Gliosarcoma - a glioblastoma multiforme variant

Clinical History

A 79-year-old man came to the Emergency Department complaining of acute left-side hemiparesis and sensory disturbance of the homo-lateral side of the body. Neuroimaging study was performed.

Imaging Findings

MR study demonstrates an intra-axial right temporal tumour with two distinct components: one solid, hyperintense on T2- weighted images, enhancing after intra-venous Gadolinium administration without diffusion restriction; the other cystic, also hyperintense on T2-weighted images, showing a thin peripheral enhancement of its walls.
Proton MR spectroscopy demonstrates an elevated choline peak, reduced NAA peak and elevation of Cho/Cr e Cho/NAA ratios. These markers changes suggest cellular proliferation, as happens in tumours.
rCBV map shows an important increase of relative cerebral blood volume of the solid component of the lesion. This kind of increase has been related to proliferative tumour activity and high WHO classification grades.
Overall, this study exhibits an intra-axial temporal tumour with markers of cellular proliferation and high grade lesion.

Discussion

Primary gliosarcoma (PGS) is, according to the 2007 World Health Organization Classification of Tumors of the Central Nervous System, a grade IV neoplasm and a variant of glioblastoma multiforme (GBM). It is characterised by a biphasic tissue pattern with alternating areas displaying glial and mesenchymal differentiation. Gliosarcoma was originally defined as a glioblastoma in which the sarcomatous component was the consequence of malignant transformation of proliferating tumour vessels, however, there is cytogenetic and molecular evidence for a monoclonal origin of both the glial and mesenchymal components.[1]
The incidence of gliosarcoma is between 1% and 8% of all malignant gliomas and thus represents an exceptionally rare neoplasm.[2] They usually affect patients in the sixth to seventh decade of life with a male preponderance.[3] Histologically, the glial component fulfills the cytologic criteria of GBM, and the mesenchymal component may show a wide variety of morphologies with origins from fibroblastic, cartilaginous, osseous, smooth and striated muscle, or adipose cell lineage. [4]
Most gliosarcomas are de novo, and are hence termed primary gliosarcomas, whereas those detected at subsequent surgery for previously resected and irradiated GBMs are termed secondary gliosarcomas.[5] Gliosarcoma has a higher potential to metastasise than GBM. Extracranial metastases include the visceral organs and the spinal cord, the latter being extremely rare.[6]
Gliosarcomas are peripherally located and involve the temporal, parietal and occipital lobes.[7] A modest temporal lobe predilection was observed.[2]
On MR they have inhomogeneous or cystic appearance with surrounded vasogenic oedema. They are intra-axial but abutting a dural surface with intense heterogeneous tumour enhancement. On T2-weighted images they usually have intermediate signal intensity with peripheral high-signal intensity due to the surrounding oedema. Haemorrhage and necrosis are common. Gliosarcoma should be included in the differential diagnosis of any tumour that appears to be intra- axial but abuts a dural surface and shows imaging characteristics similar to gray matter on T2-weighted images.[7]
The current classification of PGS as a variant of GBM reflects the fact that they are often treated in the same manner,[4] with modalities including tumour resection, postoperative radiation therapy, and chemotherapy.[5]
Survival analyses show that gliosarcoma survival is at least as dismal as that observed with GBM. The median survival among all gliosarcoma patients is 9 months.[2]

Differential Diagnosis List

Final Diagnosis

Primary gliosarcoma

URL:	https://www.eurorad.org/case/9114
DOI:	10.1594/EURORAD/CASE.9114
ISSN:	1563-4086