A key feature of malignant cells is their capacity to invade surrounding tissue and metastasize to distant sites (1 ,2 ). The process of metastasis involves a complex series of events that include cell transformation and proliferation, vascular invasion at primary growth site with associated basement membrane degradation, transport through capillary or lymphatic vessels, attachment of tumor cells to endothelial or subendothelial structures at the secondary site, and the subsequent growth of the secondary tumor mass (3 ).
