Fig. 2.

Tumor metastatic process. The metastatic process can be broken down into 5 stages. After breaching basement membrane, the primary invasive tumor cells may intravasate into either lymphatic or blood microvessels. The blood can then transport these cancer cells to distant anatomical sites, where they may be trapped and subsequently extravasate and form dormant micrometastases. Eventually some of the micrometastases may acquire the ability to colonize the tissue in which they have landed, enabling them to form a macroscopic metastasis.