Fig. 2

Tracing the path from primary tumor to pre-metastatic niche formation: Unraveling the sequential events in metastasis development. This description outlines the evolving tumor microenvironment at various stages of cancer progression, and demonstrates key representative cell types. The primary tumor promotes the formation of the pre-metastatic niche through the release of various cells and factors. Circulating tumor cells entering the pre-metastatic niche form the tumor microenvironment of distant metastasis