RESUMEN
BACKGROUND Amyloid deposition in the thyroid gland can be primary or secondary and can result in goiter. There have been previous reports of amyloid goiter and thyroid lipomatosis or fatty infiltration. Papillary thyroid carcinoma is the most common thyroid malignancy. We report a rare case of a 54-year-old woman with papillary thyroid carcinoma associated with secondary amyloid goiter and thyroid lipomatosis. CASE REPORT A 54-year-old woman with chronic pyelonephritis and bronchiectasis presented with compressive symptoms due to an enlarged thyroid gland. Thyroid function test results were in the normal range and serum thyroid autoantibodies and serum calcitonin levels were undetectable. Cervical ultrasound showed a diffusely swollen thyroid and a well-defined nodule in the right lobe, of which fine-needle aspiration cytology was suspicious for follicular neoplasm. Computed tomography showed an enlarged thyroid with low attenuation, suggestive of diffuse lipomatosis of the gland. Total thyroidectomy was performed, and a histopathology study indicated the presence of papillary carcinoma and diffuse lipomatosis of the thyroid gland with amyloid deposition. The patient was later diagnosed with secondary amyloidosis. CONCLUSIONS The presentation of secondary amyloidosis as a diffuse goiter with extensive fatty infiltration must be considered in the differential diagnosis of thyroid enlargement, especially those with rapid onset, and particularly in patients with a history of chronic inflammatory disorders or chronic infections predisposing to amyloid deposition. Rarely, differentiated thyroid carcinoma is found within an amyloid goiter and it must be excluded in the differential diagnosis.