Nodular pulmonary amyloidosis with an unusual protein composition diagnosed by fine-needle aspiration biopsy: a case report.

Nodular pulmonary amyloidosis is rare, but a number of individual cases have been reported in the literature. Radiologically, pulmonary amyloid nodules often mimic cancer and hence require biopsy to obtain a specimen for definitive diagnosis. We describe a case of isolated nodular pulmonary amyloidosis with an unusual amyloid composition that given the patient's clinical history has not been described in the literature to the best of our knowledge, making this case unique. A 58-year-old woman with a history of mixed connective tissue disease was found to have multiple lung nodules on chest computed tomography (CT) that were radiologically suspicious for cancer. A CT-guided percutaneous fine-needle aspiration (FNA) biopsy of one of the nodules was performed. A diagnosis of amyloid was rendered using special stains and polarized light microscopic examination. Immunohistochemical stains revealed that the amyloid comprised beta-2 microglobulin as well as both kappa and lambda light chains. Further work up showed no evidence of systemic amyloidosis. We were successful in rendering an accurate diagnosis of a pulmonary amyloidoma on material procured by CT-guided FNA thus avoiding more invasive procedures. In addition, immunohistochemical staining revealed an unexpected and highly unusual protein composition of the amyloid.