Table 2.

Size cut-offs for performing FNA recommended by each RSS.

RSS	TIRADS 2 or Very Low Risk	TIRADS 3 or Low Risk	TIRADS 4 or Intermediate Risk	TIRADS 5 or High Risk	Small Nodules < 10 mm
Chilean TIRADS	No FNA or follow-up	FNA (no cut-off) or follow-up	FNA (no cut-off)	FNA (no cut-off)	FNA if >3–4 mm and feasible
Kwak-TIRADS	No FNA	No FNA	TIRADS 4a: ≥25 mm TIRADS 4B: 15 mm	TIRADS 4 C and 5: ≥10 mm	No FNA
BTA	No FNA	All nodules	All nodules	All nodules	-
AACE	No FNA	≥20 mm and growing lesion or risk factors	≥20 mm	≥10 mm	<5 mm no FNA 5–10 mm FNA if clinical or US risk factors or PP
ATA	≥20 mm or observation	≥15 mm	≥10 mm	≥10 mm	5–10 mm FNA if clinical or US risk factors or PP
K-TIRADS	≥20 mm	≥15 mm	≥10 mm	≥10 mm	≥5 mm selective cases
EU-TIRADS	No FNA	>20 mm	>15 mm	>10 mm	FNA or active surveillance, PP
ACR-TIRADS	No FNA	≥25 mm	≥15 mm	≥10 mm	No FNA
C-TIRADS	No FNA	No FNA	≥15 mm	≥10 mm	US risk factors

Note: PP = patient’s preference.