Abdominal fat tissue aspirates from 12 patients with biopsy-proved
amyloidosis were investigated by different morphologic techniques. By light microscopy, after staining of the fat tissue aspirates with
Congo red and examination with a polarizing microscope, positive results were obtained in nine patients with
amyloidosis, two of the three with primary (
AL) amyloidosis and seven of the nine with secondary (
AA) amyloidosis. By indirect immunofluorescence, using AA antiserum, positive results were obtained in five of the nine cases of
AA amyloidosis (aspirates from these five patients were positive on
Congo red staining). By electron microscopy,
amyloid fibrils were observed in five cases of
amyloidosis (two of the AL and three of the AA type, all positive on
Congo red staining). Although
amyloid was demonstrated less frequently by immunofluorescence and electron microscopy, perhaps because of the small numbers of fat particles examined, it seems that, with
Congo red staining, abdominal fat tissue aspiration is a simple and sensitive method for the diagnosis of
amyloidosis. Immunofluorescence studies allow discrimination between the different types of
amyloidosis. The method could be used in patients in whom other types of tissue biopsy are not recommended because of risks of
bleeding or other problems.