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Primary extranodal marginal zone B‐cell lymphoma of the mucosa‐associated lymphoid tissue type in the CNS

Extranodal marginal zone B‐cell lymphoma of the mucosa‐associated lymphoid tissue (MALT) type has been reported in various internal organs. Here a case is reported of MALT lymphoma developing in the cerebellopontine (CP) angle in a patient with Sjögren syndrome, and the concept of MALT lymphoma of the CNS is introduced. Pathologically, the tumor showed inflammatory features of reactive lymphocytic infiltration with follicle formation, but there were slightly atypical lymphocytes and plasmacytes with B‐cell markers. These cells invaded reactive follicles, showing follicular colonization, and showed aberrant expression indicating their neoplastic nature. A review of the literature revealed eight cases of MALT lymphoma originating from the dura mater and one from the CP angle. The average age of patients was 50 years (range 28–66 years), and all patients were female. The tumors were slow to develop and the patients were cured after surgical removal and/or additional therapies. It is proposed that MALT lymphoma should be considered as a differential diagnosis of inflammatory pseudotumor of the CNS.