Metastases: mechanisms, pathways, and cascades.

Metastases are the major cause of treatment failure in cancer patients. Sixty percent of patients with newly diagnosed solid tumors (excluding skin cancers other than melanoma) have clinically evident or microscopic metastases when the primary tumor is diagnosed [1]. Dissemination of malignant cells throughout the body and their survival to form secondary growths constitute a complicated process dependent on both host and tumor properties. This review outlines the mechanisms involved in the metastatic process, the pathways of tumor spread throughout the body, and the common routes used by various tumors.