A Meningioma Mimic and Distinct Subtype of Primary Central Nervous System Lymphoma: Primary Dural Lymphoma.

Primary central nervous system lymphoma (PCNSL) is an aggressive form of extranodal non-Hodgkin lymphoma that arises in the brain parenchyma, eyes, meninges, or spinal cord in the absence of systemic disease. Primary dural lymphoma (PDL), in contrast, arises from the dura mater of the brain. PDL is usually a low-grade B-cell marginal zone lymphoma (MZL), whereas other types of PCNSL are usually high-grade large B-cell lymphoma. This specific pathological subtype has important therapeutic and prognostic implications, making PDL a distinct subtype of PCNSL. Herein, we report a case of PDL in an African American patient, in her late thirties, who presented to our emergency room with chronic headaches. An emergent magnetic resonance imaging (MRI) of the brain showed a dural-based homogeneously enhancing extra-axial mass along the left hemisphere, which was contained within the anterior and parietal dural mater. A surgical specimen was collected after an emergency debulking procedure. The flow cytometry, done on the surgical specimen obtained, was positive for CD19⁺, CD20⁺, and CD22⁺, but negative for CD5^- and CD10^-. These findings were consistent with a clonal B-lymphoproliferative disorder. The surgical pathology specimen immunohistochemistry was positive for CD20⁺ and CD45⁺, but negative for Bcl-6Cyclin D1^- and CD56^-. The Ki67 was 10-20%. These findings were consistent with extranodal MZL. Given the location and pathology, the patient was diagnosed with PDL. Due to MZL's indolent nature, location outside the blood-brain barrier, and known efficacy to bendamustine-rituximab (BR), we decided to treat our patient with BR. She completed six cycles without major complications, and her post-therapy brain MRI showed complete remission (CR). Our case adds to the sparse literature about PDL and highlights the efficacy of BR systemic chemotherapy on MZLs.