

Comparing NIFTP and C-PTC cases, NIFTP cases showed significantly less papillary or pseudopapillary architecture, more bidimensional groups and microfollicles, and less tridimensionality, giant cells, and nuclear folds. We observed a trend towards significance for smear cellularity and amount of cytoplasm. Presence of nuclear folds was the only significant difference between NIFTP and IFV-PTC cases. The differences between groups in percent papillary or pseudopapillary architecture, cellularity, and tridimensionality showed a trend towards significance. Amount of colloid, dirty background, pleomorphism or atypia, nuclear pseudoinclusions, type of chromatin, and nucleolus were not significant.

CONCLUSIONS

No cytopathological feature can differentiate between invasive and encapsulated IFV-PTC. In accordance with the recently accepted category, PTC smears with cells arranged in a predominantly follicular architecture should be reported as Bethesda IV category with descriptive terms to avoid false-positive cases.