Since Stephen Paget's “seed-and-soil” theory was published in 1889, a wealth of research has focused on the cascade of events involved in the spread of cancer cells from the primary tumor to secondary organs. As Paget highlighted, in addition to the intrinsic properties of metastatic cancer cells, features of the microenvironment in target organs of metastasis are also critical for successful tumor dissemination. Over the past century, metastasis research has focused predominantly on the genetic and phenotypic properties that confer the “seed” with a migratory and invasive phenotype. More recently, the contributions of cells, the extracellular matrix, and secreted factors in the metastatic microenvironment have gathered attention. In addition, although it was traditionally thought that metastasis occurred as a late event during tumor growth, there are now several lines of evidence to suggest that the onset of metastatic progression occurs early during carcinogenesis. The contributors to this book have made seminal contributions toward furthering our understanding of the molecular and cellular pathways in tumor dissemination. As outlined here, their chapters highlight the key scientific advances as well as the modern models and tools for studying metastasis.

The first four chapters focus on the state-of-the-art models and systems employed in metastasis research. In Chapter 1, Janet E. Price describes animal models of metastasis. Such in vivo approaches have distinct advantages over in vitro assays, allowing real-time study of the multistep processes of metastasis in its physiological context.