An 80 year old asymptomatic woman on a routine examination was detected to have a monoclonal spike on serum electrophoresis (IgG levels 1.5 g/dl). Bone marrow revealed plasma cells of 8%. Which of the following represents the most likely diagnosis?
Multiple myeloma Indolent myeloma Monoclonal gammopathy of unknown significance Waldenstorm's macroglobulinemia