When a pathologist examines tissue removed during a lumpectomy or mastectomy, one of the things she looks to see is whether cancer cells are present in any of the blood vessels or lymphatic vessels. If they are, it is referred to as vascular invasion, lymphatic invasion, or lymphovascular invasion (LVI). A woman can have lymphovascular invasion but not have positive lymph nodes. This could be because the invasion hasn’t spread to the lymph nodes or because it has bypassed the nodes and moved on to other areas of the body. When LVI is present, doctors assume this means the cancer has acquired the genetic mutation it needs to create its own blood vessels, a process called angiogenesis. Because a tumor that has the ability to create its own blood vessels may have already begun to spread cancer cells to other parts of the body, the presence of LVI is an indicator that treatment should most likely include chemotherapy or hormone therapy (if the tumor is hormone sensitive).