Amyloid Goiter with Diffuse Thyroid Lipomatosis: Clinicopathologic Insights from a Five-Patient Case Series

Background/Objective Amyloid goiter ,defined as the excess deposition of amyloid within the thyroid gland in such quantities to produce a clinically apparent goiter, is a very rare manifestation of systemic amyloidosis. The coexistence of diffuse thyroid lipomatosis with amyloid goiter is exceptionally uncommon and can pose diagnostic challenges. Case presentation We report five patients (mean age 49.4 ± 9.2 years; four females) who presented with rapidly enlarging bilateral goiters and compressive symptoms. Thyroid function varied, with three patients euthyroid, one hypothyroid, and one with treated Graves' disease who presented with goiter-related symptoms rather than thyrotoxicosis. Preoperative imaging demonstrated diffuse thyroid enlargement with heterogeneous echotexture and varying degrees of fatty infiltration. Fine needle aspiration cytology was reported as benign in four available samples out of 5 cases. All patients underwent total thyroidectomy for compressive symptoms and suspicion of malignancy. Intraoperatively, the glands were enlarged, soft, friable, and characteristically yellowish, with prominent fatty infiltration. Identification of the parathyroid glands was challenging due to surrounding adipose tissue. Notably, amyloid deposition involving adjacent parathyroid tissue was observed in one patient. Histopathologic examination revealed diffuse adipocytic metaplasia with extracellular amorphous eosinophilic deposits that were Congo red–positive and demonstrated apple-green birefringence under polarized light, confirming amyloid deposition. Immunohistochemistry identified AA amyloidosis in three patients and AL amyloidosis in one. Discussion Amyloid goiter with diffuse thyroid lipomatosis represents a rare clinicopathologic entity. It may mimic other causes of rapidly enlarging goiter, and preoperative diagnosis is often not possible with routine cytology alone. Recognition of this pattern is important for appropriate management and systemic evaluation. Conclusion Amyloid goiter should be suspected in all patients with a progressive, rapidly growing bilateral thyroid enlargement with concomitant inflammatory processes or plasma cell dyscrasias. Surgical management is both diagnostic and therapeutic, and systemic evaluation is essential.