High risk history is defined by the ATA as childhood irradiation, familial thyroid cancer, lymphadenopathy, immobility with swallowing, pain, cough, voice change, or substantial growth (>20% in two dimensions). As of 2015 guidelines, FDG avidity does not result in a size threshold < 10 mm at which FNA is suggested. For these other high-risk conditions FNA can considered at lower size cut-offs.
Abnormal lymph nodes: Short axis < 10 mm in zone 2 is defined as normal at our institution. ATA definition is of > 8-10 mm short axis, cystic areas, calcifications, peripheral vascularity, rounded morphology, absent fatty hilus, and abnormal hypoechogenicity.