By Dr Vijay Panicker
Head of Department Endocrinology, Sir Charles Gairdner Hospital
Thyroid nodules are common. They are found in two to six percent of the general population by palpation and 19 to 35 percent by ultrasound. They are frequently picked up when patients are having investigations for other reasons, including by carotid dopplers, MRI, CT and PET scan. Whether they are picked up incidentally or present with symptoms, they all need to be assessed.
There are three ways nodules cause problems; autonomous production of thyroid hormones causing hyperthyroidism, compressive symptoms if very large (and retrosternal), and thyroid cancer. Each nodule is said to have a five to eight percent chance of malignancy. This is how I would work up a new thyroid nodule:
- History: Important features are family history of thyroid cancer, and exposure to radiation. Exposure to radiation may be from radiotherapy for breast or neck cancer, or general exposure such as associated with nuclear disaster.
- Thyroid function: Test TSH, and if low add T4 and T3. Cancer nodules rarely produce thyroid hormones. Therefore, if a patient has a low TSH the next step is a thyroid uptake scan (not biopsy). If the nodule is hot it can be assumed to be benign without biopsy. I also do thyroid autoantibodies as it is useful to know if patients have high antibody levels (such as with autoimmune thyroid disease) as they will often have a lymphocytic cellular picture on FNA
- Ultrasound: There are features on ultrasound that can stratify the risk of the nodule and will therefore dictate whether and what size it should be biopsied. A good thyroid radiologist will report these and often rate the risk of the nodule according to one of the rating systems (such as ACR-TIRADS). If the size and important features of the nodules >1cm are not reported I suggest you contact the radiologist.
- Fine needle aspiration (FNA): Should be done if the ultrasound appearances are sufficiently worrying and the nodule is large enough. If the nodule is easily palpable the pathologists can do this and ensure they get a good sample. Otherwise it is done under ultrasound guidance. It is important to counsel the patient that 15 to 35 per cent of these come back indeterminate; due to lack of sample, too bloody, etc. It is therefore important to know what the risk is before biopsy to guide you if the biopsy is unsuccessful (i.e. should you re-biopsy, operate or observe).
Benign FNAs are 98 to 99 per cent accurate and can be left, although my practice is to repeat an US (and TFTs) if the nodule was very large or had suspicious features. If FNA is malignant (or suspicious of malignancy), refer to a thyroid surgeon for thyroidectomy.
Note that most early recurrences are due to incomplete resection rather than rapid recurrence and therefore I only refer to high volume thyroid surgeons.
A follicular neoplasm or suspicious follicular neoplasm needs referral to a surgeon for hemithyroidectomy as cytology cannot distinguish between follicular adenoma and follicular carcinoma. The majority will still be benign. Indeterminant lesions are best referred to a thyroid surgeon or endocrinologist, as it is worthwhile considering the pre-test risk (history, ultrasound features) and patient anxiety to decide if further biopsy or surgery is the next best option.
I tell patients that > 90 per cent of thyroid cancers are differentiated thyroid cancers of which 95 per cent have very good prognosis (slow growing, slow spreading and don’t shorten life expectancy). There is time to clarify the diagnosis (such as waiting to repeat biopsy) and I tend to err on the side of conservatism to avoid unnecessary surgery, which is rarely the case with other malignancies.
Finally, there is no value in evaluating nodules <1 cm except in a very high-risk patient, or in measuring serum thyroglobulin in someone who has a thyroid.
See also the “Thyroid Nodules and Goitre” HealthPathway.