WHO classification of meningiomas (adapted after Louis et al., 2016)  Meningioma WHO grade Histological type Meningothelial meningioma Fibrous meningioma Transitional meningioma WHO grade I Psammomatous meningioma Meningioma Angiomatous meningioma Microcystic meningioma Secretory meningioma Lymphoplasmacyte-rich meningioma Metaplastic meningioma WHO grade II Chordoid meningioma
Meningioma Clear cell meningioma (intracranial) Atypical meningioma WHO grade III Papillary meningioma Meningioma Rabdoid meningioma Anaplastic (malignant) meningioma Table 2.
The microscopic differential diagnosis includes chondrosarcoma, signet cell adenocarcinoma of the rectum, myxopapillary ependymoma, and chordoid meningioma
.  There are three histological variants of chordoma: classical or ("conventional") chondroid and dedifferentiated.
arising in the pineal region: a case report.
The differential diagnosis of chordoma arisen in the intracranial compartment involves chordoid meningioma
, a variant featuring chords or trabeculae of eosinophilic, vacuolated cells in a mucoid matrix background , and characterized by a high rate of recurrence following subtotal resection .
We have not considered the original meningioma a "chordoid meningioma
" based on our interpretation of the WHO classification scheme and our extensive correspondence with the members of the WHO working group (Drs.
Both of the invasive meningiomas, that is, the chordoid meningioma
and the sclerosing meningioma, are known to be aggressive variants, although currently a WHO grade has not been assigned to sclerosing meningioma.
Distinguishing chordoid meningiomas
from their histologic mimics: an immunohistochemical evaluation.
(1) Primary nasopharyngeal ESMC can often be misdiagnosed with squamous cell carcinoma nasopharynx, melanomas, lymphomas, soft tissue sarcomas, Ewing sarcoma, skeletal chondrosarcomas, chordomas, parachordomas, myoepithelial carcinoma, myxopapillary ependymomas, chordoid meningiomas
, and myxoid liposarcoma.
often contain regions that are histologically similar to chordoma, with cords or trabeculae of eosinophilic, vacuolated cells in a background of abundant mucoid matrix background.
Some of the more significant changes affecting tumor grade include classifying (1) meningiomas showing central nervous system invasion as grade II rather than grade III, (2) meningiomas with 4 or more mitotic figures per 10 high-power fields (HPFs) as grade II, (3) clear cell and chordoid meningiomas
as grade II, (4) papillary and rhabdoid meningiomas as grade III, and (5) tumors with 20 or more mitotic figures per 10 HPFs as grade III.