Solitary Bone Plasmacytoma and Extramedullary Plasmacytoma Meletios A. Dimopoulos, MD George Hamilos, MD Address Department of Clinical Therapeutics, University of Athens School of Medicine, 227 Kifissias Avenue, Kifissia, Athens, 14561, Greece. E-mail: mdimop@med.uoa.gr Current Treatment Options in Oncology 2002, 3:255–259 Current Science Inc. ISSN 1527-2729 Copyright © 2002 by Current Science Inc. Introduction SOLITARY BONE PLASMACYTOMA Some patients with plasma cell myeloma have a single bone lesion caused by a monoclonal plasma cell infiltrate and no evidence of myeloma elsewhere. Although the exact prevalence of solitary bone plasma- cytoma (SBP) is unclear, this entity affects fewer than 5% of patients with plasma cell myeloma treated at referral centers [1••]. The diagnosis of SBP requires a biopsy of a solitary bone lesion that shows infiltration by plasma cells, normal results on a skeletal survey, absence of clonal plasma cells in a random sample of bone marrow, and no evidence of anemia, hypercal- cemia, or renal involvement that could be attributed to the plasma cell proliferative disorder. Solitary bone plasmacytoma has a lytic appearance on plain radio- graphs. Computed tomography (CT) and magnetic resonance imaging (MRI) depict the extent of SBP more clearly. The MRI is considered necessary to design the radiotherapy fields. Because MRI is more sensitive than plain radiographs in detecting occult bone lesions [2], most investigators agree that a normal MRI of the spine and pelvis should be included in the diagnostic criteria of SBP. Most patients with SBP are male; their median age is approximately 10 years younger than that of patients with multiple myeloma. SBP may involve any bone, but most often affects the axial skeleton, particularly a vertebra. Electrophoretic studies reveal a monoclonal protein in the serum or urine in 25% to 75% of patients with SBP. The levels of the protein are much lower than those with multiple myeloma. When its serum levels exceed 20 grams/L, the possibility of occult disseminated disease is high. Furthermore, a large proportion of patients with SBP do not have a monoclonal protein; the uninvolved immunoglobulins Opinion statement Solitary bone and extramedullary plasmacytomas are rare plasma cell proliferative disorders. Their diagnosis is based on histologic confirmation of monoclonal plasma cell infiltration of a single disease site and on the exclusion of systemic myeloma. For both entities, the treatment of choice is localized radiotherapy. With modern radiotherapy and with a total dose of at least 4000 cGy, the risk for local recurrence is less than 5%. There is no role for systemic chemotherapy in the management of these disorders. Approximately 30% of patients with solitary bone plasmacytoma (SBP) remain disease-free for several years; some of these patients may be cured. Patients with the best prognosis are those in whom the monoclonal protein disappears by 1 year after radiotherapy. The prognosis of patients with solitary extramedullary plasmacytoma (SEP) appears to be better than for patients with SBP because approx- imately 70% of patients with SEP remain disease-free at 10 years. With more sensitive staging procedures, the diagnosis of SBP and SEP may become less common, but the number of patients with prolonged stability and cure may increase.