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 VI 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.