chordoid meningioma

Chordoid meningiomas are uncommon histological variants of meningiomas, and due to their predilection for rapid growth and local recurrence are designated as grade 2 tumors under the current WHO classification of CNS tumors.

Chordoid tumors are encountered in a very wide age range (possibly somewhat younger than other meningiomas ), in a wide range of locations within the intracranial cavity and have clinical presentations indistinguishable from other meningiomas . These are therefore discussed in the main meningioma article.

An association with Castleman disease was part of the original description but is only uncommonly encountered .

Pathology

Chordoid meningiomas have characteristic histological appearances, which contribute to their distinctive diffusion characteristics on imaging (see below).

The epithelioid tumor cells demonstrate cytoplasmic vacuolization and are embedded in a mucoid matrix which has abundant hyaluronic acid and chondroitin sulfate.

The mitotic index of these tumors has been variably reported (0.4-11.4%) and it is likely that this is not the underlying cause of higher reported recurrence rate .

Chordoid tumors are usually vimentin EMA positive, and GFAP negative .

Radiographic features

MRI

T1 and T2 signal characteristics are generally similar to other meningiomas, and no morphological features are particularly helpful in distinguishing chordoid meningiomas from other variants . Generally, they are probably more heterogeneous and perhaps more likely to involve adjacent bone, however, limited numbers in reported series make this difficult to assess .

• T1
  • typically isointense to grey matter (same as typical grade 1 meningiomas)
• T2 
  • typically mildly hyperintense to grey matter (grade 1 tumors are typically isointense)
  • peritumoral edema is variable (absent to pronounced)
• T1 C+
  • most a vividly enhancing
  • occasional areas of non-enhancement due to necrosis are identified

The most helpful MRI feature in distinguishing a chordoid meningiomas from other histological variants are their diffusion characteristics. They typically have facilitated diffusion with a mean ADC value of 1620 +/- 0.33 x 10 mm/s according to one study . In contrast, WHO grade 1 meningiomas, non-chordoid grade 2 tumors and grade 3 tumors all have more pronounced diffusion restriction, similar or lower to brain parenchyma (~800 x 10 mm/s).

Treatment and prognosis

Chordoid meningiomas are treated with surgical excision and if complete resection is accomplished then a cure is possible. In subtotal resection (Simpson grade 4) or in cases of recurrence, radiotherapy is also often used .

They are, however, considered WHO grade 2 tumors on account of a higher rate of local recurrence (up to 42%) .

History and etymology

Chordoid meningiomas were first described in 1980 (single case report in a 15-year old) and subsequently named 1988 .

Differential diagnosis

In addition to all other histological variants of meningiomas (especially microcystic subtype), chordoid meningiomas need to be distinguished from other extra-axial tumors with an abundant extracellular matrix. Therefore the differential includes:

• microcystic meningioma
  • typically demonstrate brighter T2 signal
  • less facilitated diffusion
• chordoma
  • typically arising in the midline from the clivus
  • almost invariably associated with bony destruction
• chondrosarcoma
  • typically arising from the central base of the skull, near the petroclival synchondrosis
  • may have chondroid ossification (rings and arcs) 
• myxoid soft-tissue tumors

Siehe auch:

• Meningeom