Histologic features of footpad tumors are similar in plasminogen-deficient and control mice. Shown are representative hematoxylin-eosin–stained sections of footpad LLCGFP tumors collected from control (A), Plg– (B), Fib– (C), and Plg–/Fib– (D) mice 14 days after initial transplantation. Note that the overall microscopic features of the tumor tissue were unremarkable within animals of each genotype and suggest no obvious basis for the impediment in tumor growth in Plg– mice. LLCGFP tumors grew as sheets of anaplastic cells that often invaded normal structures, including adjacent muscle and bone. Small areas of necrosis (*) were also present, but these were not appreciably different between animals of each genotype. Dermal surfaces of the footpads are indicated by arrows in panels A to D. Immunohistochemical staining for the endothelial marker PECAM (brown stain) revealed abundant vessels in footpad tumors derived from control (E) and plasminogen-deficient mice (F). Fibrin(ogen) immunostains revealed relatively scant and focal fibrin(ogen) deposition in control (G) and Plg– (H) mice (brown staining highlighted by arrows). Sparse fibrin(ogen) deposition was generally peritumoral or was associated with small areas of necrosis. Sections used for immunohistology were counterstained with hematoxylin.
