Thyroid nodules are abnormal growths within the thyroid gland. They may be benign or they may be malignant (only around 5% are thyroid cancer). Often they are found incidentally (thyroid incidentaloma) during imaging, and should be investigated appropriately. Nodules are actually present in around 50% of the population but are not palpable (only 5-10% are palpable).
🔢 Classification
Benign nodules
These make up 95% of all nodules.
- Thyroid adenomas
- Follicular adenomas - we shall discuss this in more detail below.
- Hürthle cell adenoma
- Toxic adenoma - discussed here.
- Papillary adenoma
- Thyroid cysts/colloid cysts
- Multinodular goitre
- Hashimoto’s thyroiditis
Malignant nodules
- Papillary carcinoma - this is the most common form of thyroid cancer.
- Follicular carcinoma
- Medullary carcinoma
- Anaplastic carcinoma
- Hürthle cell carcinoma
- Lymphoma
- Metastatic carcinoma - albeit rare, they may derive from breast or renal cancers.
Follicular adenoma is the most common type of thyroid nodule. As the name implies, it arises from the follicular cells of the thyroid gland. It is usually a non-functional adenoma.
😷 Presentation
- Slow-growing solitary nodule
- Asymptomatic
- There is a 1% chance of it turning into a toxic adenoma which would result in thyrotoxicosis.
🔍 Investigations
- TFTs - typically normal.
- Fine needle aspiration cytology (FNAC) - not as useful as it cannot differentiate between follicular adenoma and carcinoma.
- Surgical excision (hemithyroidectomy) + histological analysis - normal follicular structure without tumour invasion into the surrounding tissue.
🧰 Management
- Surgical excision + histological analysis
- If no evidence of cancer → no further treatment required.
- If follicular cancer is identified → total thyroidectomy + adjuvant chemotherapy.
Most commonly, thyroid cysts happen due to cystic degeneration of thyroid tissue or involution of an adenoma.
- Simple cysts are exclusively fluid-filled nodules lined by benign epithelial cells.
- Complex cysts are partly solid and partly cystic and carry a 5–10% risk of malignancy.
😷 Presentation
- Palpable thyroid nodule
- Haemorrhage into a cyst → pain and rapid enlargement of the nodule
- A large cyst or extensive haemorrhage can cause compression symptoms (e.g., hoarseness, dysphagia).
🔍 Investigations
- TFTs - normal
- Thyroid ultrasound - shows cystic components as anechoic, and may show them being mixed with solid components.
- FNAC - diagnostic FNAC is unnecessary for fully cystic nodules. For partly cystic nodules, FNAC can be therapeutic - consider it if:
- Size is ≥1.5 cm & low risk pattern (eccentric solid component)
- Size is ≥2 cm and very low risk pattern
🧰 Management
- Benign cysts
- Asymptomatic cysts - observe.
- Large or symptomatic cysts (or patient preference)
- 🥇 FNAC with/without ethanol ablation. Recurrence rate after aspiration remains very high (at 90%).
- 🥈 Surgery may be considered if aspiration is not effective.
- Malignant cysts - manage the same as thyroid cancer.
- New cyst during pregnancy - thyroid US ± FNAC
- Thyroid nodule + any of the following:
- Male sex
- <14 years old or >70 years old
- History of radiation to the head/neck
- Family history of MEN2 or thyroid cancer
- Solid nodule on thyroid ultrasound
- Cold nodule on thyroid scintigraphy
🔍 Investigations
