Masson’s trichrome staining of orthotopic, late-stage MMTV-PyMT mammary tumors treated according to an extended (9 weeks) treatment schedule. Collagen’s blue staining demonstrates abundant fibrotic tissue and scant tumor cells in 3.19.3-treated tumors (day 78). Left panels show tumor periphery. Scale bars, 600 mm (left panels) and 300 mm (right panels). Images are representative of five 3.19.3-treated (day 78) and three control IgG-treated (day 48) tumors. Reproduced with permission .