Accurate risk-stratification of malignancy risk of thyroid nodules best occurs with integration of clinical factors, ultrasound features and cytology results1. An illustrative case is presented.
A 53 year old female presented for review of an incidentally discovered thyroid nodule. Clinical examination revealed a firm thyroid nodule on the right without lymphadenopathy.
Cytology, performed prior to specialist review, showed a cellular aspirate with atypical follicular cells in sheets, without colloid, classified as Bethesda IV “Suspicious for Follicular Neoplasm”.
Specialist neck-ultrasound identified a large right upper pole thyroid nodule (23x21x24mm) which was markedly hypoechoic. The margin was grossly lobulated. There was no extrathyroidal extension or calcification. Vascularity was normal. A capsule was not seen.
Ultrasound features were not typical of a follicular lesion, which are usually isoechoic with an identifiable capsule. Marked hypoechogenicity of a solid lesion suggests dense hypercellularity, and gross lobulations are a high-risk feature, suggesting invasion. Together with the cytology findings (cellular aspirate, Bethesda IV) and clinical findings (firm nodule) a pre-operative diagnosis of follicular thyroid cancer (FTC) was made.
Histopathology revealed a 25mm widely-infiltrative lesion with gross lobulations and no capsule. Microscopy showed mixed infiltrative and expansile growth pattern, fused microfollicular structures and areas of solid tumour cell sheets, peripheral irregular infiltrating strands of tumour cells and perineural and lymphovascular invasion, consistent with an unencapsulated, widely invasive FTC.
This case illustrates that synthesis of complementary information obtained from clinical presentation, cytology and ultrasound yields greater diagnostic information than any modality in isolation. Lobulation and hypoechogenicity are typical high risk features on ultrasound, although not usually associated with follicular pathology, and are classically demonstrated on both ultrasound and gross imaging in this case.