Why do they say itp is like cancer? if that makes sense

Not a tumor: Itp is when your own antibodies (immune system) attack your own platelets (the blood cells that make a clot). If you are a purist, the "i" (idiopathic) means we don't know the cause but very often we can trace it to medications, infections, autoimmune disorders like lupus, and sometimes certain malignancies like chronic leukemia. So it's not cancer but a cancer could trigger it. See?