NIFTPs may be reclassified not only from FVPTCs but also from follicular adenomas.

Few studies have focused on reclassifying follicular adenomas (FAs) as noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTPs), but none have been conducted in America or Europe. The aims of this study were to analyze the prevalence of NIFTP reclassified from follicular variant of papillary thyroid carcinomas (FVPTCs) and FAs before NIFTP was defined in the literature, the rate of NIFTP among PTC (papillary thyroid carcinomas) established in real time between 2017 and 2022, and demographic, ultrasonographic, and cytologic characteristics of NIFTPs compared with FVPTCs and FAs. This was a retrospective cohort study of tumors diagnosed as PTCs (n = 247) and FAs (n = 144) at a Brazilian hospital. Overall, 13.4% of PTCs and 7% of FAs were reclassified as NIFTPs. The rate of real-time diagnosed NIFTPs among PTC was 12.3%. The median tumor size was larger among NIFTPs (3.0 cm) than FVPTCs (1.1 cm; P < 0.01). A high-risk ultrasonographic pattern was rare in NIFTPs (5.6%). The cytologic classifications differed between FVPTCs and NIFTPs (P < 0.01), and the most frequent category among NIFTPs was 'follicular neoplasm' (52.6%). The category 'suspicious for malignancy' was frequent in FVPTCs and rare (5.3%) in NIFTPs. In conclusion, FVPTCs and FAs may be reclassified as NIFTPs. The prevalence of NIFTPs reclassified from FAs was lower in our cohort than in Asian studies. The rate of NIFTPs reclassified from PTC was similar to that of NIFTPs diagnosed in real time and was aligned with rates reported in studies from America and Europe. Preoperative features could not differentiate NIFTPs from FVPTCs or FAs.

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

PURPOSE: Non-invasive encapsulated follicular variant of papillary thyroid cancer was reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). These neoplasms have an extremely low malignant potential. The aim of this study was (1) to assess the prevalence of NIFTP in patients with papillary thyroid carcinoma, (2) to evaluate their outcomes, and (3) to determine their molecular profile. METHODS: Multicenter, descriptive, retrospective study. Patients with papillary thyroid cancer diagnosed from January 2006 to December 2016 from 11 referral centers were included. Diagnosis of NIFTP was based on criteria described by Nikiforov et al. in 2018. At least two pathologists agreed on the diagnosis. Two thousand six hundred and seventy-seven papillary thyroid cancer patients were included; 456 (17%) of them were follicular variant papillary thyroid cancer, and 30 (1.12%) fulfilled diagnostic criteria for NIFTP. RESULTS: Each of the 30 included patients underwent a total thyroidectomy, and 50% were treated with radioiodine (median dose 100 mCi). After a median follow-up of 37 months, 84% of patients had an excellent response, 3% had an indeterminate response and data was missing in the remaining 13%. No metastatic lymph nodes, distant metastases or recurrences were found. RAS mutations were detected in 4 patients (13%). CONCLUSION: The prevalence of NIFTP in our series is amongst the lowest reported. Excellent outcomes of patients underscore their low malignant potential. Molecular findings differ from other series, probably related to environmental or ethnic features of our population and the meticulous criteria for diagnosing NIFTP.

Neoplasia folicular tiroidea no invasiva con características nucleares de tipo papilar (Noninvasive follicular thyroid neoplasm with papillary-like nuclear features o NIFTP): en qué estamos hoy, a propósito de un caso / Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP): we are we today, about a case

Es bien conocido que ha existido en las últimas décadas un incremento en los casos de cáncer diferenciado de tiroides, especialmente los microcarcinomas. Diversos factores han contribuido a pesquisar pequeños cánceres como el aumento de la disponibilidad de exámenes imagenológicos. Estos pequeños cánceres tiroideos pueden tener un comportamiento no agresivo y no producir letalidad; esto es lo que se conoce como sobrediagnóstico. Esto último tiene implicancias tanto médicas como económicas por terapias agresivas. Así, desde el año 2015, un grupo de expertos cambia la nomenclatura en anatomía patológica del carcinoma papilar tiroideo variante folicular encapsulado (NIEFVPTC de sus siglas en inglés) por Neoplasia folicular tiroidea no invasiva con características nucleares de tipo papilar (NIFTP de sus siglas en inglés). Este cambio se basó en un estudio de Nikiforov donde los NIEFVPTC no tenían efectos adversos ni mortalidad en su seguimiento. Así, la intención inicial del cambio de nomenclatura es eliminar la palabra cáncer y evitar los sobretratamientos innecesarios. Presentamos un caso clínico de una paciente que se sometió a cirugía por un nódulo tiroideo clasificado Bethesda III donde la biopsia definitiva posterior a cirugía evidenció que se trataba de un NIFTP. A raíz de este caso analizamos la literatura hasta la fecha de esta nueva entidad y hacemos un repaso histórico de los carcinomas papilares tiroideos variante folicular. Además, desarrollamos nuevas interrogantes que se plantean desde este nuevo diagnóstico anatomopatológico, de cómo sospecharlo previo a una cirugía, cuál es la cirugía de elección, y cómo debiera ser el seguimiento una vez diagnosticado.

It is well known that there has been an increase in cases of differentiated thyroid cancer in recent decades, especially microcarcinomas. Several factors have contributed to diagnose small cancers such as the increased availability of imaging tests. These small thyroid cancers can have a non-aggressive behavior and not cause lethality, this is what is known as overdiagnosis. The latter has medical as well as economic implications for aggressive therapies. Thus, since 2015, a group of experts has changed the nomenclature in pathological anatomy of encapsulated variant papillary thyroid carcinoma (NIEFVPTC) for non-invasive thyroid follicular neoplasia with papillary nuclear characteristics (NIFTP). This change was based on a Nikiforov study where the NIEFVPTC had no adverse effects or mortality in their follow-up; thus, the initial intention of the nomenclature change is to eliminate the word cancer and avoid unnecessary over-treatments. We present a clinical case of a patient who underwent surgery for a thyroid nodule classified Bethesda III where the definitive biopsy after surgery showed that it was a NIFTP. Following this case, we analyze the literature to date of this new entity and make a historical review of the follicular variant papillary thyroid carcinomas. In addition, we develop new questions that arise from this new pathological diagnosis, how to suspect it prior to surgery, what is the surgery of choice, and what should the follow-up once diagnosed.

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

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

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features.

Recently, it was proposed that some papillary thyroid carcinomas (PTC) will no longer be termed 'cancer' and are christened as 'noninvasive follicular thyroid neoplasm with papillary-like nuclear features' (NIFTP). As this is a recent definition, little information is available about NIFTP. The objective of this study was to report the frequency, ultrasonographic appearance, cytology result and long-term evolution of cases of NIFTP seen at our institution. We excluded tumours ≤1 cm. The sample consisted of 129 patients. Sixty-four patients were submitted to total thyroidectomy and 65 to lobectomy. These patients with NIFTP did not receive radioiodine. NIFTP corresponded to 15% of cases diagnosed as PTC >1 cm. An ultrasonographic appearance considered to be of low suspicion for malignancy was common in NIFTP (32.5%), whereas a highly suspicious appearance was uncommon (5%). NIFTP frequently exhibited indeterminate cytology (62%), while malignant cytology was uncommon (4%). The patients were followed up for 12-146 months (median 72 months) after surgery. None of the patients developed structural disease during follow-up. Comparing the concentrations of thyroglobulin (Tg) and anti-Tg antibodies (TgAb) obtained 6-12 months after surgery and in the last assessment, none of the patients exhibited an increase in these markers.