Thyroid nodules
A thyroid nodule is a discrete structural lesion within an otherwise normal thyroid gland, found on ultrasound in about 40% of the United States population though palpable in far fewer, and malignant in roughly 5%. Evaluation begins with a thyroid-stimulating hormone (TSH) level and thyroid ultrasonography, and management is surveillance for benign or low-risk nodules, with lobectomy or total thyroidectomy reserved for cytology suspicious for or diagnostic of malignancy.
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What this article covers
- Overview
A structural finding, not a diagnosis: a discrete lesion distinct from surrounding thyroid parenchyma, detected by palpation, incidentally on imaging, or on dedicated thyroid ultrasonography.
- Epidemiology
Rising incidental detection: more thyroid nodules are now found on imaging obtained for unrelated reasons (carotid Doppler, neck or chest CT, PET scan) as cross-sectional imaging use has grown.
- Risk factors
History of ionizing radiation exposure: particularly childhood exposure, such as treatment of childhood cancer or nuclear accident exposure, is the strongest environmental risk factor for malignancy.
- Pathophysiology
Heterogeneous causes within the same presentation: nodules range from benign colloid cysts and inflammatory nodules to follicular adenomas, primary thyroid neoplasms (papillary, follicular…
- Clinical features
Most nodules are asymptomatic: the majority are found incidentally on examination or imaging performed for an unrelated reason.
- Differential diagnosis
Multinodular goiter: multiple discrete nodules on an asymmetric gland rather than a single lesion; per-nodule malignancy risk is similar to a solitary nodule, unlike the smooth, diffuse enlargement of autoimmune thyroiditis.
- Diagnosis
The diagnosis of a clinically significant nodule rests on serum TSH, sonographic risk stratification by the 2015 American Thyroid Association pattern, and fine-needle aspiration biopsy (FNAB)…
- Management
First, triage by TSH and sonographic/cytologic risk; most nodules require no treatment beyond monitoring.
- Complications
Progression to overt hyperthyroidism: an autonomously functioning nodule can enlarge and produce thyroid hormone excess over months to years.
- Prognosis
Excellent for the great majority of nodules: because roughly 95% of thyroid nodules are benign, most patients require only periodic monitoring.
- Prevention
There is no proven primary prevention for sporadic nodules, but limiting unnecessary ionizing radiation exposure, particularly in children, lowers the risk of radiation-induced nodules and later malignancy.
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