Primary low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arising in dura.

We report 2 cases of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type presenting as primary lesions in the intracranial dura. Both patients are female, and, prior to biopsy were felt to have subdural hematoma and meningioma based on preoperative MRI scans. Histologically, both cases showed a diffuse proliferation of small centrocyte-like cells or monocytoid B cells admixed with a moderate number of large transformed cells. Reactive germinal center formation was present, as was plasmacytoid differentiation in one case. These histologic features are identical to those associated with low-grade MALT lymphomas arising at other more typical sites. Clinically, both patients were found to have stage IE disease at diagnosis without evidence of lymphoma outside of the central nervous system. Immunophenotypically, the lymphomas expressed B-cell-associated antigens CD20 and CD79a without coexpression of CD5, CD10, or CD23, and 1 of the 2 cases tested showed monoclonal rearrangement of the immunoglobulin heavy chain gene without rearrangement of bcl-1 or bcl-2. MALT lymphomas have recently been described in the dura and are postulated to arise in association with meningoepithelial cells. It is important that this entity be recognized and distinguished from other small B-cell non-Hodgkin's lymphomas such as mantle cell lymphoma, small lymphocytic lymphoma, or follicular small cleaved cell lymphomas, since localized low grade MALT lymphomas are usually clinically indolent proliferations which may require only minimally aggressive therapy.