Ki-67 antigen retrieval in formalin- or ethanol-fixed, paraffin-embedded tissues: An enhancement method for immunohistochemical staining with autoclave treatment

We developed a new immunohistochemical method to visualize Ki-67 antigen in formalin-fixed, paraffin-embedded sections of bone tumors. The method uses autoclave pretreatment of sections immersed in citrate buffer before incubation with the MIB 1 antibody, which reacts with the Ki-67 gene product. MIB 1 antibody showed strong and discrete staining of cell nuclei in proliferating tumor cells. This method also retrieved antigen in paraffin-embedded sections of alcohol-fixed tissue. Therefore, tissues previously considered unsuitable for immunohistochemical analysis can be studied after autoclave treatment.