Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: An Evidence-Based Nomenclature Change

THADA-IGF2BP3 gene fusions in thyroid fine needle aspiration is involved in the pathway to "noninvasive follicular thyroid neoplasm with papillary-like nuclear features"

BACKGROUND

The increased usage and adaptation of molecular testing of thyroid fine needle aspirations (FNA) has expanded the variety and number of gene fusions identified. While the identified number of molecular alterations is increasing, the definitive association between preoperative molecular analysis and phenotype has yet to be established. The aim of this study was to examine Thyroid adenoma-associated (THADA)-IGF2BP3 molecular fusions with FNA categorization, surgical pathology diagnosis, and other molecular alterations detected by ThyroSeq Genomic Classifier testing.

METHODS

FNA cytology samples of thyroid nodules from 04/2017 to 01/2023 with the diagnosis of atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS; Bethesda III) or follicular neoplasm suspicious for follicular neoplasm (FN/SFN; Bethesda IV) with associated ThyroSeqV3 testing were reviewed. Parameters including patient demographics, FNA diagnosis, ThyroSeq V3 results, and surgical pathology follow up were examined.

RESULTS

87 out of 249 (35%) FNA specimens of thyroid nodules displayed molecular alterations. 64 cases (74%) had a cytology diagnosis of AUS and 23 (26%) had FN. RAS mutation was observed in 48 cases. On surgical follow-up, 17 (35%) cases showed non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), while 14 (29%) patients had a malignant diagnosis. THADA-IGF2BP3 fusions were seen in 8 cases, all with NIFTP on surgical pathology follow-up (100%).

CONCLUSIONS

Analysis of THADA-IGF2BP3 fusion, in our institutional series, shows close association with NIFTP cases. THADA-IGF2BP3 fusion, which seems to be a favorable prognostic indicator in general, may serve as a molecular marker for non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).

Pathology diagnosis of intraoperative frozen thyroid lesions assisted by deep learning

BACKGROUND

Thyroid cancer is a common thyroid malignancy. The majority of thyroid lesion needs intraoperative frozen pathology diagnosis, which provides important information for precision operation. As digital whole slide images (WSIs) develop, deep learning methods for histopathological classification of the thyroid gland (paraffin sections) have achieved outstanding results. Our current study is to clarify whether deep learning assists pathology diagnosis for intraoperative frozen thyroid lesions or not.

METHODS

We propose an artificial intelligence-assisted diagnostic system for frozen thyroid lesions that applies prior knowledge in tandem with a dichotomous judgment of whether the lesion is cancerous or not and a quadratic judgment of the type of cancerous lesion to categorize the frozen thyroid lesions into five categories: papillary thyroid carcinoma, medullary thyroid carcinoma, anaplastic thyroid carcinoma, follicular thyroid tumor, and non-cancerous lesion. We obtained 4409 frozen digital pathology sections (WSI) of thyroid from the First Affiliated Hospital of Sun Yat-sen University (SYSUFH) to train and test the model, and the performance was validated by a six-fold cross validation, 101 papillary microcarcinoma sections of thyroid were used to validate the system's sensitivity, and 1388 WSIs of thyroid were used for the evaluation of the external dataset. The deep learning models were compared in terms of several metrics such as accuracy, F1 score, recall, precision and AUC (Area Under Curve).

RESULTS

We developed the first deep learning-based frozen thyroid diagnostic classifier for histopathological WSI classification of papillary carcinoma, medullary carcinoma, follicular tumor, anaplastic carcinoma, and non-carcinoma lesion. On test slides, the system had an accuracy of 0.9459, a precision of 0.9475, and an AUC of 0.9955. In the papillary carcinoma test slides, the system was able to accurately predict even lesions as small as 2 mm in diameter. Tested with the acceleration component, the cut processing can be performed in 346.12 s and the visual inference prediction results can be obtained in 98.61 s, thus meeting the time requirements for intraoperative diagnosis. Our study employs a deep learning approach for high-precision classification of intraoperative frozen thyroid lesion distribution in the clinical setting, which has potential clinical implications for assisting pathologists and precision surgery of thyroid lesions.

Intratumoural metastasis of primary lung adenocarcinoma to non-invasive follicular thyroid neoplasm with papillary-like nuclear features

Metastasis to the thyroid gland is very uncommon with an incidence of 2-3% of all thyroid malignancies. A higher incidence is noted in autopsy studies indicating incidental detection. However, tumour-to-tumour metastasis is extremely uncommon with a handful of cases published in the literature to date. Also, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFT-P) is a rare neoplasm; diagnosis requires meticulous sampling of the entire capsule and fulfilment of other diagnostic criteria. We report a case of primary adenocarcinoma of lung in a 57-year-old female who additionally had a left thyroid nodule which appeared suspicious on ultrasonography. Histology of lung tumour was conventional papillary adenocarcinoma while aspiration cytology from the thyroid raised suspicion of metastatic adenocarcinoma. On hemithyroidectomy, the thyroid nodule showed metastatic adenocarcinoma in the centre of the nodule, while the peripheral portion showed non-invasive follicular thyroid neoplasm with papillary-like nuclear features; the diagnosis of which was confirmed with complete sampling of the thyroid capsule. The immunoprofile also supported the above dual histology. This is an extremely uncommon occurrence and metastasis within a NIFT-P has not been reported to the best of our knowledge.

The age threshold of the 8th edition AJCC classification is useful for indicating patients with aggressive papillary thyroid cancer in clinical practice

BACKGROUND

Papillary thyroid cancer (PTC) is unique among cancers in that patient age is a consideration in staging. One of the most important modifications in the 8th Edition of the American Joint Committee on Cancer (AJCC) classification is to increase the age cut off for risk stratification in PTC from 45 to 55 years. However, whether this cut off is useful in clinical practice remains controversial. In the present study, we assessed how well this new age threshold stratifies patients with aggressive PTC.

METHODS

We retrospectively analyzed the clinicopathological features and overall survival rate of patients with PTC admitted to and surgically treated at a single surgical center. The study protocol was divided into two series. In each series all patients (n = 523) were divided in 2 groups according to age cut off. In the first series (cut off 45) patients < 45 (n = 193) vs. ≥45 (n = 330) were compared, and in the second series (cut off 55) patients < 55 (n = 306) vs. ≥55 (n = 217) were compared.

RESULTS

The rate of the prevalence of locally advanced disease (pT3 and pT4) was significantly higher in the patients above 55 years old than in those below 55 years old (p = 0.013). No significant differences were found for this parameter in series with cut off point 45 years old. A significantly higher risk of locally advanced disease T3 + T4 (OR = 4.87) and presence of LNM (N1) (OR = 3.78) was observed in ≥45 years old group (p = 0.021 and p < 0.0001, respectively). More expressive results were found for the patients ≥55 years old group, where the risk of locally advanced disease (T3 + T4) was higher (OR = 5.21) and LNM presence was OR = 4.76 (p < 0.001 and p < 0.0001, respectively). None of the patients below 55 years old showed distant metastasis, but 19 patients above 55 years old showed M1 (p < 0.0001). In older patients group (≥55 years old) we observed deaths related thyroid cancer in 11 individuals.

CONCLUSIONS

The age cut off of 55 years old for risk stratification proposed by the 8th Edition of AJCC effectively stratifies PTC patients with a poor prognosis, indicating it is likely to be useful in clinical practice.

A closer look at NIFTP

Despite the rise in the incidence of papillary thyroid carcinoma (PTC) during the last 30 years, the mortality rate due to PTC has remained static. One reason for this phenomenon is the indolent nature of some of the tumors that are diagnosed as PTC. A subgroup of tumors, which often exhibited such indolent behavior, was encapsulated/well-circumscribed follicular lesions that showed PTC nuclear features. Despite their indolent behavior, these tumors were managed as was any other PTC, often with total thyroidectomy and radioactive iodine (RAI) treatment. In order to prevent overtreatment of these tumors, they were recently reclassified as "non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)." Since it is proposed that NIFTP be managed in a more conservative manner, its diagnosis is now based on strict histological criteria. The genetic basis of these diagnostic criteria and the utility of molecular markers in the diagnosis of NIFTP are currently being scrutinized. The aim of this review is to discuss the events that led to the emergence of the term NIFTP, as well as its histological and molecular background.

Molecular trait of follicular-patterned thyroid neoplasms defined by MALDI-imaging

In the field of thyroid neoplasms, the most interesting recent change regards the introduction of a new terminology for follicular-patterned thyroid tumors, named Noninvasive Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP). This pre-malignant tumor is considered to be the putative precursor of invasive carcinoma. However, given that several issues are still unresolved, the application of ancillary tools, based on omics-techniques, may improve the clinical management of these challenging cases. The present paper highlights the proteomic profiles of a series of NIFTPs submitted to Fine Needle Aspirations (FNAs) and analysed by MALDI-imaging in order to confirm the heterogeneous phenotype of nodules included in the present NIFTP terminology and to underline the necessity of more accurate biomarkers that can be used for their characterization. Ethical and economic implications in terms of healthcare costs, operative risks, morbidity, as well as the potential need for lifelong hormone replacement therapy, seem to be significant reasons to approach the characterization of NIFTPs using alternative tools such as MALDI-MSI.

Comparison of Survival and Risk Factors of Differentiated Thyroid Cancer in the Geriatric Population

Purpose: The incidence rate of differentiated thyroid cancer (DTC), the most common type of thyroid cancer, has increased in the past two decades. The present study analyzed the clinical and pathological characteristics of DTC, and discussed the risk factors for survival in elderly age-risk DTC patients.

Methods: Elderly patients who were diagnosed with DTC, and subsequently underwent surgery for DTC, were identified from the SEER database (1988–2008). Based on histology, these patients were divided into C-PTC, FV-PTC, and FTC. The clinical characteristics, pathological features, and treatments undertaken were compared among these patients. Cox proportional hazards analysis was performed to evaluate the risk factors to disease-specific survival (DSS).

Results: In elderly DTC patients, FV-PTC shows intermediate tumor features compared to C-PTC and FTC, but presented a better outcome. Being male, African-American, tumors sized bigger than 4 cm, extrathyroidal extension, lymph node metastasis, and distant metastasis, were all strong risk factors for DSS in elderly DTC patients (all p < 0.05). No difference was found between lobectomy and total thyroidectomy with respect to DSS, and radiation therapy conferred no apparent advantage with respect to DSS (both p > 0.05).

Discussion: Patients with FV-PTC needed more specific histology cataloging and risk assessment, suggesting conservative therapy. Risk stratification should be paid attention to, and treatment should be individualized for elderly patients.

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

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

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: 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.

Molecular Profiling of Follicular Variant of Papillary Thyroid Cancer Reveals Low-Risk Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Paradigm Shift to Reduce Aggressive Treatment of Indolent Tumors

INTRODUCTION

Encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) has been reclassified into noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) and invasive EFVPTC. NIFTP is considered a low-risk neoplasm. Therefore, follicular variant of papillary thyroid cancer (FVPTC) presently has two distinct histopathological subtypes - invasive EFVPTC and infiltrative/diffuse FVPTC. Molecular characteristics of these groups remain unclear.

METHODOLOGY

Thirty FVPTCs (10 NIFTPs, 12 invasive EFVPTCs, and 8 infiltrative/diffuse variants) were reviewed and screened for BRAF and RAS mutations by restriction fragment length morphism-polymerase chain reaction (PCR) and Sanger sequencing. The mRNA expression levels of iodine-metabolizing genes were analyzed using real-time PCR. The mutations status and mRNA expression levels were correlated with clinicopathological features.

RESULTS

All 10 NIFTPs had predominant follicular pattern. One case showed NRAS mutation, whereas none showed BRAF mutation. All invasive EFVPTC had capsular and/or lymphovascular invasion and 4/12 showed lymph node metastasis. BRAF and NRAS were seen in three cases each of invasive FVPTC. All eight infiltrating/diffuse FVPTCs showed infiltration into adjacent thyroid parenchyma and lymph node metastasis.

CONCLUSION

BRAF mutation was observed in 62.5% of cases; however, no NRAS mutation was found. Sodium iodide symporter (NIS) expressions in NIFTP were similar to that of normal thyroid tissue, whereas it was downregulated in invasive and infiltrative/diffuse FVPTC. Our study supports the argument that NIFTP can be considered as low-risk follicular thyroid neoplasm. Those tumors that harbor BRAF mutations may be offered a complete thyroidectomy because they show decreased expression of NIS gene which confers a tendency to lose radioactive iodine avidity and further recurrence of the tumor.