http://youtu.be/OcigJn8UJNQ View full lesson: http://ed.ted.com/lessons/how-does-cancer-spread-through-the-body-ivan-seah-yu-jun Cancer usually begins with one tumor in a specific area of the body. But if the tumor is not removed, cancer has the ability to spread to nearby organs as well as places far away from the origin, like the brain. How does cancer move to these new areas and why are some organs more likely to get infected than others? Ivan Seah Yu Jun explains the three common routes of metastasis. Lesson by Ivan Seah Yu Jun, animation by Andrew Foerster.