People often confuse Bone Marrow Cancer and Myeloma.
It's important to understand what Myeloma is.
The white blood cells that pass through your bone marrow is called Plasma Cells, they create antibodies. Their role is to protect your bone marrow from infection.
For some unknown reason, the body produces too many white cells and the antibodies start protecting your blood from the healthy cells. In other words, it starts working against your bone marrow.
These white cells proliferate and create tumors which when located in one area, is called Plasmacytoma. When it spreads, it's called Multiple Myeloma.