Abstract
BACKGROUND: Primary central nervous system lymphoma (PCNSL) is an aggressive extranodal subtype of nonHodgkin's lymphoma. Ventricle-predominant PCNSL, arising in the CNS ventricular system, is a rare entity. In over 90% of cases, PCNSL is classified as diffuse large B-cell lymphoma. Rarely, PCNSL may be classified as marginal zone B-cell lymphoma (MZBCL) of mucosa-associated lymphoid tissue (MALT). Taken together, a primary MALT-type MZBCL arising in a cerebral ventricle is an extremely rare presentation. CASE DESCRIPTION: A 69-year-old female presented with a persistent left frontal headache for 1 year. Magnetic resonance imaging revealed an enhancing soft-tissue lesion within the left lateral ventricle, with associated periventricular edema. We performed an excisional biopsy of the tumor, which grossly had the appearance of a meningioma. Histopathology of the tumor was consistent with MZBCL of the MALT type. The patient was treated with Rituximab and Ibrutinib. Six months after surgery, she remained neurologically intact and free of disease. CONCLUSION: We report the case of a primary MALT-type MZBCL arising in the CNS ventricular system, with characteristics mimicking meningioma. This lymphoma involved the lateral ventricle and likely originated from the choroid plexus. Meningothelial cells and epithelial cells in the choroid plexus may acquire MALT in response to chronic inflammatory stimuli, such as infection or autoimmune disease. In rare cases, MALT lymphoma may develop as part of this pathogenesis.