The tumor microenvironment: biology of a complex cellular and tissue society.

The tumor microenvironment is a "complex society" of many cell types and their extracellular matrix. All these cell types and the matrix take part to the generation of a tumor "tissue". It is well established that preneoplastic proliferating cells cannot give origin to a tumor without an appropriate blood supply. In fact, angiogenesis could be considered the rate limiting step of tumor growth. In this context microenvironment components play a pivotal role in the regulation of the angiogenic switch and in cancer progression. For these reasons the comprehension of biological and molecular mechanisms involved in the relationship between tumor cells and the microenvironment could unveil new therapeutic and preventive approaches to cancer. In this complex scenario molecular imaging of the microenvironment is crucial to dissect cellular and stromal dynamic contributions.