KLF4 and neoplasm: IF IHC staining showed the presence of a SOX2+/NANOG+/KLF4+/c-Myc+/OCT− CSC subpopulation within the tumor nests, and a SOX2+/NANOG+/KLF4+/c-Myc+/OCT4− CSC subpopulation and a SOX2+/NANOG+/KLF4+/c-Myc+/OCT4+ CSC subpopulation within the peritumoral stroma.