New Concept of the Encapsulated Follicular Variant of Papillary Thyroid Carcinoma and Its Impact on the Bethesda System for Reporting Thyroid Cytopathology: A Single-Institute Experience

Abstract

Background: The encapsulated follicular variant (EFV) of papillary thyroid carcinoma (PTC) is the most discussed entity in thyroid pathology. Recently, the question of whether or not EFV-PTC is a malignant entity has been the subject of renewed discussion in the light of recent molecular and clinical studies. The aim of this study was to analyze the malignancy ratios of each category of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) if EFV-PTC is no longer considered as a malignant entity. Materials and Methods: Data on thyroid fine-needle aspirations (n = 1,886) with surgical follow-up between 1999 and 2014 were studied. EFV-PTC cases constituted 27% (94/343) of the malignant cases. Results: Malignancy ratios were determined as nondiagnostic, benign, atypia/follicular lesion of undetermined significance, suspicious for follicular neoplasm/follicular neoplasm, suspicious for malignancy, and malignant categories of the TBSRTC in 13, 7, 45, 30, 72 and 98%, respectively. If EFV-PTC was not regarded as malignant, malignancy ratios would decrease to 6.5, 6, 30, 10, 48, and 87% for each category in the same order. Conclusions: The current study showed that the most significant decrease in relative malignancy ratios was seen in the suspicious for follicular neoplasm/follicular neoplasm category (66% relative decrease), but all categories represented a considerable decrease.

Noninvasive follicular neoplasm with papillary like nuclear features: A comprehensive analysis with a diagnostic algorithm

“…A recent meta‐analysis by Layfield et al has shown that NIFTP remarkably affect risk of malignancy in indeterminate Bethesda categories . In our study, similar to those by Faquin et al and Canberk et al, the highest reduction in risk of malignancy was in FN/SFN Bethesda category (27%) followed by non‐diagnostic category (20%). Although lesser impact is known in benign category but special attention should be given to this subset, which may require closer monitoring compared to non‐neoplastic benign nodules.…”

“…Almost 3 years have passed since the introduction of this new entity and experiences from different countries and institutions have been published in an attempt to evaluate whether certain degree of disagreement still persists or whether the new diagnostic criteria are in complete harmony with the diagnosis and management. In spite of Asian continent being a major contributor to worldwide prevalence of thyroid cancer (according to GLOBOCON database; estimated 48% new cases in 2012), the prevalence of NIFTP in Asians has not been reported extensively as compared with the western world . There are limited studies from Asia and even fewer form India and those present have reported a significantly lower prevalence (0%‐5%) as compared to western data (15%‐25%) …”

“…The extent of all the changes related to the NIFTP reclassification apparently depends on the incidence of NIFTP in a certain population. Approximately, 30 studies have been conducted in America, Europe and Asia reporting variable incidence . Bychkov et al, in a meta‐analysis, documented an average worldwide prevalence rate of 9.1%, with a lower rate in Asian studies (1.6%) as compared with non‐Asian countries (13.3%) .…”

Impact of the Reclassification of the Non-Invasive Follicular Variant of Papillary Carcinoma as Benign on the Malignancy Risk of the Bethesda System for Reporting Thyroid Cytopathology: A Meta-Analysis Study

“…We also performed our own study of malignancy rates before and after the reclassification of some follicular variant papillary carcinomas of the thyroid to the benign NIFTP designation. The studies of Faquin et al [10] , Strickland et al [11] , Canberk et al [12] and our own study examined a total of 9,796 FNAs of thyroid nodules. The results of this meta-analysis showed that the malignancy rates obtained using the new system (utilizing NIFTP) were significantly lower in 4 diagnostic categories ( Table 1 ).…”

“…We performed an extensive search of the published literature for studies addressing the impact on the malignancy rate of the original TBSRTC categories if some follicular variants of papillary thyroid carcinoma were reclassified as NIFTP (a benign lesion). Our literature review found only 3 studies addressing this issue [10][11][12] . We also performed our own study of malignancy rates before and after the reclassification of some follicular variant papillary carcinomas of the thyroid to the benign NIFTP designation.…”