Okay kiddo, let's talk about something called reed-sternberg cells. In our body, we have something called lymph nodes which help us fight off illnesses. But sometimes, these lymph nodes get sick themselves and start to grow in the wrong way.
Now, imagine these sick lymph nodes like a garden that has some bad plants that need to be taken out. But instead of taking out the bad plants, our body tries to fix them by sending in some guys called immune cells.
But here's the catch - there's a special type of sick plant that these immune cells can't take out. It's called the reed-sternberg cell. These cells are like the worst kind of weeds that keep growing out of control and refuse to die.
These cells are really bad news, because they keep the garden sick and can turn into something called Hodgkin's lymphoma. This is a type of cancer in the body that can make someone very sick.
So doctors need to keep an eye out for these reed-sternberg cells and make sure they don't cause any big problems. They might give people medicine or surgery to help their garden get rid of these bad weeds and become healthy again.