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17 February 2011 – Case of the Week #197
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Case of the Week #197
An 85 year old woman was admitted with shortness of breath and chest pain. She had been given a diagnosis of inoperable lung cancer several years previously on the basis of multiple lung nodules on chest x-ray.
The postmortem examination revealed an acute myocardial infarction involving the posterior mitral valve papillary muscle and multiple waxy yellow/brown pulmonary nodules. A fine needle aspiration of the lung nodule was obtained, and stained with the Romanowsky method.
Fine needle aspiration of lung nodule
Lung nodules - H&E
What is your diagnosis?
Nodular pulmonary amyloidosis
The fine needle aspirate showed a honeycomb arrangement of benign bronchial epithelial cells next to amorphous material. Sections with Congo-Red staining and polarized microscopy show colloid cracking and apple-green bifrefringence of the amorphous material, diagnostic of amyloid deposition:
Pulmonary amyloid often presents in an asymptomatic elderly patient with a nodule on chest Xray, but no evidence of systemic disease. It may be due to a chronic inflammatory condition (TB, HIV, connective tissue disorder), or be associated with a plasma cell dyscrasia or lymphoproliferative disorder.
Pulmonary amyloid can be divided into 4 categories: vascular (not a serious clinical problem), nodular bronchial, nodular parenchymal or diffuse alveolar septal. The nodular types can have multiple lesions and may simulate malignancy, as in this case. Diffuse alveolar septal cases may cause severe pulmonary impairment with a poor prognosis. In all categories, the amyloid material is usually composed of AL type protein.
Histologically, the nodules are usually well circumscribed, with amorphous pink amyloid material. T cells, plasma cells and granulomatous inflammation are common. Calcification and ossification are also common.
The differential diagnosis includes marginal zone lymphoma/MALT or SLL with amyloid production (Mod Pathol 2000;13:934) as well as hyalinizing granuloma (no amyloid is actually present). Amyloid-like pulmonary nodules have been described with and without systemic light chain disease (Am J Clin Pathol 2004;121:200). Electron microscopy shows dense granular extracellular deposits, but without the fibrillary characteristics of amyloid.
Patients with nodular amyloid, as in this case, typically have a good clinical course. Although treatment of associated conditions may be indicated, the amyloid nodules are typically indolent.
Nat Pernick, M.D., President
and Liz Parker, B.A., Associate Medical Editor
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