Primary malignant lymphoma of the brain: demonstration of immunoglobulin gene rearrangements in four cases by the Southern blot hybridization technique

Using the Southern blot hybridization technique, four cases of the primary malignant lymphomas of the brain, histologically diffuse large cell lymphoma, were examined for the immunoglobulin gene rearrangements. In three lymphomas, the rearrangements were observed in both heavy and light chain genes, providing strong evidence for a B cell lineage of these tumors. On the other hand, in the remaining lymphoma, the rearrangement was observed only in the heavy chain gene. Despite this, immunohistochemical examination revealed positive stainings for heavy and light chain immunoglobulins in tumor cells, suggesting the occurrence of light chain gene rearrangement at the undetectable level. Thus, B lymphocytic differentiation at the gene level was demonstrated in three, or possibly all, of the primary intracerebral malignant lymphomas examined. Since no more than two rearrangements were detected in each immunoglobulin gene, these lymphomas were considered to be monoclonal in nature.