Immunohistochemical and gene rearrangement studies of central nervous system lymphomatoid granulomatosis

Lymphomatoid granulomatosis (LYG) is a rare multisystem disorder with characteristic angiocentric lymphoproliferative features, most frequently involving the lung, skin, and rarely the CNS. LYG has been classified into three subtypes based on the relative proportions of atypical and inflammatory infiltrating cells. Most systemic LYGs have been shown to be EBV-associated, T-cell rich, B-cell proliferative disorders. Here, we present four cases of LYG arising from the CNS and have analyzed them by immunohistochemistry to assess the phenotype of the infiltrate, and by PCR-SSCP (single-strand conformation polymorphism) analysis for immunoglobulin heavy chain (IgH) and T-cell receptor (TcR) γ gene rearrangements. Three cases revealed perivascular infiltration of T-cell dominant lymphoid cells, two cases showed monoclonal TcRγ gene rearrangement, while the remaining case had a B-cell immunophenotype and monoclonal IgH gene rearrangement with EBV genome expression. This is the first report of a gene rearrangement study on CNS-LYG. We confirm that some cases of CNS-LYG are derived from T-cell monoclonal lymphoproliferative disease, although this disease should be classified as a borderline malignancy and should be separated from overt malignant lymphoma of CNS.