Solitary intracranial plasmacytoma.

A case of solitary intracranial plasmacytoma (SIP) spreading from the tentorium toward the right middle and posterior fossae is reported. A particular clinical finding was the presence of an abnormal IgG lambda type in both cerebrospinal fluid (CSF) and serum, which disappeared after partial removal of the tumor followed by radiation therapy. The light and electron microscopical study revealed that the tumor was composed mainly of mature plasma cells. Peculiar deposits of amyloid with a crystalloid plaque-like morphology were scattered throughout tumor tissue; also the tumor vessels showed amyloid infiltrations. The immunohistochemical study confirmed that the tumor was composed of a population of plasma cells producing a single monoclonal immunoglobulin. The findings of this case were compared to those of the few previously reported SIP.