Intracranial Metaplastic Meningioma : Clinical and Radiological Characteristics of 11 Cases

Abstract

Objective Metaplastic meningioma is an extremely rare subtype of World Health Organization (WHO) grade I meningioma. It has distinctive histological subtypes according to its own mesenchymal components. Owing to its scarcity, clinical or radiological features of a metaplastic meningioma are poorly described. Methods Between 2004 and 2018, we analyzed total 1814 cases surgically proven meningioma for 15 years. Among them, metaplastic meningioma was diagnosed in 11 cases. Magnetic resonance images were taken for all patients, and computed tomography scan was taken for 10 patients. Results WHO grade I meningiomas were 1376 cases (75.9%), 354 cases (19.5%) in WHO grade II, and 84 cases (4.6%) in WHO grade III meningiomas. Metaplastic meningioma was 11 cases as 0.8% of WHO grade I meningioma and 0.6% of entire meningiomas for 15 years. Among the entire 11 metaplastic meningiomas, five tumors (45%) were diagnosed as a lipomatous subtype with rich fat components, four (36%) as an osseous subtype with extensive bone formation and two (18%) as a xanthomatous subtype. There was no cartilaginous subtype metaplastic meningioma in our study. Lipomatous and osseous metaplastic meningioma have peculiar radiological characteristics according to mesenchymal components. Conclusion We investigated a rare metaplastic meningioma subtype based on our 15-year surgical experience with meningiomas. Further investigation will be necessary for the clear clarification of tumor nature of this rare tumor.

Intraosseous metaplastic meningioma: A case report

“…Of these 15 subtypes, the 3 most common types are meningothelial, fibrous, and transitional meningiomas. In contrast, metaplastic meningioma is a rare subtype, accounting for 0.2%-1.6% of all meningiomas [1] , [2] , [3] , [4] , with a low post-surgical recurrence rate and good prognosis [5] . Metaplastic meningioma is defined as the presence of focal or widespread mesenchymal components, including osseous, cartilaginous, lipomatous, myxoid, or xanthomatous tissue, singly or in combination.…”

Related mechanisms, current treatments, and new perspectives in meningioma

“…Have vacuolated cytoplasm, intercellular microcysts, and low mitotic activity in histological appearance 23,24 Diffusely positive areas for CAIX 25 Clear cell meningioma Oval cells with clear cytoplasm, transparent vacuoles, hyalinized vascular stroma, and rare mitosis related to SMARCE1 mutations 26,27 Positive for EMA vimentin and negative for GFAP, CK7, and S-100 26,28 Papillary meningioma Is more common in younger people 21 Fibroblastic/fibrous meningioma Spindle cell neoplasms that generally lack meningothelial nests and show thick collagen bundles The nuclei of this group retain meningothelial cell characteristics, while whorls and psammoma bodies help exclude schwannoma 29…”

“…Have vacuolated cytoplasm, intercellular microcysts, and low mitotic activity in histological appearance 23,24 …”