Vasculogenic mimicry is associated with poor survival in patients with mesothelial sarcomas and alveolar rhabdomyosarcomas

Increased vasculogenesis must occur for tumors to develop and be maintained. Normally, vascular networks are composed of tube structures lined with endothelial cells. However, the vascular networks that form around some highly aggressive cancers possess a distinct tubular structure, resulting from a process called vasculogenic mimicry (VM) that does not have endothelial cells. In these tubes, the tumor cells function as endothelial cells. VM has been found in several different types of cancers such as melanoma, breast cancer, prostate cancer, and ovarian cancer. We hypothesized that it also plays a role in the development and metastasis of sarcomas, which are typically aggressive tumors. We used immunohistochemical analyses and electron microscopy to identify VM channels in 81 synovial sarcomas (SSs), 37 mesothelial sarcomas (MSs), 69 alveolar rhabdomyosarcomas (ARs), and 190 melanomas, which were used as a comparison group. The presence of red blood cells in the vessels was also used as a criterion for VM. Because VM is generally believed to be associated with aggressive cancers, we tested whether the presence of VM channel correlated with patient survival. We detected VM channels in 11 of 81 SSs (13.6%), 10 of 37 MSs (27.0%), 13 of 69 ARs (18.8%), and 10 of 190 melanomas (5.3%). The VM channels were not distributed uniformly in the tumor tissues but appeared in patches. In addition, VM channels were most frequently observed in the boundary regions between the tumor and adjacent normal tissues. The tumor cells around the VM tubes frequently stained positive for collagen IV and CD31 and were also PAS-positive. In contrast, tumors that lack VM channels generally also lack these markers. Our studies of the correlation of VM with patient survival also showed that VM correlated with shorter survival in patients with MS (P=0.03), AR (P=0.03), and melanoma (P=0.04), but not with SS (P=0.76). Our studies demonstrated that VM channels are a clinically important phenotype in sarcomas and melanomas. Our findings also suggested that a subpopulation of tumor cells possess features of both endothelial cells that line the vessels and mesenchymal cells that secrete the extracellular matrix required for the vascular infrastructure.