A Rare Case of Amyloid Goiter Suspected to Be Malignant on Imaging Findings

A 67-year-old man was diagnosed with Hashimoto's thyroiditis, and replacement therapy with levothyroxine was initiated. Ten years later, although the patient was euthyroid, ultrasonography showed an increase in goiter size and a significant decrease in overall echogenicity with scattered high-echo areas. Computed tomography revealed diffuse low-density areas with no contrast effect in the thyroid parenchyma and partial high-density areas, indicating possible malignancy. However, a core needle biopsy revealed an amyloid light-chain (AL) κ-type amyloid goiter. Because serum immunoprecipitation electrophoresis showed IgG κ-type M-protein, the diagnosis was secondary amyloidosis. It is important to consider amyloid goiter with imaging findings, as in this case.