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Study the differences between the structure of blood capillaries and lymphatic capillaries, and then come up with a hypothesis as to why metastasis starts in the lymphatic system more often than not. As metastasizing cells flow through the lymphatic system, they drain into the subclavian veins. Then they move into the heart to be recirculated by the arteries and find there way into blood capillaries. Thinking about blood circulation and metastasis, explain why metastatic tumors would most often end up in the lungs, brain, and liver? Lastly, use your knowledge of metastasis to explain why cancers most often come back after remission as metastatic tumors in distant locations from the original tumor?