Endocrine Abstracts

Introduction: Amyloid accumulation in the thyroid gland leading to a clinically detectable mass is a rare clinical entity. The diagnosis of thyroid amyloidosis can be confused clinically as well as cytologically with both colloidal goiter or neoplastic processes of the thyroid. We report a case of thyroid amyloidosis that was initially misinterpreted as medullary thyroid carcinoma (MTC) clinical and cytological examination.

Case: A 24 years old man with chronic renal failure admitted to our hospita with rapidly progressive enlargement of a neck mass. He was suffering from renal failure for at least 10 years secondary to nephrolithiasis and was on 3 day/week hemodialysis after the rejection of renal transplantation 2 years before. He had dysphagia and dyspnea for about 5 months. Further workup demonstrated multinodular goiter with compressive symptoms and substernal extension. He had multiple nodules with the largest diameter of 80 mm in ultrasonography. Serum TSH was1.68mIU/L (0.27–4.2), free T4 was1.01ng/dL (0.9–1.7), free T3 was2.84ng/dL (1.8–4.6) and thyroglobulin was 758 ng/mL (0–78). Anti-thyroglobulin and anti-thyroid peroxidase antibodies were negative. His calcitonin level was high which was suggestive for possible diagnosis of MTC (12.6 pg/mL normal:2-8 pg/mL). Fine needle aspiration cytology of the largest nodule displayed MTC. 24 hour urine catecholamine levels were within the normal range and computerized tomography of adrenal glands revealed no pathology. Total thyroidectomy was performed and the final histopathological diagnosis was thyroid amiloidosis.

Conclusion: Although amyloid deposition in thyroid is a well known fact in MTC, it should be remembered that it is not a histological finding exclusive of this disease. In patients with a rapidly enlarging thyroid gland presenting with dysphagia, dyspnea, or hoarseness, amyloid goiter should be included in the differential diagnosis particularly when the patient has a chronic disease that might be associated with amyloidosis.