Lymphoplasmacyte-rich meningiomas are rare histological variants of meningiomas, characterised by prominent lymphoplasmacytic infiltrates into the tumour, sometimes rendering the underlying meningothelial component inconspicuous.
They also have an unusual clinical course (for meningiomas) which instead mimics an inflammatory process 1. Although reported numbers are few, and thus the features of these tumours have not been firmly established, they appear to differ from conventional meningiomas in a number of ways.
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Epidemiology
Unlike the usual meningiomas, lymphoplasmacyte-rich meningiomas are encountered more frequently in somewhat younger patients, without an obvious gender predilection 1.
Clinical presentation
Although the presenting symptom is similar to other intracranial masses (headache - most common, hemiparesis, seizure, dizziness, visual deficits), the course is more acute mimicking an intracranial inflammatory disease. Peripheral blood abnormalities are also detectable, including anaemia and polyclonal gammopathy, which normalise following resection 2,4.
Pathology
Although considered a variant of meningioma, the exact pathogenesis remains unclear, and whether lymphoplasmacyte-rich meningiomas arise as tumours or inflammatory masses remains to be elucidated 2. In any case, these masses are characterised by meningothelial tumour cells (appearing similar/identical to a typical meningothelial meningioma) with abundant infiltrating lymphocytes and plasma cells 1,3. Importantly, and supporting the contention that these are actually meningiomas with inflammatory infiltrates is that the inflammatory cells are not monoclonal/neoplastic 3.
Radiographic features
Due to the relatively few cases reported it is difficult to make dogmatic statements about the imaging features of these tumours.
In many instances they are solitary, resembling other variants of meningioma, but multiple masses have been reported, including involving the spine 4. They can have extensive relatively flat growth, similar to en plaque meningioma, and may have indistinct margins and vasogenic oedema in the adjacent brain parenchyma 5.
Differential diagnosis
The differential diagnosis for this rare entity includes:
other histological variants of meningioma
hypertrophic pachymeningitis e.g. tuberculous pachymeningitis
intracranial involvement with Erdheim Chester disease