my understanding is that the word "concentrated" does a lot of heavy lifting, and modern thought is that most cancers started spreading cells all over the body, even at very early stages.
metastatic cancer is a numbers game. for example. at stage 0-1, you might still have millions of cancer cells throughout your body, and there is a good chance your immune system can clean them up. At stages 2 or 3 there might be trillions of non-local cancer cells, with a proportionally greater chance of propagation.
metastatic cancer is a numbers game. for example. at stage 0-1, you might still have millions of cancer cells throughout your body, and there is a good chance your immune system can clean them up. At stages 2 or 3 there might be trillions of non-local cancer cells, with a proportionally greater chance of propagation.