Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features and Updates in Bethesda System for Thyroid Fine-Needle Aspiration Cytology: An Overview

[摘要] Thyroid cancer incidence rising in the community has been a matter of concern. The possibility of a certain category of papillary carcinoma, namely the encapsulated follicular variant contributing to this rise needed a thorough look in. Scientific evidence has led to this category to be taken out from the malignant categorization even though the entity has the presence of the typical papillary nuclei. A new well-defined indolent category of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has been defined with both inclusion and exclusion criteria. This has led to some disruption in the risk of malignancy assessments in the Bethesda system of thyroid fine-needle aspiration cytology. Importantly, cytology is limited in distinguishing the invasive from encapsulated follicular variants of papillary thyroid carcinomas. The new Bethesda system provides for a descriptive footnote in the category 4–6 on the need to consider the indolent counterpart NIFTP. Furthermore, category 3, atypia of undetermined significance (AUS)/follicular lesion of undetermined significance is well defined with an explanation for the reason behind using this terminology as this is a heterogeneous category. The NIFTP group is associated with RAS mutations unlike the BRAF mutations in the classical papillary carcinomas.

[学科分类] 皮肤病学

[关键词] Follicular thyroid neoplasms;neoplasm with papillary-like nuclear features;pathology;thyroid cancer;thyroidectomy