Figure 2.

Immune and angiogenic dormancy in maintaining the cancer at a microscopic size. (A) Once the tumor undergoes immune escape and the angiogenic switch is turned on, the tumor grows locally and spreads metastases. In this model, DTCs are released at a later stage because DTCs do not gain access to the bloodstream until the tumor has acquired its own vasculature. (B) Another model stipulates that dissemination of cancer cells may occur very early in the beginning of the nascent cancer and continues throughout its growth and development. In this model, the role of immune escape is more important than the role of the angiogenic switch because microscopic tumors (and even in situ tumors) may spawn DTCs/micrometastasis before the angiogenic switch has taken place. DTCs indicate disseminated tumor cells.