Vasculogenic mimicry: a new prognostic sign of human osteosarcoma.

Vasculogenic mimicry (VM), a formation of nonendothelial microvascular channels, has been generally recognized as a new pattern of neovascularization in aggressive malignancies. However, whether VM is present and clinically significant in osteosarcoma remains unknown. We identified VM by CD34/periodic acid-Schiff double staining of osteosarcoma specimens before chemotherapy and investigated its prognostic implications. Tumors were also immunohistochemically stained for focal adhesion kinase (FAK) and migration inducing gene 7 (Mig-7) to determine whether these markers are associated with the occurrence of VM. VM was found in 15 of 66 osteoblastic-type osteosarcoma samples (22.7%), and the incidence of VM did not differ with respect to patient sex, age, tumor size, tumor site, surgical type, or histologic response to preoperative chemotherapy. However, Kaplan-Meier survival analysis determined that the presence of VM and the tumor necrosis rate after preoperative chemotherapy are associated with both the overall survival (P = .011 and P = .040, respectively) and metastasis-free survival (P = .002 and P = .045, respectively). Furthermore, Cox proportional hazards analysis showed that the presence of VM and the histologic response to preoperative chemotherapy were independent indicators for both poor overall survival (P = .007 and P = .024, respectively) and poor metastasis-free survival (P = .002 and P = .027, respectively). The expression level of FAK and Mig-7 were higher in the VM group than the non-VM group (P = .017 and P = .021, respectively). These results demonstrate the presence of VM in osteoblastic osteosarcoma and suggest that VM is an unfavorable prognostic factor with FAK and Mig-7 expressions as a potential mechanism of VM formation in osteosarcoma.