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

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

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

Analysis of a pre-2017 follicular variant papillary thyroid carcinoma cohort reclassified as noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP): an 11-year retrospective single institution experience

INTRODUCTION

Noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP), represents a distinct class of thyroid neoplasms with very low risk of adverse outcome and a set of strict histologic criteria. Introduction of NIFTP as a non-cancer has had an appreciable decrease in risk of malignancy and body of literature on this entity continues to grow. In this study, we reviewed clinical, fine-needle aspiration cytology (FNAC), imaging, and molecular findings of histologically proven NIFTPs at our institution.

MATERIALS AND METHODS

Thyroid resections during an 11-year period, with histologic diagnosis of follicular variant of papillary thyroid carcinoma (FVPTC), were retrospectively reviewed to identify NIFTP. Ultrasonographic appearance, FNA findings, and molecular findings were also reviewed.

RESULTS

Of 244 cases of FVPTC identified, 74 (30%) cases were reclassified as NIFTP. Mean tumor size was 2.5 cm. Of 33 patients with lymph node dissection, none had lymph node metastases. On imaging, 36 NIFTP (49%) showed vascularity, 25 (33%) were isoechoic to hypoechoic, there were calcifications in 14 cases (19%), and 7 cases (9%) showed a hypoechoic rim. Bethesda III/IV was the most common interpretation rendered on FNAC (31%). Seven cases had NRAS mutations and 1 case had BRAF V600E mutation. The remaining cases were either negative for BRAF V600E or had no identifiable molecular alterations.

CONCLUSIONS

A significant percentage of tumors previously diagnosed as FVPTC were reclassified as NIFTP. This tumor cannot be reliably diagnosed preoperatively on FNAC, shows no characteristic features on ultrasound and has low suspicion of malignancy. BRAF V600E mutations are infrequent in NIFTP.

SFE-AFCE-SFMN 2022 Consensus on the management of thyroid nodules : Follow-up: How and how long?

The SFE-AFCE-SFMN 2022 consensus deals with the management of thyroid nodules, a condition that is a frequent reason for consultation in endocrinology. In more than 90% of cases, patients are euthyroid, with benign non-progressive nodules that do not warrant specific treatment. The clinician's objective is to detect malignant thyroid nodules at risk of recurrence and death, toxic nodules responsible for hyperthyroidism or compressive nodules warranting treatment. The diagnosis and treatment of thyroid nodules requires close collaboration between endocrinologists, nuclear medicine physicians, surgeons, and other specialists. Therefore, this consensus statement was established jointly by 3 societies: the French Society of Endocrinology (SFE), French Association of Endocrine Surgery (AFCE) and French Society of Nuclear Medicine (SFMN); the various working groups included experts from other specialties (pathologists, radiologists, pediatricians, biologists, etc.). This section deals with the follow-up of thyroid nodules, low-grade tumors and microcarcinomas.

Variation in the Diagnosis of Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features

CONTEXT

Noninvasive encapsulated follicular variant of papillary thyroid cancer was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in January 2017. The impact of this nomenclature change at a population level remains unknown.

OBJECTIVE

Examine use of NIFTP across different US regions and populations.

DESIGN

Descriptive epidemiology study using SEER-22 data (2000-2019).

PARTICIPANTS

Individuals diagnosed with papillary or follicular thyroid cancer (2000-2019) or NIFTP (2017-2019).

MAIN OUTCOME MEASURES

Annual incidence rates of thyroid cancer by subtype and NIFTP. Using 2018-2019 data, (1) rates of NIFTP at the 17 SEER-22 sites and (2) comparison of demographics for patients diagnosed with NIFTP vs papillary and follicular thyroid cancer.

RESULTS

NIFTP comprised 2.2% and 2.6% of cases in 2018 and 2019, respectively. Between 2018 and 2019, large heterogeneity was observed in the regional use of NIFTP diagnosis, with site-specific incidence rates between 0.0% and 6.2% (median 2.8%, interquartile range 1.3-3.6%). A diagnosis of NIFTP (vs papillary and follicular thyroid cancer) in 2018 and 2019 was significantly associated with older age (P = 0.012 and P = 0.009, respectively), Black race (both Ps < 0.001), and non-Hispanic ethnicity (both Ps < 0.001).

CONCLUSIONS

Marked variation exists in the use of the NIFTP diagnosis. The recent 2021 coding change that resulted in NIFTP, a tumor with uncertain malignant potential and for which there is no long-term outcome data available, no longer being a reportable diagnosis to SEER will disproportionately affect vulnerable patient groups such as older patients and Black patients, in addition to patients who reside in regions with higher rates of NIFTP diagnoses.

Rethinking Low-Risk Papillary Thyroid Cancers < 1cm (Papillary Microcarcinomas): An Evidence Review for Recalibrating Diagnostic Thresholds and/or Alternative Labels

Background: Recalibrating diagnostic thresholds or using alternative labels may mitigate overdiagnosis and overtreatment of papillary microcarcinoma (mPTC). We aimed at identifying and collating relevant epidemiological evidence on mPTC, to assess the case for recalibration and/or new labels. Methods: We searched EMBASE and PubMed databases from inception to December 2020 for natural history, autopsy, diagnostic drift, and diagnostic reproducibility studies. Where a relevant systematic review was pre-identified, only new articles were additionally included. Non-English articles were excluded. One author screened titles and abstracts. Two authors screened full text articles, performed quality assessments, and extracted data. We undertook narrative synthesis of included evidence (pooled estimates from systematic reviews and single estimates from primary studies). Results: One systematic review of patients undergoing active surveillance found that after 5 years of follow-up, 5.3% (95% confidence interval [CI 4.4-6.4%]) of the mPTC lesions had increased in size by ≥3 mm, and 1.6% [CI 1.1-2.4%] of patients had lymph node metastases. Among 7 new primary studies (including 3 updates on 2 studies included in the systematic review), 1-5% of patients undergoing active surveillance had lymph node metastases after a median follow-up of 1-10 years. One systematic review found that subclinical thyroid cancer incidentally discovered at autopsy is relatively common, with a pooled prevalence of 11.2% [CI 6.7-16.1%] among studies that examined the whole thyroid. Four diagnostic drift studies evaluated the new classification of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). Three studies of cases previously diagnosed as papillary thyroid cancer found 1.3-2.3% were reclassified as NIFTP (reclassifications were from follicular variation of papillary thyroid cancer [FVPTC]). One study of 48 cases previously diagnosed as mPTC found that 23.5% were reclassified as NIFTP. Thirteen reproducibility studies of papillary thyroid lesions found substantial variation in the histopathological diagnosis of thyroid lesions, including FVPTC and NIFTP classifications (no study evaluated mPTC). Conclusions: This review supports consideration of recalibrating diagnostic thresholds and/or alternative labels for low-risk mPTC.

The Incidence of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Meta-Analysis Assessing Worldwide Impact of the Reclassification

Background: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification has significantly influenced the field of thyroidology. However, the extent of this impact depends upon the incidence of NIFTP in a given population. In this meta-analysis, we aimed to obtain robust information about the actual incidence of NIFTP worldwide by reviewing the published data. Methods: Comprehensive literature search was performed using electronic databases of PubMed and Web of Science over a five-year period (January 1, 2016, to January 30, 2021). The incidence of NIFTP was calculated by dividing the number of NIFTPs by the number of papillary thyroid carcinomas (PTCs). Meta-analysis of proportion and their 95% confidence interval [CI] were pooled using the random-effect model. Heterogeneity across the included studies was assessed using I² statistics. Egger's regression test and funnel plot of estimates were used to evaluate the publication bias. p-Value <0.05 was considered significant. Results: From 505 publications, we included 50 studies, all retrospective, with 100,780 PTCs and 3990 NIFTP from 92 institutions worldwide. The overall incidence of NIFTP was 6.0% [CI 4.4-8.2] among PTCs or thyroid malignancies with a high level of heterogeneity among the included studies (I² = 98.6%). NIFTP incidence was largely similar in North America and Europe (9.3% vs. 9.6%), with a significantly lower overall rate in Asia (2.1%). There was a significant decline in the reported incidence of NIFTP in non-Asian studies published after 2017 (p = 0.002). On applying our data on global thyroid cancer statistics, this reclassification would affect ∼30,881 patients annually, with a lower impact in Asia compared with North America and Europe. Conclusions: This comprehensive meta-analysis confirms that the worldwide NIFTP incidence is much lower than estimated initially. The NIFTP rates are significantly lower in Asian compared with North American and European countries. Apart from geography, NIFTP rates are significantly influenced by the nature of study, type of database used for sample collection, and the diagnostic criteria used. Introduction of NIFTP may potentially spare over 30,000 patients worldwide annually from clinical and psychological consequences of a thyroid cancer diagnosis.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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