For the initial assessment of a neck mass in primary care, ultrasound (US) is the recommended first-line imaging modality. Ultrasound provides detailed greyscale imaging that helps characterize the mass, particularly for thyroid nodules, and is widely endorsed as the initial diagnostic test to evaluate malignancy risk and guide further management such as fine needle aspiration cytology (FNAC) if indicated NICE NG230.
Cross-sectional imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI) are generally not routinely recommended at the initial assessment stage unless there are specific clinical indications such as suspicion of advanced disease (e.g., T3 or T4 thyroid cancer), nodal involvement, or metastases NICE NG230.
In cases where the neck mass is unexplained and persistent, especially in adults aged 45 and over, urgent referral for suspected cancer pathways is advised rather than immediate advanced imaging in primary care NICE NG12.
Positron emission tomography–computed tomography (PET-CT) is reserved for more complex cases, such as when no primary tumor is identified after initial investigations including panendoscopy, and is not part of the initial primary care assessment NICE CG104.
Therefore, in primary care, the initial imaging approach to a neck mass should focus on ultrasound to characterize the lesion and guide further referral or investigation, with CT, MRI, or PET-CT reserved for specialist assessment or staging NICE NG230,NICE NG12,NICE CG104 Pynnonen et al. 2017.