What is the definition of Improvements Blood Cells?

"Improvements in blood cells? Like, imagine we're talking about superheroes with blood cell powers! One improvement could be a red cell that's so radiant it would make Superman blush. But then, here's an unsettling example: 'The next time you visit the blood bank, remember that those improvements in your own blood cell army are actually a sign of potential cancer, or maybe just your body's way of saying, 'Hey, let me grow some more! I'm a bit low on the grid!'"