Plasma Cell Neoplasms with Spreading in the Blood and Tissues: Extramedullary Myeloma Disease, a Rare Aggressive Form of Multiple Myeloma (First of Two Parts).

Multiple myeloma is a disease related to the proliferation of malignant plasma cells; in most patients, the disease is confined to the level of bone marrow. However, in a minority of patients, the malignant plasma cells are also localized outside the bone marrow, either at the level of peripheral blood (plasma cell leukemia) or at the level of soft tissues (extramedullary multiple myeloma). These two rare forms of aggressive MM (ultrahigh-risk (uHR) MM as MM leading to death within 24-36 months) are both associated with some molecular features and with a limited response to current treatments.