How do you know those lumps are "cancer"? Can you see the cells multiplying? Maybe you have microscopic vision, but I don't; I have to rely on some profession

How do you know those lumps are "cancer"? Can you see the cells multiplying? Maybe you have microscopic vision, but I don't; I have to rely on some professional taking a sample and doing lab tests on it, and then telling me the results. To me, they're just lumps and I have no idea what I'm looking at. >This stuff was taught in high school when I was a kid You were taught in high school how to distinguish, visually, cancerous tumors from benign tumors, and you can take over as an oncologist today because of this ability? I find that hard to believe.