Immunohistochemical staining and proteomic analysis showing 2 distinct patterns of amyloid within the cardiac biopsy. (A) Congo red staining of the myocardium. There was an area of dark Congo red staining that also stained with an antibody against λ light chain, but not transthyretin, and an area of lighter Congo red staining that stained with an antibody against transthyretin, but not λ light chain. (B) Transthyretin immunostaining confirming the presence of transthyretin. (C) Immunostaining with an antibody against λ light chain. (D) Proteomic analysis illustrating spectral counts and peptide coverage. Both samples showed the amyloid signature proteins apolipoprotein A-IV, serum amyloid P component, and apolipoprotein. (E) Sample X (left) shows abundant λ light chain (7 spectra, 57% protein coverage in yellow highlight [E]) without any transthyretin and sample Y (right) shows abundant transthyretin (10 spectra, 41% protein coverage in yellow highlight [F]) and some λ light chain (4 spectra, 14% protein coverage). The protein identification probability was >95% in each case.