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 .
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 .
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 .
- typically isointense to grey matter (same as typical grade 1 meningiomas)
- 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 .
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
- typically arising in the midline from the clivus
- almost invariably associated with bony destruction
- typically arising from the central base of the skull, near the petroclival synchondrosis
- may have chondroid ossification (rings and arcs)
- myxoid soft-tissue tumors