Classification and neoplastic risk of discrete thyroid swellings
THE CONTEXT
Discrete thyroid swellings are classified by the clinical findings in the surrounding gland, but clinical examination may miss additional nodules.
Clinical classification
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An isolated or solitary swelling is a discrete swelling in an otherwise impalpable thyroid gland.
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A dominant swelling occurs in a gland with clinical evidence of more general abnormality, such as a palpable contralateral lobe or generalized mild nodularity.
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About 70% of discrete swellings are clinically isolated and about 30% are dominant.
Limits of clinical examination
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Clinical classification is subjective and overestimates the frequency of truly isolated swellings.
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Operation, ultrasonography, CT or MRI often reveals additional clinically impalpable nodules.
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Demonstrating impalpable nodules does not change management of the palpable discrete swelling.
Risk of neoplasia
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Approximately 15% of isolated swellings are malignant, and an additional 30–40% are follicular adenomas.
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The remaining isolated swellings are non-neoplastic and largely comprise colloid degeneration, thyroiditis or cysts.
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The incidence of malignancy or follicular adenoma in clinically dominant swellings is approximately half that in truly isolated swellings, but remains substantial.