Lack of catalytically active PTPN13 promotes mammary tumor invasiveness. A: Mitotic index (box-plot whiskers represent the minimum and maximum values), embolization frequency, and presence of EMT in tumors from MMTV-HER2;PTP-BL+/+ (HER2+/BL-wt) (n=8; panels B, D, F) and MMTV-HER2; PTP-BL△P/△P (HER2+/BL-ΔP) (n=15; panels C, E, G) mice. B&C: Examples of nodules constituting the tumor. Magnification: 2.5x. D&E: Examples of the local invasiveness into the surrounding tumor microenvironment. Magnification: 10x. Yellow arrows show cellular invasion in the stroma, with cells arranged in tubules. These events are rare in HER2+/BL-wt and frequent in HER2+/BL-ΔP tumors. F&G: EMT is increased in the absence of PTP-BL activity (magnification: x40). The white arrowheads show tumor cells undergoing EMT; yellow arrows show the tubules. H: Example of tumor cell embolization in a vein (yellow arrow indicates two tumor cells) from a HER2+/BL-ΔP tumor. At the periphery of the tumor nodule, malignant epithelial cells are infiltrating the microenvironment. Some cells enter vessels. I: Lung section from a HER2+/BL-ΔP mouse with massive embolization of tumor cells (black asterisk) in a large lung blood vessel. Erythrocytes (black arrow) are found only at the periphery of tumor cells. Magnification: x5. J: Metastatic tumor nodule in the lung of a HER2+/BL-ΔP mouse. The nodule, delineated and indicated by a black asterisk, is located between the alveolar spaces, compresses the surrounding tissue, and infiltrates the stroma. Magnification: x20.