The authors observed that xenografted tumor tissues incubated with the ferrimagnetic H-ferritin nanoparticles showed a brownish color due to the nanozyme-catalyzed oxidation of 3,3'-diaminobenzidine tetrahydrochloride substrates under the presence of excessive H2O2, while the normal tissues were stained purple by hematoxylin (Cai et al., 2015). This evidence concerns the gene FTH1 and neoplasm.