Thyroid nodules are extremely common. Ultrasound detects them in a substantial proportion of adults, particularly women and older people, and the majority are found incidentally on scans done for something else entirely.
The great majority are benign. The purpose of assessment is to identify the small number that are not, without subjecting everyone else to unnecessary surgery.
What the Thyroid Does
The thyroid is a butterfly shaped gland at the front of the neck that produces hormones controlling metabolic rate.
A goitre is simply an enlarged thyroid, which may be diffuse or contain nodules. It may be associated with normal, over or underactive thyroid function, so enlargement and function are separate questions.
Iodine deficiency was historically the main cause of goitre in India, and salt iodisation has reduced it considerably, though it persists in some regions. Autoimmune thyroid disease is now a more common cause in urban populations.
How Nodules Are Found
Most are found in one of three ways.
- Noticed by the patient as a visible or palpable lump
- Found by a doctor during examination
- Discovered incidentally on a scan of the neck or chest done for another reason
The last category has grown considerably as imaging has become more common. An incidentally found small nodule in someone with no symptoms usually needs only assessment and reassurance.
The Assessment Sequence
Two things are established first: whether the thyroid is functioning normally, and what the nodule looks like.
- TSH blood test: the starting point. A low TSH suggests an overactive nodule, which is almost always benign and is managed differently
- Ultrasound: describes size, structure and features suggesting risk. This is the key investigation
- Fine needle aspiration: a biopsy using a thin needle, done for nodules meeting criteria based on ultrasound features and size
- Thyroid scan: used where TSH is low, to identify a hot nodule
The order matters. A nodule with a suppressed TSH is likely to be a hot, autonomously functioning nodule, and biopsy is generally unnecessary in that situation.
Ultrasound Features That Raise Concern
Radiologists use standardised scoring systems, and certain features increase suspicion.
- Marked hypoechogenicity, meaning the nodule appears much darker than surrounding tissue
- Irregular or infiltrative margins
- Microcalcifications, small bright specks within the nodule
- Taller than wide shape on cross section
- Extension beyond the thyroid capsule
- Abnormal appearing neck lymph nodes
Conversely, purely cystic nodules and spongiform nodules are almost always benign and often need no biopsy regardless of size.
Size alone is a poor predictor. A large nodule is not more likely to be malignant than a small one, though large nodules may need treatment for pressure symptoms.
Clinical Features Increasing Risk
Certain aspects of the history and examination raise concern independently of imaging.
- A hard, fixed nodule that does not move on swallowing
- Rapid growth over weeks
- Hoarseness of voice, suggesting nerve involvement
- Difficulty swallowing or breathing
- Enlarged neck lymph nodes
- Previous radiation exposure to the head or neck, particularly in childhood
- A family history of thyroid cancer or associated genetic syndromes
- Age under twenty or over sixty
- Male sex, since nodules are less common in men but more often malignant
Hoarseness with a thyroid nodule always warrants prompt assessment, since it can indicate involvement of the nerve supplying the vocal cord. Our ENT department examines the vocal cords in this situation.
What the Biopsy Result Means
Results are reported in standard categories, and the terminology causes confusion.
- Benign: the most common result. Usually followed with periodic ultrasound rather than surgery
- Malignant: requires surgery
- Suspicious for malignancy: surgery usually recommended
- Indeterminate or follicular lesion: the difficult category, where the sample cannot distinguish benign from malignant. May need repeat biopsy, molecular testing or diagnostic surgery
- Non diagnostic: insufficient cells, requiring a repeat
The indeterminate result is frustrating for patients. It does not mean cancer, and in most such cases the eventual finding is benign, but the distinction often cannot be made without removing the nodule.
Thyroid Cancer Is Usually Very Treatable
If a nodule does turn out to be malignant, the outlook is generally excellent, which is worth stating plainly because the word cancer causes disproportionate fear here.
Papillary thyroid cancer, the most common type, has excellent long term survival, particularly when found early and in younger patients. Treatment involves surgery, sometimes followed by radioactive iodine, and lifelong thyroid hormone replacement.
Medullary and anaplastic types behave differently and are much less common. Medullary cancer can be hereditary, which is why family history matters.
Very small low risk papillary cancers are sometimes managed with active surveillance rather than immediate surgery, which is a reasonable option in selected patients.
When Surgery Is Needed for Benign Disease
Malignancy is not the only reason to operate.
- A large goitre causing pressure on the windpipe or oesophagus, with breathlessness or swallowing difficulty
- Extension of the goitre behind the breastbone
- An overactive nodule not controlled by medication or radioactive iodine
- Cosmetic concern where the goitre is large and visible
- Indeterminate biopsy requiring definitive diagnosis
Risks of thyroid surgery include injury to the nerve supplying the vocal cord, causing hoarseness, and damage to the parathyroid glands, causing low calcium. Both are uncommon in experienced hands and should be discussed before consenting.
After total removal, lifelong thyroid hormone replacement is required, which is straightforward but must be taken consistently. Our endocrinology department manages follow up.
A thyroid nodule found on a scan is usually nothing to fear. Get a TSH and a proper ultrasound, and let those determine whether biopsy is needed rather than the size alone. Hoarseness, rapid growth or a hard fixed lump are the features that warrant prompt attention.
Our endocrinology department at T. Nagar assesses thyroid nodules and goitre.
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