Case Report: Extranodal marginal zone B-cell lymphoma in the lateral ventricle: literature review.

Primary central nervous system (CNS) mucosa-associated lymphoid tissue (MALT) lymphoma is a rare, low-grade B-cell lymphoma that typically arises in the dura, and its occurrence within the ventricular system is exceedingly rare. We report a case of primary CNS MALT lymphoma located in the right lateral ventricle of a 62-year-old man. The patient underwent gross total resection, followed by postoperative treatment with ifosfamide combined with a Bruton's tyrosine kinase (BTK) inhibitor, and adjuvant radiotherapy. At the latest follow-up, no evidence of recurrence was observed. A review of the literature revealed only eight previously reported cases of ventricular MALT lymphoma, many of which were initially misdiagnosed on imaging as meningioma, metastasis, or ependymoma. Although chronic inflammation has been implicated in MALT lymphomas outside the CNS, potential infectious or inflammatory triggers in ventricular MALT lymphoma remain unclear. This case expands the recognized anatomical spectrum of CNS MALT lymphoma and proposes a hypothesis that lateral ventricular tumors may originate from the pia mater folds of the choroid plexus, highlighting the need to consider MALT lymphoma in the differential diagnosis of intraventricular lesions.