Pleural amyloidosis mimicking mesothelioma: a clinicopathologic study of two cases.

Two cases of pleural amyloidosis are presented. The patients are two men, 70 and 72 years of age respectively. Neither patient had evidence of systemic amyloidosis. Each presented clinically with symptoms of chest pain and dyspnea. Radiologically, both patients showed diffuse pleural thickening similar to that observed in malignant mesothelioma. In both patients, surgical decortication of the pleura was performed. Histologically, the lesions were characterized by the presence of an amorphous eosinophilic material with focal collections of a lymphoplasmacytic infiltrate. Focal clusters of giant cells were admixed with the lymphoplasmacytic infiltrate. Histochemical stains for Congo red showed strong positive apple-green birefringency. Immunohistochemical studies using kappa and lambda light chains showed polyclonality. The cases discussed herein represent an unusual presentation of amyloid and one that needs to be considered in the differential diagnosis of malignant mesothelioma.