A rapidly growing thyroid mass, particularly one that is solid and fixed, raises concern for anaplastic carcinoma and requires accurate tissue diagnosis.
Diagnostic concern and differential
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A rapidly growing, solid, fixed thyroid mass should be considered at risk of anaplastic carcinoma.
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Anaplastic carcinoma may be difficult to distinguish from thyroid lymphoma or occasionally thyroiditis.
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Core or even open biopsy may be necessary to establish a confident diagnosis.
Why the distinction matters
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Anaplastic carcinoma is rapidly fatal, and palliative measures are generally recommended.
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The confounding disease processes may respond to therapy, making accurate differentiation critical.