How can I differentiate between benign and malignant thyroid conditions in a primary care setting?

In primary care, differentiating benign from malignant thyroid conditions involves a combination of clinical assessment, thyroid function tests (TFTs), and careful consideration of referral criteria rather than routine imaging or invasive tests.

Clinical features suggestive of malignancy include an unexplained thyroid lump, associated unexplained hoarseness or voice change, cervical or supraclavicular lymphadenopathy, sudden onset of a rapidly expanding painless thyroid mass, compressive symptoms such as breathlessness or dysphagia, and other red flags or risk factors for malignancy. These features warrant urgent specialist referral within 2 weeks ¹.

Initial investigations in primary care should include serum thyroid function tests (TSH, FT4, FT3 as indicated) to assess thyroid status, as abnormal TFTs can guide referral pathways. For example, a low TSH may indicate a hyperfunctioning nodule requiring radionuclide scanning, while abnormal TFTs with a non-suspicious nodule generally have a low risk of malignancy but still require routine specialist referral ¹.

Imaging and further investigations such as neck ultrasound and fine-needle aspiration cytology (FNAC) are not routinely arranged in primary care because ultrasound is highly sensitive but may delay diagnosis if not coordinated with specialist assessment. Ultrasound is primarily used by specialists to risk-stratify nodules and guide FNAC ¹,².

Monitoring in primary care may be appropriate for longstanding, stable, non-suspicious nodules without red flags or lymphadenopathy, or small (<1 cm), asymptomatic incidental nodules without risk factors ¹.