- Multiple myeloma (MM) is a type of malignant blood cancer. It affects the plasma cells, which help produce antibodies and fight infection. MM is nearly always preceded by a pre-malignant state, monoclonal gammopathy of undetermined significance (MGUS) or smoldering multiple myeloma (SMM). Currently, it is not possible to predict when someone with MGUS or SMM will develop MM. Also, the disease changes in those early states are not well understood. Researchers want to look at imaging studies of people with MGUS, SMM, and MM. They will study whether the growth of blood vessels can be used to predict disease progression.