Amyloid Goiter, Papillary Thyroid Carcinoma, and Diffuse Thyroid Lipomatosis: A Case Report of a Rare Association.

Amyloid goiter is an extremely rare condition. It results from amyloid infiltration of the thyroid, typically associated with AL (primary) or AA (secondary) amyloidosis, and has occasionally been linked to diffuse fatty infiltration or papillary thyroid carcinoma. The combination of these three conditions is exceptionally rare. We present a case of a 54-year-old male with chronic refractory gout on immunosuppressive therapy who developed a multinodular goiter. A thyroid ultrasound revealed a 45-mm solid hypoechoic nodule classified as European Thyroid Imaging Reporting and Data System 4 (EU-TIRADS 4). Thyroid function was normal. After two non-diagnostic fine needle aspirations, clinical surveillance was chosen. Four years later, the patient presented with thyroid enlargement accompanied by compressive symptoms, which were confirmed as tracheal compression on imaging. A total thyroidectomy revealed amyloid deposition, diffuse lipomatosis, and multifocal papillary microcarcinomas (dominant 0.2 cm). Postoperatively, the investigation for systemic amyloidosis was negative, and the patient demonstrated an excellent clinical and biochemical response, with no recurrence of amyloid deposits. To the best of our knowledge, this is the fourth reported case in the literature of amyloid goiter associated with papillary carcinoma and diffuse thyroid lipomatosis. The case underscores the importance of considering amyloid goiter in patients with significant thyroid enlargement, especially those with chronic inflammatory conditions. Histopathological evaluation is key, and further research is needed to explore potential links between chronic inflammation, amyloid deposition, and thyroid cancer development.