An immunohistological study of immunoglobulin content of primary central nervous system lymphomas.

Paraffin sections of surgical and autopsy material from 24 cases of primary CNS lymphoma were examined for the presence of cytoplasmic immunoglobulin by an immunoperoxidase technique. Definite staining for cytoplasmic immunoglobulin was observed in 13 cases, and in eight of these the pattern of staining was consistent with current concepts of monoclonality. In every case the histological diagnosis of malignant lymphoma was confirmed, and cases were subclassified by both the Lukes-Collins and the Rappaport classifications. Morphologically 12 of the 24 cases resembled immunoblastic sarcoma occurring outside the CNS. Other cases showed features of follicular center cell lymphoma or plasmacytoid lymphocytic lymphoma. Of those cases with positive immunoglobulin staining of tumor cells, the majority showed some plasmacytoid features. It was concluded that the primary CNS lymphomas resemble their counterparts occurring outside the CNS, and that at least a proportion are derived from the B lymphocyte.