Morphologic and immunophenotypic characterization of primary brain lymphomas using paraffin-embedded tissue.

Primary lymphomas of the brain constitute about 1% of all primary intracranial neoplasms, but recent studies suggest an increasing incidence. Most cases are associated with an immunosuppressed state. We reviewed 29 cases of primary brain lymphoma from the Yorkshire Health Authority Region between 1970 and 1988 and found a striking increase in incidence over this period. No overt evidence of immunosuppression was found in any case. All were non-Hodgkin's in type and were classified morphologically using Kiel criteria and immunophenotypically using a panel of antibodies. Cryo-preserved tissue was available in five cases for parallel immunophenotyping. The majority of tumours were high-grade lymphomas together with three of lymphoplasmacytoid type. Thirteen tumours showed a striking pleomorphic morphology with plasmacytoid features. A reactive, predominantly perivascular monomorphic T-cell population was seen in all tumours. Most tumours were of B-cell lineage. No cases of Hodgkin's disease, T-cell or histiocytic lymphoma were present. Light chain restriction was present in only 46% of cases. The results of tumour immunophenotyping on cryostat sections were comparable with those from paraffin blocks. Our study emphasizes the value of a panel of antibodies reactive in paraffin-embedded tissue, allowing simultaneous evaluation of morphology and immunophenotype, and suitable for small biopsies received from stereotactic procedures.