Development of stroma in malignant lymphomas of the brain compared with epidural lymphomas. An immunohistochemical study.

The relation of lymphoma cells to gliomesenchymal stroma within nervous tissue was studied by peroxidase-antiperoxidase immunostaining of formalin-fixed and paraffin-embedded surgical specimens for fibronectin (FN), factor VIII-related antigen and glial fibrillary acidic protein in 17 malignant non-Hodgkin lymphomas of the brain. For comparison, 9 non-Hodgkin lymphomas, 6 Hodgkin lymphomas, and 19 plasmacytomas of the spinal or cranial epidural spaces were studied with the same methods. Lymphoma cells were consistently negative for all markers. All lymphomas of the brain showed conspicuous concentric perivascular circles of immunoreactivity for FN in parts infiltrating brain tissue. Such structures are considered to derive from splitting of basal laminae of preexisting brain vessels; they were not seen in tumors of the epidural space. Cells with conspicuous FN content were found in brain as well as in epidural lymphomas. A monohistiocytic origin of those cells was confirmed by presence of monohistiocytic markers lysozyme and alpha-1-anti-chymotrypsin. Thus, additional immunostaining for FN seems to be useful for detecting monohistiocytes/macrophages in brain tumors.