Stereotactic biopsy diagnosis of primary non-Hodgkin's lymphoma of the central nervous system. A histological and immunohistochemical study.

We report 29 cases of primary non-Hodgkin lymphomas (NHL) of the Central Nervous System (CNS), 26 of which were diagnosed by stereotactic biopsy and 3 by autopsy. In seven cases the patients were affected by AIDS. Histological examination of this series revealed 15 cases of immunoblastic lymphoma, 12 cases of centroblastic lymphoma, 1 case of lymphoplasmacytic immunocytoma and 1 case of unclassified high grade lymphoma. By immunohistochemistry the B-cell origin of lymphoma cells was demonstrated in 28/29 cases. Eight cases were assigned to the B-cell lineage by demonstration of monotypic surface or cytoplasmic immunoglobulin or of the B-cell phenotype CD22+, CD2-, CD3-, CD5-. In twenty cases the B-cell nature of lymphoma was identified by positivity with two or more anti-B monoclonal antibodies (LN1LN2MB2) and negativity by the anti-T monoclonal antibody UCHL1. The histologically unclassified case was a peripheral T-NHL (CD1-, CD2+, CD3-, CD5+, CD22-). We conclude that histological and immunohistological evaluation of stereotactic biopsy specimens provides sufficient information for diagnosis and phenotypic characterization of primary NHL of the CNS. These lymphomas exhibit important predominance of high-grade malignancy histological types and are nearly always B-cell derived. In addition, we provide further evidence that the panel of monoclonal antibodies LN1, LN2, MB2, and UCHL1 is useful for immunophenotypic characterization of brain lymphomas when only paraffin embedded stereotactic biopsy tissue is available.