A condition in which cancer cells spread from the original (primary) tumor and invade lymph vessels (thin tubes that carry lymph and white blood cells through the body’s lymph system). The invaded lymph vessels then fill up with cancer cells and become blocked. Although carcinomatous lymphangitis can occur anywhere in the body, it commonly happens in the lungs. It can happen in many types of cancer but is most common in breast, lung, colon, stomach, pancreatic, and prostate cancer. Also called lymphangitic carcinomatosis.