Primary Dural Based Marginal Zone B-Cell Lymphoma (MZBCL) is a subtype of PCNSL with an incidence rate ranging from 0.6 to 3% of all brain tumors. MZBCL typically presents as an extra-axial mass resembling meningioma.

Here we report an unusual case of MZBCL with an initial radiographic findings of mild nonspecific thickening of tentorium and pachymeningeal enhancement surrounding 7th/8th cranial nerves.

A 58-year old right-handed woman with clinical history of CMV infection, polyclonal gammopathy and unruptured left ICA aneurysm post coil embolization who presented for an evaluation of mild thickening, and enhancement of the left tentorium cerebelli and 7th/8th nerve root complex.

Differential considerations included inflammatory/autoimmune conditions (idiopathic hypertrophic pachymeningitis, neurosarcoidosis, Tolosa-Hunt syndrome), infections, structural lesion, benign or malignant neoplasm. Serum studies were normal. CSF studies were unremarkable. Flow cytometry showed no malignant cells with few small lymphocytes.

She was followed with the imaging surveillance for nine months until further increased thickening of dura on MRI. She underwent cerebellar dural biopsy that was consistent with MZBCL composed mainly of small CD20+ B-cells and negative MYD88. PET scan did not show any CNS, meningeal or systemic FDG involvement. Bone biopsy revealed no evidence of lymphoma. The focal leptomeningeal enhancement improved significantly after she received four doses of systemic rituximab treatment.