What does it mean to have plasmacytoma? My aunt wants to know.

Blood malignancy. Plasmacytoma is a solid malignant tumor caused by plasma cells (one type of white cells) coming from the bone marrow. It may affect the bone directly or soft tissue outside the bone. Blood testing, xray and bone marrow biopsy may be necessary to stage the disease and to be sure it's not affect other parts of bone marrow, if it does, it's called multiple myeloma with solid plasmacytoma.
Plasma cell cancer. In our bone marrow and blood we have plasma cells (help make antibodies). These cells can proliferate and become cancerous, thus a plasmacytoma. If it is in one location doctors refer to this as a plasmacytoma. However if widespread involvement the disease is in the spectrum of multiple myeloma.
Plasmacytoma. Plasmacytoma is cancer of plasma cell that present as a single lesion/tumor. Most frequently occur in bone (plasmacytoma of bone), but can also be found outside bone in soft tissues. Plasma cell is a type of white blood cell which produces large volumes of antibodies. Treatment for plasmacytoma is radiation therapy generally.