Invasion and metastasis: new approaches to an old problem.

The progressive process of tumor invasion and generation of metastases is the primary cause of death for most patients with cancer. Recent advances have led to identification of novel sites for investigation and intervention. These advances include the definition of regulatory components of the metastatic cascade and characterization of the processes of angiogenesis, adhesion, proteolysis, and migration. This further understanding of the complex process of cancer progression has allowed the development of new diagnostic tools and potential therapeutic approaches.