General
- MALT lymphoma of the dura is classified as a miscellaneous rare lymphoma in the Central Nervous System (CNS).
- It is a dural-based lymphoma composed of tumour cells having morphological characteristics of marginal zone B cells with small or medium-sized nuclei and pale cytoplasm.
- Lymphomas primary in the dura mater are much less frequent than those primary in the brain
- This type of lymphoma shares histological and immunohistological features with extraneural MALT lymphomas.
- Most common dural lymphoma is MALT lymphoma
- Exceedingly rare cases of MALT lymphoma arising in the brain have also been reported
Definition
- Essential:
- A dural-based lymphoma composed of tumour cells with morphological characteristics of marginal zone B cells with small or medium-sized nuclei and pale cytoplasm.
- Immunohistochemical expression of B-cell markers (CD20, CD79a) with demonstration of meshworks of CD21+, CD23+, CD35+ follicular dendritic cells.
- Desirable:
- FISH analysis for trisomies and MALT lymphoma-associated translocations.
- Gene rearrangement studies to document clonality, if not already proved by immunophenotyping.
WHO Grade
- The tumour is categorized as a low-grade B-cell lymphoma.
- It does not have a defined numerical CNS WHO grade (1–4) specified in the sources.
Localisation
- Cranial dura
Numbers
- Male-to-female ratio of approximately 1:5
- Patients are almost exclusively adults.
Histopathology Features
Macroscopic Features
- It manifests as a solitary mass or plaque-like thickening of the dura.
- The mass often mimics a meningioma.
Microscopic Features
- It is composed of small lymphocytes and marginal zone cells, often showing plasmacytic differentiation.
- A subset of cases features tumour cells with abundant clear cytoplasm (monocytoid morphology).
- Occasionally, associated amyloid deposition is seen.
- The lymphoma may arise in association with meningothelium, sometimes containing entrapped meningothelial cells.
- Infiltration into the subjacent brain parenchyma and Virchow-Robin spaces occurs infrequently.
Immunophenotype
- Neoplastic B cells are typically positive for B-cell markers CD20 and CD79a.
- They are typically negative for CD5, CD10, CD23, and BCL6, but positive for BCL2.
- Clonal plasma cells, often IgG4+, are frequently observed.
- The proliferation index (Ki-67) is characteristically low.
Pathogenesis
- The tumour may be etiologically linked to chronic inflammation (of infectious or autoimmune origin), similar to non-CNS MALT lymphoma.
- Molecular alterations can include trisomies, most often of chromosome 3.
- In cases exhibiting monocytoid morphology, activating $NOTCH2$ mutations along with inactivating $TBL1XR1$ mutations are common.
- Clonal rearrangement of IG genes has been reported.
Clinical Features
- Symptoms are variable, often presenting as a slow-growing mass.
- Headache
- Seizures
- Dizziness
- Focal neurological defects
- Visual changes
- If spinal dura → spinal cord compression
- The lesion may be mistaken for a meningioma.
Radiological Features
- It typically appears as a solitary mass or plaque-like thickening of the dura.
- The mass clinically and radiologically mimics a meningioma.
Management
- Management usually involves resection, radiation, and/or chemotherapy.
- It exhibits a good outcome following local treatment.
- Clinical staging is recommended to exclude any systemic manifestations.
Prognosis
- The prognosis is very good.
- Patients typically achieve complete remission.
- Local and systemic relapses are rare.
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