Thyroid FNA terminology: The case for a single unified international system for thyroid FNA reporting

Abstract

The use of reporting terminologies for thyroid FNA cytology enables standardisation and international alignment of the reporting of thyroid cytology results, which is essential. There are currently three major internationally recognised systems: Bethesda (TBS), UK RCPath (Thy), and Italian (TIR). A fourth terminology system used in Japan has identical categories to TBS but with different nomenclature. The aim of this review is to discuss the strengths and weaknesses of the TBS, UK RCPath, and TIR systems, and to make the case for international terminology harmonisation and standardisation.

The Italian Consensus for the Classification and Reporting of Thyroid Cytology: Cytohistologic and molecular correlations on 37,371 nodules from a single institution

“…Regardless of the overlapping morphologic features of TIR 3B and of category IV of the Bethesda system, the corresponding ROMs differ: 25%-40% for Bethesda category IV and 47% for TIR 3B. 7 Similarly, the JTA system reported ROMs that varied from 5% to 15% for indeterminate A-1 to 40%-60% for indeterminate A-3, showing a strong similarity to the Italian system. Conversely, the UK RCPath system reported pooled ROMs of 25% for Thy3a and 27.3% for Thy3f, which were close to the ROMs observed in the Bethesda system.…”

“…This morphologic difference justifies, at least in part, the lowest ROM of TIR 3A (pooled ROM, 17%) compared with the ROM of atypia of undetermined significance/follicular lesion of undetermined significance (category III; pooled ROM, 21.5% in Western patient cohorts). 7 The follicular neoplasm/suspicious of malignancy category (category IV) of the Bethesda system encompasses thyroid aspirates that exhibit architectural atypia and mild cytologic atypia, including Hurthle cell (oncocytic) neoplasms. Similarly, in the Italian system, the high-risk indeterminate category (TIR 3B) includes both high cellularity aspirates with microfollicular/trabecular architecture and poor colloid and aspirates with some degree of nuclear atypia, insufficient to make a suspicion of PTC.…”

“…All cytologic specimens were stained with Papanicolaou, evaluated by expert thyroid cytopathologists, and classified according to the ICCRTC. 6 This thyroid FNA classification encompasses the following six diagnostic categories (Table 1) [1][2][3][4][5][6][7][8][9][10][11][12][13] :…”

“…6 The ICCRTC system is basically comparable with other internationally recognized systems-in particular, the Bethesda System for Reporting Thyroid Cytology (Bethesda) and the UK Royal College of Pathologists (UK RCPath) classification for thyroid FNA-although some differences in terminology are evident, especially in the indeterminate categories. 7,8 The expression indeterminate cytology commonly refers to the ICCRTC TIR 3A and TIR 3B classifications and the Bethesda class III or IV, which are associated with malignancy rates that vary from 10% to 40%. In the presence of an indeterminate result, the possible clinical actions include the repetition of FNA, molecular testing, and/or diagnostic lobectomy.…”

“…In our practice, thyroid FNAs are routinely diagnosed according to the Italian Consensus for the Classification and Reporting of Thyroid Cytology (ICCRTC) 6 . The ICCRTC system is basically comparable with other internationally recognized systems—in particular, the Bethesda System for Reporting Thyroid Cytology (Bethesda) and the UK Royal College of Pathologists (UK RCPath) classification for thyroid FNA—although some differences in terminology are evident, especially in the indeterminate categories 7,8 . The expression indeterminate cytology commonly refers to the ICCRTC TIR 3A and TIR 3B classifications and the Bethesda class III or IV, which are associated with malignancy rates that vary from 10% to 40%.…”