Metastasis is the spread of a disease from one organ or part to another non-contiguous organ or part. Only malignant tumour cells and infections have the capacity to metastasise. Cancer cells can "break away" from a primary tumour, penetrate into lymphatic and blood vessels, circulate through the bloodstream, and grow in a distant focus (metastasise) in normal tissues elsewhere in the body. Metastasis is considered a hallmark of malignancy. All tumours can metastasise albeit to varying degrees, barring a few exceptions (eg. Glioma and Basal cell carcinoma never metastasize). When cancer cells spread to form a new tumour, it is called a secondary, or metastatic tumour, and its cells are like those in the original tumour. This means, for example, that if breast cancer spreads (metastasizes) to the lung, the secondary tumour is made up of abnormal breast cells (not abnormal lung cells). The disease in the lung is then called metastatic breast cancer (not lung cancer). Only malignant tumour cells and infections have the capacity to metastasize. This book presents the latest research in the field from around the world.