lipomatous meningioma

Lipomatous meningiomas are rare histological variants of meningiomas, accounting for only 0.3% of all meningiomas .

Although reported numbers are too small to confirm that this is definitely the case, they appear to share similar epidemiology, clinical presentation and treatment and prognosis as other meningiomas, and thus these features are not repeated here.

Pathology

Lipomatous meningiomas are currently (WHO 2007 classification) considered a type metaplastic meningiomas, and demonstrate tumor cells which have appearances mature adipose tissue, there is evidence that in fact they represent accumulation of lipids within meningothelial cells rather than true metaplasia into adipose tissue .

Radiographic features 

Radiographic features depend on the amount of fat present within these tumors. When the amount of fat is small, these tumors are indistinguishable on conventional imaging from the more common conventional types of meningioma, and thus this is not repeated here.

When fat is abundant, then they deviate from the normal appearance in line with the presence of fat.

CT

Lipid rich lipomatous meningiomas are of lower density than conventional meningiomas (which are usually isodense or slightly hyperdense to brain parenchyma). In such cases they have density measurements as low as -50 to -100HU . Such low density tumors do however usually have some enhancing components and share some of the morphological features of meningiomas (e.g. dural tail)

MRI

Lipomatous meningiomas with abundant fat will have fat like signal:

• T1: hyperintense
• T2: hyperintense
• Fat saturated sequences: will demonstrate signal loss
• T1 C+: heterogeneous enhancement

Differential diagnosis

Lipomatous meningiomas with little lipid accumulation will be indistinguishable from typical meningiomas and thus share their differential diagnosis. On the other hand lipomatous meningiomas with abundant fatty material will have a very different differential diagnosis consisting of:

• intracranial lipoma
  • homogeneous fat
  • no enhancement
  • located within the subarachnoid space, often in basal cisterns or in a pericallosal location
• intracranial dermoid cyst
  • can rupture with subarachnoid droplets of fat
  • no solid enhancing component (if present consider mature teratoma)
• xanthomatous meningioma
  • indistinguishable (?)
• osseous meningioma
  • fat signal / density will be confined to the 'medullary cavity' of ossification (thus abundant peripheral calcification)
• intra-axial tumors (rarely can have fatty metaplasia / signal intensity) 
  • glioblastoma (GBM)
  • pleomorphic xanthoastrocytoma (PXA)
  • metastatic mucinous carcinoma

Siehe auch:

• Meningeom
• Balkenlipom
• zerebellopontines Lipom (Lipom im Kleinhirnbrueckenwinkel)
• metaplastic meningioma

und weiter:

• intrakranielle Lipome