DIAGNOSIS: Cerebral intraparenchymal myeloma
Multiple myeloma (MM) in the central nervous system (CNS), though uncommon, has been described (4,5,6,7). A completely intraparenchymal mass is rare. Our patient had prior blood and extensive soft tissue involvement at other sites. He was post autologous stem cell transplantation. Intracerebral relapse following remission after autologous stem cell transplantation has been reported (6). The unusual radiographic findings in this case, however, suggested that he had an entirely different lesion, such as a high-grade glioma. It had ring enhancement with a central nodular, septated and also enhancing area. The histology was also unusual with a trabecular arrangement of the plasmacytoid cells in a background of muco-proteinaceous material. The exact source and nature of this material are unresolved.
CNS involvement by MM usually demonstrates contiguous bone disease or meningeal relapse. Neoplastic plasma cells may be found in the cerebrospinal fluid (CSF). Presumably, the tumor spreads by a hematogenous route. Some authors report that patients with MM and CNS findings have an increased number of atypical plasma cells in the circulation (4,5,6); but the exact mechanism of CNS involvement has yet to elucidated. Some investigators feel that an extramedullary clone with high chemo-resistance is present in these patients. Other hypotheses include the presence of continuous insidious osseous disease and the expression by the myeloma of adhesion molecules such as CD11 and CD56 that allow the penetration and proliferation of the tumor cells in the CNS (6). Our case was focally positive for CD56. CD56 expression is commonly seen in myeloma; however, some reports indicate that it is even more frequently found in cases with extramedullary disease involvement (2).
In their purely extraosseus form, plasma cell neoplasms most often present as nodular or plaque-like dural masses with variable involvement of the underlying brain (1,3). They are described as soft and fleshy. Microscopically, they consist of sheets of monomorphous, monoclonal, mature CD138-positive plasma cells. The clinical presentation of CNS myeloma can be systemic with weight loss and weakness, but usually there are neurological signs as well. Headache, dysarthria, impaired mental status, memory loss, limb weakness, cranial nerve palsies, disturbances of gait and behavioral changes may occur. If the tumor is intraparenchymal, as it was in our case, the symptoms will be related to the location and size of the tumor. There have been reports of patients with obstructive hydrocephalus and hypopituitarism with diabetes insipidus (5).
In these patients the median interval from diagnosis of MM to CNS involvement is approximately 81/2 to 9 months (4,6). The treatment of CNS myeloma is variable and uncertain but has included intra-thecal therapy, cranio-spinal irradiation and systemic chemotherapy. The prognosis is bleak; the median survival from the time of diagnosis was 1.5 months (4).
Contributed by Barbara Germin, Ajay Malhotra, Vassilios Dimopoulos, Raymond Felgar