Tumor masses are composed of heterogenic subpopulations of cancer cells, and cancer stem cell theory suggests that only a specific subpopulation of these cells has the ability to sustain cancer growth and metastatic activity, whereas all of the other cancer cells have only a limited growth potential or no growth potential at all. Based on this concept in the literature, to define the aggressiveness of a tumor, examination of the molecular characteristics of metastatic cell populations is a logical way as representatives of cancer stem cells.

The poor outcome in cancer patients has mainly been attributed to local and distant lymph node metastasis as well as recurrence. The ability to assess or predict the presence of metastasis has significant prognostic relevance and treatment implications in the management of cancer. In order to decrease morbidity and mortality from cancer, it is necessary to gain a greater understanding of metastasis and define the molecular factors that contribute to this process.

We invite investigators to contribute original research articles as well as review articles that will stimulate the continuing efforts to understand metastasis and the development of strategies to early diagnose and treat these conditions. This special issue will mainly deal with general mechanism of metastasis, etiology, and treatment strategies but not with their roles in specific cancer types. However, when the article is being prepared, the topics (such as mechanism, genetics, etiology, and diagnostic as well as treatment strategies) can be discussed according to the cancer types. Potential topics include, but are not limited to:

• Molecular mechanism of metastasis
• Prognostic biomarkers and early diagnosis of metastasis
• Molecular and targeted therapeutic strategies for metastasis
• Role of SNPs, CNVs, and other polymorphisms in metastasis
• Cancer stem cell model system in metastasis
• Role of tumor and metastasis suppressor genes
• Metastasis and microenvironment
• Microarray and metastasis

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/jo/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: