Role of Ultrasound in Predicting Tumor Invasiveness in Follicular Variant of Papillary Thyroid Carcinoma

Prognosis of invasive encapsulated follicular variant and classical papillary thyroid carcinoma: a propensity score-matched study using the SEER database

The latest World Health Organization Classification of Tumors, Fifth Edition, recognizes the invasive encapsulated follicular variant of papillary thyroid carcinoma (IEFVPTC) as a distinct malignant entity rather than a subtype of papillary thyroid carcinoma (PTC). This reclassification highlights the need to explore potential prognostic differences between IEFVPTC and classic PTC. This study utilized the Surveillance, Epidemiology, and End Results (SEER) database to compare prognoses of patients diagnosed with IEFVPTC and classic PTC between 2004 and 2019. Propensity score matching (PSM) was employed to adjust for confounding variables and reduce selection bias. Kaplan-Meier survival curves and Cox regression models were used to evaluate overall survival (OS) between the two groups. A total of 1,530 IEFVPTC and 81,508 classic PTC patients were analyzed. Before PSM, significant differences were noted in race, T-stage, N-stage, M-stage, laterality, radiotherapy, surgical modality, tumor size, and income. Post-PSM, these differences were not statistically significant (p > 0.05). Kaplan-Meier curves and Cox regression models showed no significant differences in OS between IEFVPTC and classic PTC both before and after PSM. This PSM analysis revealed no significant differences in overall survival between patients with IEFVPTC and classic PTC, suggesting that the reclassification of IEFVPTC does not translate into distinct prognostic outcomes.

Comparison of ultrasound findings of papillary thyroid carcinoma subtypes based on the 2022 WHO classification of thyroid neoplasms

Purpose

The present study aimed to analyze and compare sonographic features of papillary thyroid carcinoma (PTC) subtypes to determine whether ultrasound (US) may aid in differentiating particular subtypes.

Methods

This retrospective study enrolled 133 patients diagnosed with 142 histopathologically proven PTCs as per the fifth edition of the World Health Organization classification of thyroid neoplasms between January 2013 and May 2023. US features based on the American College of Radiology and European Thyroid Imaging and Reporting Data Systems (TIRADS), and histopathological characteristics of nodules were assessed and compared.

Results

Histopathological analysis yielded 55 (38.7%) classic PTC, 32 (22.5%) invasive encapsulated follicular variant (IEFV) PTC, 20 (14.1%) oncocytic subtype, 14 (9.9%) non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 11 (7.8%) infiltrative follicular subtype, 7 (4.9%) tall cell subtype, 2 (1.4%) solid subtype, and 1 (0.7%) diffuse sclerosing subtype. The US findings indicating malignancy, such as taller-than-wide shape, irregular margins, echogenic foci, and higher TIRADS categories, were more frequently demonstrated in nodules with classic PTC and the tall cell subtype, in line with their histopathological features. Conversely, IEFV-PTC and NIFTP rarely exhibited these high-risk sonographic features. US appearance of the oncocytic subtype more frequently overlapped with IEFV-PTC, yet hypo/very hypoechoic nodules with larger nodular diameters and higher TIRADS scores may favor the diagnosis of this subtype.

Conclusion

US features of certain subtypes may guide the differential diagnosis regarding shape, margin, echogenic foci, and TIRADS category of nodules; however, definitive subtyping is not yet possible using US images alone.

Macrofollicular Architecture in Invasive Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A Pitfall in Thyroid Practice

BACKGROUND

Predominantly macrofollicular architecture in invasive encapsulated follicular variant of papillary thyroid carcinoma (IEFVPTC-MF) is rare and often a cause of misinterpretation during pre-operative work-up and histopathology evaluation. We comprehensively evaluated the radiological, cytological, gross, microscopic, molecular and follow-up characteristics of four such cases, intending to increase its recognition and add our experience to the limited literature available.

METHODS

All such histopathologically-proven cases of IEFVPTC-MF were retrieved from the departmental archives. The clinical details, thyroid ultrasound, cytology and thyroid scan findings were reviewed. Allele-specific PCR for BRAF p.V600E, KRAS, NRAS, and HRAS mutations, and FISH assays for ETV6::NTRK3 fusion and RET fusions were performed.

RESULTS

There were four cases of IEFVPTC-MF diagnosed between 2021 and 2022, involving two males and two females. The median age at presentation was 27 years, and the duration of the disease was 1-10 years. Thyroid ultrasound was TR1 (benign; n = 1), TR2 (not suspicious; n = 2), or TR4 (moderately suspicious; n = 1). Cytology was categorized as nondiagnostic (n = 1), benign (n = 1), and atypia of undetermined significance (n = 1). The three nodules with available cytology smears showed abundant colloid. Cells were arranged as sheets/microfollicles/clusters. Nuclei were predominantly round with minimal/focal elongation, membrane irregularity, and cellular crowding. On gross examination, cut surfaces of the tumors showed variable amounts of colloid. The tumors were solid-cystic. Histopathology revealed partially encapsulated multinodular tumors. There were prominent pseudopapillae projecting into the lumina of macrofollicles. Nuclei were predominantly round with variable nuclear atypia, including chromatin clearing and multifocal presence of nuclear grooves. Pseudoinclusions were identified in two. Molecular analysis revealed NRAS codon 61 mutation and ETV6::NTRK3 fusion in one case each. Two patients had cervical lymph node and hematogenous metastases. Post-radio-active iodine, the response was structurally incomplete (n = 2), indeterminate (n = 1) and excellent (n = 1).

CONCLUSIONS

Macrofollicular architecture in invasive encapsulated follicular variant of papillary thyroid carcinoma is a major pitfall in thyroid oncology practice. Long-standing disease, and ultrasonographic and cytological features that overlap with benign disease, often lead to underdiagnosis during pre-operative evaluation. As patients may consequently develop distant metastases and have inadequate treatment response, there is a need for more vigilant understanding of the spectrum of macrofollicular thyroid disease for accurate diagnosis. ETV6::NTRK3 or other fusions, when found, present opportunities for targeted therapy.

AI diagnosis of Bethesda category IV thyroid nodules

Thyroid nodules are a common disease, and fine needle aspiration cytology (FNAC) is the primary method to assess their malignancy. For the diagnosis of follicular thyroid nodules, however, FNAC has limitations. FNAC can classify them only as Bethesda IV nodules, leaving their exact malignant status and pathological type undetermined. This imprecise diagnosis creates difficulties in selecting the follow-up treatment. In this retrospective study, we collected ultrasound (US) image data of Bethesda IV thyroid nodules from 2006 to 2022 from five hospitals. Then, US image-based artificial intelligence (AI) models were trained to identify the specific category of Bethesda IV thyroid nodules. We tested the models using two independent datasets, and the best AI model achieved an area under the curve (AUC) between 0.90 and 0.95, demonstrating its potential value for clinical application. Our research findings indicate that AI could change the diagnosis and management process of Bethesda IV thyroid nodules.

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.

[Clinical Application of the 2021 Korean Thyroid Imaging Reporting and Data System (K-TIRADS)]

In patients with thyroid nodules, ultrasonography (US) has been established as a primary diagnostic imaging method and is essential for treatment decision. The Korean Thyroid Imaging Reporting and Data System (K-TIRADS) is a pattern-based, US malignancy risk stratification system that can easily diagnose nodules during real-time ultrasound examinations. The 2021 K-TIRADS clarified the US criteria for nodule classification and revised the size thresholds for nodule biopsy, thereby reducing unnecessary biopsies for benign nodules while maintaining the appropriate sensitivity to detect malignant tumors in patients without feature of high risk thyroid cancer. Thyroid radiology practice has an important clinical role in the diagnosis and non-surgical treatment of patients with thyroid nodules, and should be performed according to standard practice guidelines for proper and effective clinical care.

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.

Clinicoradiological Characteristics in the Differential Diagnosis of Follicular-Patterned Lesions of the Thyroid: A Multicenter Cohort Study

OBJECTIVE

Preoperative differential diagnosis of follicular-patterned lesions is challenging. This multicenter cohort study investigated the clinicoradiological characteristics relevant to the differential diagnosis of such lesions.

MATERIALS AND METHODS

From June to September 2015, 4787 thyroid nodules (≥ 1.0 cm) with a final diagnosis of benign follicular nodule (BN, n = 4461), follicular adenoma (FA, n = 136), follicular carcinoma (FC, n = 62), or follicular variant of papillary thyroid carcinoma (FVPTC, n = 128) collected from 26 institutions were analyzed. The clinicoradiological characteristics of the lesions were compared among the different histological types using multivariable logistic regression analyses. The relative importance of the characteristics that distinguished histological types was determined using a random forest algorithm.

RESULTS

Compared to BN (as the control group), the distinguishing features of follicular-patterned neoplasms (FA, FC, and FVPTC) were patient's age (odds ratio [OR], 0.969 per 1-year increase), lesion diameter (OR, 1.054 per 1-mm increase), presence of solid composition (OR, 2.255), presence of hypoechogenicity (OR, 2.181), and presence of halo (OR, 1.761) (all p < 0.05). Compared to FA (as the control), FC differed with respect to lesion diameter (OR, 1.040 per 1-mm increase) and rim calcifications (OR, 17.054), while FVPTC differed with respect to patient age (OR, 0.966 per 1-year increase), lesion diameter (OR, 0.975 per 1-mm increase), macrocalcifications (OR, 3.647), and non-smooth margins (OR, 2.538) (all p < 0.05). The five important features for the differential diagnosis of follicular-patterned neoplasms (FA, FC, and FVPTC) from BN are maximal lesion diameter, composition, echogenicity, orientation, and patient's age. The most important features distinguishing FC and FVPTC from FA are rim calcifications and macrocalcifications, respectively.

CONCLUSION

Although follicular-patterned lesions have overlapping clinical and radiological features, the distinguishing features identified in our large clinical cohort may provide valuable information for preoperative distinction between them and decision-making regarding their management.

Core needle biopsy and ultrasonography are superior to fine needle aspiration in the management of follicular variant papillary thyroid carcinomas

PURPOSE

Follicular variant papillary thyroid carcinoma (FVPTC) is a problematic entity. FVPTCs are often misdiagnosed by the standard fine needle aspiration (FNA); in addition, FVPTCs represent a mixed group of tumors with two biologically distinct subtypes: The indolent encapsulated FVPTC and the aggressive infiltrative FVPTC. Recent changes in guidelines suggests that FVPTC management may be improved if subtypes can be determined preoperatively. Preoperative assays, FNA, core needle biopsy (CNB), and ultrasonography (US) were compared for their ability to identify and subtype FVPTCs to determine the most appropriate test to manage FVPTCs.

METHODS

The preoperative assays and clinicopathologic variables of 255 resected FVPTCs cases at Samsung Medical Center between 2012 and 2016 were retrospectively evaluated.

RESULTS

CNB had the overall best ability to manage FVPTCs with the highest rate of diagnosis indicating surgery, lowest rate of inconclusive results, high sensitivity (88.9%), specificity (87.7%), negative predictive value (97.0%), diagnostic odds ratio (DOR; 56.9), and excellent predictive ability (AUC 0.906) for differentiating FVPTC subtypes. US had a moderate DOR (12.8), good predictive ability (AUC 0.802), high sensitivity (75.0%) and specificity (81.0%). CNB and US both had significantly higher accuracy for discriminating FVPTC subtypes than FNA (AUC 0.908 and 0.877 > 0.671; p < 0.05). The excellent performance of CNB could be attributed to distinct histologic differences between FVPTC subtypes.

CONCLUSION

CNB and US had superior performance to FNA in the identification and subtyping of FVPTC. In institutions with skilled and experienced operators, CNB is the preferred method for evaluating possible FVPTC lesions.

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.

2021 Korean Thyroid Imaging Reporting and Data System and Imaging-Based Management of Thyroid Nodules: Korean Society of Thyroid Radiology Consensus Statement and Recommendations

Incidental thyroid nodules are commonly detected on ultrasonography (US). This has contributed to the rapidly rising incidence of low-risk papillary thyroid carcinoma over the last 20 years. The appropriate diagnosis and management of these patients is based on the risk factors related to the patients as well as the thyroid nodules. The Korean Society of Thyroid Radiology (KSThR) published consensus recommendations for US-based management of thyroid nodules in 2011 and revised them in 2016. These guidelines have been used as the standard guidelines in Korea. However, recent advances in the diagnosis and management of thyroid nodules have necessitated the revision of the original recommendations. The task force of the KSThR has revised the Korean Thyroid Imaging Reporting and Data System and recommendations for US lexicon, biopsy criteria, US criteria of extrathyroidal extension, optimal thyroid computed tomography protocol, and US follow-up of thyroid nodules before and after biopsy. The biopsy criteria were revised to reduce unnecessary biopsies for benign nodules while maintaining an appropriate sensitivity for the detection of malignant tumors in small (1-2 cm) thyroid nodules. The goal of these recommendations is to provide the optimal scientific evidence and expert opinion consensus regarding US-based diagnosis and management of thyroid nodules.

Korean Thyroid Imaging Reporting and Data System: Current Status, Challenges, and Future Perspectives

The Korean Thyroid Imaging Reporting and Data System (K-TIRADS) is an ultrasound-based risk stratification system for thyroid nodules that has been widely applied for the diagnosis and management of thyroid nodules since 2016. This review article provides an overview of the use of the K-TIRADS compared with other risk stratification systems. Moreover, this review describes the challenges in the clinical application of the K-TIRADS, as well as future development directions toward the personalized management of patients with thyroid nodules.

Diagnostic performance of core needle biopsy as a first-line diagnostic tool for thyroid nodules according to ultrasound patterns: Comparison with fine needle aspiration using propensity score matching analysis

OBJECTIVE

This study aimed to compare the diagnostic performance of core-needle biopsy (CNB) to fine-needle aspiration (FNA) as a first-line diagnostic tool in initially detected thyroid nodules, according to ultrasound (US) patterns.

MATERIALS AND METHODS

This study included 778 consecutive nodules from 705 patients who underwent CNB from one institution and 627 nodules from 583 patients who underwent FNA from two institutions. Adjustments for significant differences in patients' characteristics were facilitated via propensity score matching. We compared the diagnostic performance of CNB and FNA for thyroid malignancy according to three diagnostic criteria for all nodules and the US patterns.

RESULTS

A 1:1 matching of 469 patients yielded no significant differences between CNB and FNA for any covariates. CNB showed a significantly higher sensitivity for malignancy than FNA with any criterion (criterion 1: category VI, criterion 2: category V and VI, criterion 3: category IV, V and VI) in overall and high suspicion nodules (90.1-99.5% vs 69.7%-88.3%, all P-values < 0.001) and low/intermediate suspicion nodules, except criterion 1 (61.9%-100% vs 36.4%-45.5%, all P ≤ .016). In ROC curve analysis, the areas under the ROC curve of CNB were significantly higher than those for FNA with any criterion in overall and high suspicion nodules (P < .001) and in low/intermediate suspicion nodules, except criterion 1 (P ≤ .008). CNB had a slightly higher minor complication rate than FNA (0.7% vs 0%, P ≥ .069).

CONCLUSION

Our study suggests that CNB has a complementary role as an alternative first-line diagnostic tool to FNA for the initial diagnosis of thyroid nodules when performed by an experienced operator.

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.

Can the American Thyroid Association, K-Tirads, and Acr-Tirads Ultrasound Classification Systems Be Used to Predict Malignancy in Bethesda Category IV Nodules?

OBJECTIVE

Management of thyroid nodules with Bethesda category III and IV cytology on fine needle aspiration (FNA) is challenging as they cannot be adequately classified as benign or malignant. Ultrasound (US) patterns have demonstrated the utility in evaluating the risk of malignancy (ROM) of Bethesda category III nodules. This study aims to evaluate the value of 3 well-established US grading systems (American Thyroid Association [ATA], Korean Thyroid Imaging Reporting and Data System [Korean-TIRADS], and The American College of Radiology Thyroid Imaging Reporting and Data System [ACR-TIRADS]) in determining ROM in Bethesda category IV nodules.

METHODS

Ninety-two patients with 92 surgically resected thyroid nodules who had Bethesda category IV cytology on FNA were identified. Nodule images were retrospectively graded using the 3 systems in a blinded manner. Associations between US risk category and malignant pathology for each system were analyzed.

RESULTS

Of the 92 nodules, 56 (61%) were benign and 36 (39%) were malignant. Forty-seven per cent of ATA high risk nodules, 53% of K-TIRADS category 5 nodules, and 50% of ACR-TIRADS category 5 nodules were malignant. The ATA high-risk category had 25% sensitivity, 82% specificity, 47% positive predictive value (PPV) for malignancy. K-TIRADS category 5 had 25% sensitivity, 85% specificity, 53% PPV for malignancy. ACR-TIRADS category 5 had 25% sensitivity, 84% specificity, 50% PPV for malignancy. None of the 3 grading systems yielded a statistically significant correlation between US risk category and the ROM (P = .30, .72, .28).

CONCLUSION

The ATA, Korean-TIRADS, and ACR-TIRADS classification systems are not helpful in stratifying ROM in patients with Bethesda category IV nodules. Clinicians should be cautious of using ultra-sound alone when deciding between therapeutic options for patients with Bethesda category IV thyroid nodules.

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.

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.

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 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.

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.

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.

European Perspective on 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: Proceedings of an Interactive International Symposium

BACKGROUND

The American Thyroid Association (ATA) management guidelines for patients with thyroid nodules and differentiated thyroid cancer (DTC) are highly influential practice recommendations. The latest revision appeared in 2015 ("ATA 2015"). These guidelines were developed predominantly by North American experts. European experts frequently have different perspectives, given epidemiological, technological/methodological, practice organization, and medicolegal differences between the respective regions.

SUMMARY

Divergent viewpoints were the focus of an invited symposium organized by the European Association of Nuclear Medicine involving 17 European thyroidologists, four ATA Guidelines Taskforce members, and an audience of 200 international experts. The group discussed the preoperative assessment of thyroid nodules, surgery and the role of pathology, radioiodine (RAI) therapy (RAIT), the assessment of initial therapy and dynamic risk stratification, and the treatment of persistent disease, recurrences, and advanced thyroid cancer. The dialogue resulted in this position paper contrasting European and ATA 2015 perspectives on key issues. One difference pertains to the permissiveness of ATA 2015 regarding lobectomy for primary tumors ≤4 cm. European panelists cited preclusion of RAIT, potential need for completion thyroidectomy, frequent inability to avoid chronic thyroid hormone replacement, and limitations of supportive evidence as arguments against widely applying lobectomy. Significant divergence involved ATA 2015's guidance regarding RAIT. European panelists favored wider use of postoperative RAIT than does ATA 2015. Rationales included the modality's association with favorable patient outcomes and generally limited toxicity, and lack of high-quality evidence supporting withholding RAIT. Additionally, European panelists favored recombinant human thyrotropin (rhTSH) in more settings than does ATA 2015, citing avoidance of hypothyroid morbidity and quality-of-life impairment, without apparent sacrifice in oncologic outcomes. Based on clinical evidence plus theoretical advantages, European experts advocated dosimetric versus fixed-activity RAIT approaches for advanced DTC. European panelists noted that the ATA 2015 risk-stratification system requires information sometimes unavailable in everyday practice. ATA 2015 recommendations regarding RAI-refractory DTC should consider potential palliative benefits of RAIT in patients who also have RAI-susceptible lesions.

CONCLUSIONS

European panelists suggested modifications to approximately one-third of ATA 2015 recommendations. Varying European and ATA 2015 perspectives can stimulate analysis and discussion of the literature and performance of primary research to resolve discrepant recommendations and potentially improve patient outcomes.

Characteristics of Follicular Variant Papillary Thyroid Carcinoma in a Pediatric Cohort

CONTEXT

In adults, noninvasive follicular variant of papillary thyroid carcinoma (FVPTC) is considered a low risk for metastasis and persistent/recurrent disease.

OBJECTIVE

The goal of this study was to assess the clinical, sonographic, and histopathologic features of FVPTC in a pediatric cohort.

DESIGN

A retrospective review of subjects <19 years of age with papillary thyroid carcinoma (PTC) who underwent thyroidectomy between January 2010 and July 2015.

SETTING

Multidisciplinary academic referral center.

PATIENTS

Patients with FVPTC, defined as a tumor ≥1 cm in the largest dimension with predominant follicular growth, complete lack of well-formed papillae, and nuclear features of PTC.

MAIN OUTCOME MEASURES

Tumor size and location, presence of a tumor capsule, capsule and vascular invasion, lymph node invasion, and distant metastasis.

RESULTS

Eighteen patients with FVPTC were identified from a case cohort of 110 patients with PTC. On histopathology, 13 (72%) had unifocal nodules and 14 (78%) had completely encapsulated FVPTC. Capsule invasion was frequent (nine of 14; 64%), and vascular invasion was found in one-third of patients (six of 18; 33%). No lymph node metastases were found in the 13 patients (72%) who had a central neck lymph node dissection. One patient with vascular invasion had distant metastases.

CONCLUSION

When strictly defined, FVPTC in pediatric patients has a low risk for bilateral disease and metastasis. Prospective studies are needed to confirm whether lobectomy with surveillance is sufficient to achieve remission in pediatric patients with low-risk FVPTC.

Prevention of total thyroidectomy in noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) based on combined interpretation of ultrasonographic and cytopathologic results

OBJECTIVE

To explore the potential preoperative ultrasonography (US) and cytopathological features to avoid total thyroidectomy in NIFTP.

CONTEXT

Recently, it has been proposed that that noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) be classified as tumours, rather than cancer.

PATIENTS

A total of 142 surgically proven follicular variant papillary thyroid carcinomas (FVPTCs; 45 NIFTP, 97 non-NIFTP; mean size: 20.4±11.0 mm, range: 10.0-65.0 mm) from 142 patients were included in this study.

MEASUREMENTS

Three preoperative features of thyroid nodules (each US finding, US and Bethesda category) were compared in NIFTP and non-NIFTP groups. The preoperative decision-making process to avoid total thyroidectomy in NIFTP was evaluated based on combination of those features.

RESULTS

In each US finding, there was only significantly less macrocalcification in the NIFTP group than in the non-NIFTP group (8.8% [4/45] vs 32.0% [31/97], P = .006). In US category, all of the NIFTP nodules were a low or intermediate suspicion (100% [45/45]). In Bethesda category, 26.7% [12/45] of the NIFTP was diagnosed as either suspicious malignancy or malignant, which increased the risk of a total thyroidectomy. In our study, a total thyroidectomy might be avoided in all of the NIFTP cases if lobectomy was selected for the nodules classified as a low or intermediate suspicion in US, despite being classified as a suspicious malignancy or malignant by cytopathology.

CONCLUSIONS

Combining the US and cytopathological results could sensitively reduce total thyroidectomy in cases of NIFTP.

An update on noninvasive follicular thyroid neoplasm with papillary-like nuclear features

PURPOSE OF REVIEW

Noninvasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) has been established in the literature as a clinically indolent tumor. Despite this, it was traditionally treated like all other PTCs. In an attempt to reduce overtreatment of this entity, a panel of experts reclassified this entity as noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP). This reclassification has led to a flurry of literature elucidating the molecular, cytologic and clinical parameters of this 'new' entity and the implications for patient management. The purpose of this review is to examine the latest literature on this tumor and explore how its emergence has impacted our current understanding of the diagnosis, management and outcomes in this entity.

RECENT FINDINGS

NIFTP is a low grade tumor with an indolent clinical course. Recent studies have begun to document the variable incidence of NIFTP, the ultrasound and cytologic findings, and the impact of the NIFTP terminology on established rates of malignancy in fine-needle aspiration and clinical outcome studies.

SUMMARY

The recent literature on molecular, radiographic and cytologic characteristics of NIFTP are building our understanding of this neoplasm and support its indolent nature.