What does a thyroid ultrasound and TIRADS report actually mean?
A thyroid ultrasound report can be hard to read and frightening. This guide makes everything easy to understand.
When is a thyroid ultrasound ordered?
Thyroid ultrasound is the first investigation when there is a palpable lump on the neck, the neck looks uneven, there is a goiter, TSH is elevated, there is a family history of thyroid cancer, the neck has previously been irradiated, or when a thyroid nodule is found incidentally on a CT, MRI, or PET scan. Ultrasound is also used to monitor a known benign or treated thyroid disease. The examination is safe during pregnancy as well, since no ionizing radiation is used.
What is assessed on a thyroid ultrasound?
A thyroid ultrasound report typically evaluates the size of the thyroid, echogenicity (compared with the surrounding neck muscles), blood flow on Doppler, and the uniformity of the tissue structure (homogeneous or heterogeneous). A diffuse heterogeneous hypoechoic pattern suggests autoimmune thyroiditis (Hashimoto's or Graves' disease); a diffusely enlarged and hypervascular thyroid is characteristic of Graves' disease; an atrophic, that is, reduced-volume thyroid, is typical of advanced or chronic Hashimoto's disease.
Nodules
For each thyroid nodule, the following features are described: 1. Cystic (fluid-filled), spongiform, mixed cystic-solid, or solid. 2. Echogenicity: hypoechoic, hyperechoic, isoechoic, or markedly hypoechoic compared with the neck muscles. 3. Shape: wider than tall (more of a benign feature) or taller than wide (a suspicious feature). 4. Margins — smooth, ill-defined, lobulated/irregular, or extending outside the thyroid (a suspicious feature). 5. Echogenic foci: none, comet-tail artifacts representing colloid foci (benign), a peripheral rim of calcification, coarse macrocalcifications, or fine punctate microcalcifications (a suspicious feature). 6. Size — the three largest dimensions of the nodule. 7. Blood flow on Doppler: no flow, peripheral, or intranodular.
TIRADS classification
The European Thyroid Association (EU-TIRADS) system divides thyroid nodules into categories 1–5 based on ultrasound features and the risk of malignancy. TIRADS 1 — normal thyroid, no nodules present. TIRADS 2 — benign finding; typically a cystic or spongiform nodule. The risk of malignancy is very low. TIRADS 3 — low-risk nodule; usually an isoechoic or hyperechoic solid nodule without suspicious features. The risk of malignancy is about 2–4%. TIRADS 4 — intermediate-risk nodule; usually a mildly hypoechoic solid nodule without high-risk features. The risk of malignancy is about 6–17%. TIRADS 5 — high-risk nodule; the risk of malignancy is approximately 26–87% when at least one high-risk ultrasound feature is present: marked hypoechogenicity, irregular or lobulated margins, taller-than-wide shape, or punctate microcalcifications.
ACR-TIRADS scoring system
The American College of Radiology (ACR-TIRADS) gives points across five categories and then assigns a score from TR1 (benign) to TR5 (highly suspicious). The system is used in many countries. In practice, both systems make the same decisions about biopsy.
When is it time to biopsy a nodule?
TIRADS 5: FNA when the nodule is 10 mm or larger. TIRADS 4 — when the nodule is 15 mm or larger. FNA is required for TIRADS 3 only if the nodule is at least 20 mm, and is not required for TIRADS 2 or 1. The ACR-TIRADS criteria are the same: TR5 must be at least 10 mm, TR4 at least 15 mm, and TR3 at least 25 mm. A biopsy should be taken from any suspicious lymph node, regardless of the status of the index nodule. The Bethesda system (I–VI) reports the FNA results.
Follow-up
Nodules that appear benign (TIRADS 2–3) and do not meet FNA criteria initially require ultrasound every 12–24 months; if the findings remain stable, the monitoring intervals can be extended. For TIRADS 4 nodules, a follow-up ultrasound is usually performed after 12 months. For high-risk TIRADS 5 nodules that do not reach the biopsy size threshold, a repeat ultrasound is usually performed within 6–12 months. When the fine-needle biopsy result is benign, the ultrasound is usually repeated after 12–24 months. If the nodule remains unchanged, the interval between further examinations can be lengthened. A repeat fine-needle biopsy is indicated when the nodule grows: a 20% increase in at least two dimensions or at least a 50% increase in volume.
Medical disclaimer. This article is for general educational purposes and does not replace consultation, diagnosis or treatment by a qualified healthcare professional. Always discuss your individual situation with your own doctor.