Variants of Papillary Thyroid Carcinoma: An Algorithmic Cytomorphology-Based Approach to Cytology Specimens

Abstract

Background: Thyroid cancer accounts for 1% of cancer cases in developed countries, in which papillary thyroid carcinoma (PTC) is the most common type. There are multiple variants of PTC described to date, some of them with aggressive behavior and poor clinical outcome. These variants are well described and accepted in recent guidelines of many international societies, and the prognostic and management implications are well laid out. Due to their established clinical importance and to guide appropriate surgical management, it is now imperative in clinical practice, including cytopathology, to differentiate aggressive variants from nonaggressive ones. This review aims to describe the variants of PTC and to provide a practical algorithmic approach to facilitate the cytological diagnosis of these variants. Summary: Subtyping PTC variants on fine needle aspiration cytology (FNAC) is challenging even for the most experienced cytopathologist. To facilitate a correct subtyping on FNAC, we propose a stepwise approach that is mainly designed for conventional smear methodology. This approach requires first to stratify the lesions into oncocytic and nononcocytic features before analyzing further details in cell morphology and pattern. Key Messages: (1) Subtyping in PTC is possible on cytopathology. (2) The main aim of the cytopathologist is to differentiate aggressive from nonaggressive variants. (3) The subtyping of PTC can help in the surgical management of the patients.

Diagnostic Value of Serum lncRNA HOTAIR Combined with Galectin-3 in Benign and Papillary Thyroid Carcinoma

“…25 Although its characteristics are classically considered as an indolent clinical process with long-term survival rates, some histological variants can have aggressive behaviors and are related to poor clinical outcomes. 26 Therefore, it is of vital importance to study the mechanism and the diagnostic markers of PTC. Evidence has shown that lncRNA HOTAIR and Glactin-3 play an essential role in PTC.…”

Do Histologically Aggressive Subtypes of Papillary Thyroid Microcarcinoma have Worse Clinical Outcome than Non-Aggressive Papillary Thyroid Microcarcinoma Subtypes? A Multicenter Cohort Study

“…Therefore, the aggressive subtypes of PTC have been classified as "intermediate risk" for recurrence in the latest American Thyroid Association (ATA) guidelines, irrespective of their size [5]. Unfortunately, despite total thyroidectomy and central LN dissection have been recommended for the treatment of aggressive subtypes of PTMC, subtyping of PTC by cytopathological evaluation of the fine needle aspiration (FNA) specimens is challenging, even for the most experienced cytopathologists [6,12]. Therefore, most of the cases are diagnosed after the histopathological evaluation of surgical specimens [6,12].…”

“…Therefore, the aggressive subtypes of PTC have been classified as “intermediate risk” for recurrence in the latest American Thyroid Association (ATA) guidelines, irrespective of their size 5 . Unfortunately, despite total thyroidectomy and central LN dissection have been recommended for the treatment of aggressive subtypes of PTMC, subtyping of PTC by cytopathological evaluation of the fine needle aspiration (FNA) specimens is challenging, even for the most experienced cytopathologists 6 12 . Therefore, most of the cases are diagnosed after the histopathological evaluation of surgical specimens 6 12 .…”

Prediction of classical versus non classical papillary thyroid carcinoma subtypes from cytology of nodules classified according to TIRADS

“…US-based risk stratification systems (RSSs), often referred as Thyroid Imaging Reporting and Data Systems (TIRADSs), mainly apply to PTC, and not to other thyroid cancers [ 9 – 12 ]. Fine-needle aspiration cytology (FNAC) has been widely used as the most effective preoperative evaluation tool to detect PTC [ 13 , 14 ]. The third edition of The Bethesda system for reporting thyroid cytopathology (TBSRTC) even included a detailed definition with particular criteria for some of these PTC subtypes but did not recommend formulating the diagnosis of a specific PTC subtype by cytology [ 15 ].…”

“…The third edition of The Bethesda system for reporting thyroid cytopathology (TBSRTC) even included a detailed definition with particular criteria for some of these PTC subtypes but did not recommend formulating the diagnosis of a specific PTC subtype by cytology [ 15 ]. This is because the diagnosis of PTC subtypes by preoperative FNAC may not be easy or reliable even for a skilled cytopathologist [ 13 – 15 ]. Similarly, preoperative diagnosis of a PTC subtype using nUS is challenging, and the US characteristics and difference for various subtypes of PTC are still unclear [ 16 ].…”