Solitary plasmacytoma of bone and soft tissues.

Between 1956 and 1978, nine patients with solitary plasmacytoma of bone (SPB) and seven with extramedullary plasmacytoma (EMP) were treated at the University of Washington Hospital and Swedish Tumor Institute. All but one patient had local radiotherapy. In the SPB group, six of nine patients progressed to multiple myeloma (MM) and five died of disease within three years after dissemination. Three of the nine patients are alive at 5, 8, and 16 years, respectively. In the EMP group, none of the seven patients progressed to MM. Five are alive 16 months to 23 years after radiotherapy. Since there are no reliable criteria for prospectively distinguishing true solitary plasmacytoma from occult MM, all patients with apparently isolated plasmacytoma should receive local radiotherapy with curative intent.