Local synthesis of amyloid fibril precursor in AL amyloidosis of the urinary tract

An amyloid tumor localized to the urethra was resected and shown by immunohistochemistry to contain fibril deposits that stained with antisera specific for lambda(VI) immunoglobulin light chain. The amino acid sequence of the fibril protein was homologous to lambda(VI). Positive staining of subepithelial plasma cells with lambda(V)I specific monoclonal antibody was consistent with the hypothesis that the fibril precursor light chain protein is synthesized and processed locally to give this type of localized amyloidosis.