The ultrasound "U" classification of thyroid nodules has been developed by the British Thyroid Association as part of their 2014 guidelines on the management of thyroid cancer.
It allows for stratifying thyroid nodules as benign, suspicious or malignant based on ultrasound appearances termed U1-U5. This is used to streamline further investigation and management.
- no nodules
- hyperechoic or isoechoic with a halo
- cystic change with ring down artefact (colloid)
- microcystic or spongiform appearance
- peripheral egg-shell calcification
- peripheral vascularity
- solid homogenous markedly hyperechoic nodule with halo (follicular lesions)
- hypoechoic with equivocal echogenic foci or cystic change
- mixed or central vascularity
- solid hypoechoic (compared with thyroid)
- solid very hypoechoic (compared with strap muscles)
- hypoechoic with disrupted peripheral calcification
- lobulated outline
- solid hypoechoic with a lobulated or irregular outline and microcalcification
- solid hypoechoic with a lobulated or irregular outline and globular calcification
- intranodular vascularity
- taller than wide axially (AP > TR)
- characteristic associated lymphadenopathy
Treatment and prognosis
U1 and U2 nodules require do not require FNA or follow-up imaging in the absence of concerning clinical features.
U3 and above nodules require FNA with further management based on resultant cytology, radiology and clinical findings. Many units have a low threshold for performing diagnostic hemithyroidectomies for nodules that are both radiologically and cytologically suspicious.