Similar to other gliomas, PXA rarely occurs in the extra-axial compartment causing primary meningeal gliomas (PMG). PMG may occur as a solitary mass or as diffuse meningeal involvement. We reviewed the relevant literature and identified only 31 cases of a solitary meningeal glial mass reported in English literature (3). Most PMG were astrocytomas (53.3%) followed by glioblastomas (30%) (3,4). To our knowledge, we are presenting the fourth case of an extra-axial PXA (Table).
Kepes originally suggested that PXAs may be derived from subpial astrocytes (2). Lehman and Giannini extrapolated to contemporary tumor stem cell theory would implicate cortical radial glial or cortical or leptomeningeal pluripotent neural progenitor cells derived from radial glia or neural crest cells in the development of PXAs
In our case, the intraoperative findings suggested an extra-axial mass arising from dura matter and lacking connection with brain parenchyma. However, the histopathological examination confirmed the diagnosis of PXA.
Typically, PXA consists of solid and cystic components on imaging. In contrast-enhanced computed tomography imaging, the cystic component is hypodense. The solid component typically appears hypo to isodense, but can occasionally be hyperdense, with areas of calcification seen in the solid component (1). However, it can be presented as a superficial mass with leptomeningeal contact (3,5). Therefore, these tumors should be considered as a differential diagnosis of intracranial meningiomas.
Due to the lack of reported data, there are no formal guidelines published on the management of PMGs. Treatment options include surgical resection followed by adjuvant therapy including radiotherapy with or without systemic therapy. In the management of parenchymal PXAs, multiple studies concluded that the importance of the extent of resection is a reliable prognostic factor for overall survivals (OS) and progression-free survival (PFS). Therefore, gross total resection (GTR) should be the goal of the surgeon (1,6). Adjuvant therapy has been generally considered minimally effective or ineffective for the treatment of PXAs. A meta-analysis of 167 patients with grade II PXA did not demonstrate an association between adjuvant therapy with improved oncologic outcomes (6). For primary meningeal PXAs, all reported cases were treated with surgery, 2 cases with subtotal resection, and 1 case with gross total resection.
The overall prognosis of PXA is relatively favorable. The OS of PXA is favorable with 5-year survival rates of >75%. However, monitoring for recurrence and malignant transformation is warranted since the recurrence rate of PXA following surgical resection is about 30% within 5 years and 40% within 10 years (7), and 10-20% undergo an anaplastic transformation (3). In his meta-analysis of 167 patients, Mallick found out that the estimated median OS was 209 months, and the estimated median PFS was 48 months (6).