MALT lymphoma (dura)
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MALT lymphomas of the dura (also known as extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue of the dura), are an uncommon form of CNS lymphoma, accounting for an even smaller proportion of dural masses. They are, however, the most common form of primary dural lymphoma.
Unlike other CNS lymphomas that are of large B-cell lineage, primary dural lymphomas are related to mucosa-associated lymphoid tissue (MALT), and as a result, have an indolent course and far better prognosis. On imaging, they are difficult to diagnose pre-operatively as primary dural lymphomas share many similarities with meningiomas which are vastly more frequent.
For a discussion of extracranial disease, see MALT lymphoma.
MALT lymphomas of the dura are most often encountered in middle-aged individuals, more commonly in females. They account for < 1% of all CNS lymphoma 1,2.
The presentation is usually indolent with symptoms related to mass effect, without features helpful in distinguishing them from meningiomas 1.
Unlike other primary CNS lymphomas which are usually of non-Hodgkin B-cell lineage, primary dural lymphomas tend to arise from mucosa-associated lymphoid tissue (MALT), although how and why this is the case so far remains unclear 1 (see MALT lymphoma for a general discussion).
As is the case with MALT lymphomas elsewhere, these tumors are composed of small rounded lymphocytes, marginal zone cells and plasma cells 2.
- CD5: negative
- CD10: negative B-cells
The vast majority of MALT lymphomas of the dura arise in the intracranial compartment 2.
Primary dural lymphoma shares imaging features with other small round blue cell tumors, and other dural masses. These tumors present as an extra-axial lobulated mass, that may be either solitary or multiple and are difficult to distinguish from meningiomas.
Due to high cellularity, these tumors are typically somewhat hyperdense compared to brain (as are other CNS lymphomas) 1. They generally enhance vividly.
- T1: isointense to grey matter
- vivid enhancement (usually homogeneous)
- brain tumor interface may be indistinct
- iso- to hypointense to grey matter
- edema common in adjacent brain
- DWI/ADC: restricted diffusion
Treatment and prognosis
Primary dural lymphomas are nonaggressive and patients have excellent outcomes regardless of treatment 1,2.
The differential diagnosis is essentially that of other dural masses, including:
- 1. Smith AB, Horkanyne-Szakaly I, Schroeder JW et-al. From the radiologic pathology archives: mass lesions of the dura: beyond meningioma-radiologic-pathologic correlation. Radiographics. 2014;34 (2): 295-312. doi:10.1148/rg.342130075 - Pubmed citation
- 2. Louis DN, Ohgaki H, Wiestler OD et-al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol. 2007;114 (2): 97-109. Acta Neuropathol. (full text) - doi:10.1007/s00401-007-0243-4 - Free text at pubmed - Pubmed citation