Diagnostic studies for FAP. (A-C) Histopathological images of a biopsy specimen of the duodenum obtained from an FAP ATTR Val30Met patient. (A) Congo red staining. (B) Polarized light. (C) Immunohistochemistry with an anti-TTR antibody. (D) Sequence analysis of the TTR gene. (E) SELDI-TOF MS analyses of serum TTR from an FAP ATTR Val30Met patient. The molecular weight of MT TTR is 32 m/z higher than that of WT TTR.