TIE2 immunohistochemistry of human cancer cryosections. After TIE2 immunostaining, the sections were counterstained with hematoxylin and eosin and shown at lower (left) or higher (right) magnification. (A) Colon adenocarcinoma. In addition to vascular ECs (arrowheads), TIE2 staining highlights the presence of stromal mononuclear elements morphologically consistent with monocytes (arrows). These cells appear inhomogeneously distributed, with foci of high density (arrows). (B) Gastric undifferentiated adenocarcinoma. Many TIE2⁺ mononuclear cells are found in the tumor stroma (arrows). Blood vessels are indicated by arrowheads. (C) Pancreatic adenocarcinoma. The majority of TIE2⁺ structures in the left panel are blood vessels (arrowheads). An individual TIE2⁺ mononuclear cell is shown (arrow) in the right panel.