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1 August 2012 - Case of the Week #247
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Thanks to Dr. M. Rizwan Bashir, Aga Khan University Hospital, Karachi, Pakistan, for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.
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Case of the Week #247
A 61 year old woman with hypertension had a diffusely enlarged thyroid gland with the clinical impression of a multinodular goiter. A complete thyroidectomy was performed.
What is your diagnosis?
The amyloid stains with Congo Red (left) and Sirius Red (right), and showed apple-green birefringence under polarized microscopy:
Amyloid goiter is an uncommon disease of amyloid deposits in the thyroid gland associated with goiter. The median patient age is 54 years, but all adults can be affected (Am J Clin Pathol 1995;104:306). It is usually due to primary or secondary AA type amyloidosis, but other causes have been reported (Amyloid 2012 Jun 5 [Epub ahead of print]). Clinically, there is enlargement of the thyroid over several months that may cause respiratory distress, but thyroid function is usually normal. Diagnosis can often be made by fine needle aspiration (Cytopathology 2006;17:262). Occasionally, diagnosis is not made until autopsy.
Grossly, the thyroid is enlarged and white-tan. Histologically, there is diffuse amyloid deposition surrounding thyroid follicles, which may distort the thyroid architecture. Occasional features are foreign body giant cell reaction, fatty metaplasia, fatty infiltration, squamous metaplasia or focal lymphocytic thyroiditis. With the Congo Red stain, the amyloid is salmon colored and demonstrates apple-green birefringence under polarized light.
The differential diagnosis includes medullary thyroid carcinoma, which has prominent amyloid, but also calcitonin positive tumor cells.
Nat Pernick, M.D., President
and Liz Parker, B.A., Associate Medical Editor
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