Immunochemical microanalysis of amyloid proteins in fine-needle aspirates of abdominal fat.

Diagnosis of systemic amyloidosis by fine-needle aspiration biopsy of abdominal fat is well established. A complete diagnosis now must include determination of the chemical type of amyloid. Microextracts of amyloid proteins from 11 Congo red-positive aspirate samples were analyzed with immunochemical methods. There was correspondence of the results obtained by immunohistologic and Western blotting analyses in 3 of 4 specimens with kappa light chain amyloid, 5 of 6 with lambda amyloid, and 1 with amyloid A. The method provides rapid and reliable diagnostic information necessary for classification of the chemical type of amyloid required for initiation of specific modes of therapy, with little discomfort to the patient.