Immunohistochemical analyses of sections of muscle tissue and a spontaneous tumor. (A) Tissue section of muscle with no cell injection. (B) Tissue section of muscle received myoblasts carrying pdLMe4βAhIXm1. Tissue sections in panels A and B were stained with hFIX monoclonal antibody followed by counter-staining with hemotoxylin (×630). Brownish-red color indicates the presence of hFIX. (C) Section of the tumor from a group 4 mouse stained with H & E (×500). The fibrosarcoma cells are small and spindle-shaped; one large muscle fiber is on the left. (D) Tumor section stained with Masson trichrome shows small spindled cells of fibrosarcoma and the collagen produced by the neoplasm in blue color; several muscle fibers are red or purple-red in color and large in size (×500).