Under what circumstances would a bone marrow transplant be performed on someone with Essential Thronbocythemia? My hematology-oncologist refers to ET as blood cancer although there are no cancerous cells present. Do you agree? I have a FaceBook page if anyone cares to take a look. It's called "Living with (Primary) Essential Thrompbocythemia." I started the page over a year ago when I didn't know anyone that shared the same illness. Now we have people from 41 countries that have viewed our page.