Amyloid deposits in lymph nodes: a morphologic and immunohistochemical study.

In a series of approximately 80,000 lymph nodes, amyloid deposition was found in 18; 12 of those nodes were selected, on the basis of availability of specimens, for investigation by immunohistochemical typing to identify the protein of origin and by correlation with morphologic criteria and clinical information. Four patterns of amyloid deposition were identified: lymph node vessel involvement, follicular deposition, diffuse deposition, and a combination of follicular and diffuse deposition. All cases were classified immunohistochemically with the amyloid type-specific antisera anti-AA, anti-A lambda, anti-A kappa, anti-ASc1, and anti-AF. Immunoglobulin-derived protein (AL) in lymph nodes was found in every case of isolated amyloidosis, lymphoplasmacytic/lymphoplasmacytoid immunocytoma, plasmacytoma, and idiopathic amyloidosis. Among the cases of AL amyloidosis were nine of A lambda and one of the A kappa type. AA protein was present in two cases of reactive systemic amyloidosis. There was no useful morphologic correlation with the immunohistochemically identified amyloid types.