Dura-associated extranodal marginal zone B cell lymphoma (MALT lymphoma)
Extranodal marginal zone B cell lymphomas of the mucosa-associated lymphoid tissue (MALT) most often originate in the stomach, but sometimes occur in other locations such as the dura mater (7). While most primary central nervous system lymphomas (PCNSLs) are high grade diffuse large B cell non-Hodgkin lymphomas, primary dural lymphomas (PDLs), a rare subtype of PCNSL, are usually extranodal MALT lymphomas and low-grade lesions (5). PDLs tend to show a female predominance, usually occur in immunocompetent hosts and have a better prognosis than other forms of PCNSL. Due to these clinicopathological features, the diagnostic work-up and the treatment strategy is entirely different from most PCNSLs. It is known that PDLs often mimic meningioma or even subdural hematoma on preoperative imaging (4, 8).
Histologically, dura-associated extranodal marginal zone B cell lymphomas (MALT lymphomas) have similar morphologic and immunohistochemical features of their counterparts in other locations (3). Usually, small mature lymphocytes invade the dura in a perivascular fashion and immunolabel with CD20 and BCL2, while they are negative for CD5, CD10, CD23, and BCL6 (3). Although not present in this case, some MALT lymphomas have rearrangements of the immunoglobulin heavy chain genes (6) or chromosomal aberrations involving the MALT1 gene. One is a translocation characteristic for gastric and pulmonary MALT lymphomas, t(11;18)(q21;q21), resulting in a API2-MALT1 fusion transcript and the other is t(14;18)(q32;q21) with IgH-MALT1 fusion, frequently seen in MALT lymphomas of the skin, salivary glands and ocular adnexa (2).
Interestingly, in a large series of dural MALT lymphoma reported by Tu et al., fluorescent in situ hybridization (FISH) performed in 12 of 15 cases failed to reveal t(14;18) or t(11;18) translocations (8).
So far, standard treatment has not yet been established. In a systematic review of the literature by Beltran et al. that included 91 patients, 70% had surgery, 73% had radiation therapy and 37% chemotherapy (1). Larger prospective studies are needed to determine optimal management.
Contributed by Marian Christoph Neidert, Henning Leske, Jan-Karl Burkhardt, Elisabeth Jane Rushing, and Oliver Bozinov