Findings
There is a peripherally located heterogeneous, necrotic mass in the right frontal lobe (Figure 1). There is mild associated edema and mass effect on right lateral ventricle (Figure 2 and Figure 3). Thick, irregular enhancement is seen with central necrosis (Figure 4 and Figure 5). The lesion has extended to the brain surface.
Area of similar signal intensity and nodular enhancement is seen posterior to the above mentioned lesion (white arrow in Figure 2, 3 and 4).
Scan done after one month reveals significant increase in the size of the lesions (not shown).
Diagnosis: Gliosarcoma
Gliosarcoma is a rare primary brain tumor that is composed of neoplastic glial cells mixed with a spindle cell sarcomatous element. The sarcomatous element is thought to arise from neoplastic transformation of vascular elements within the glioblastoma itself.
Gliosarcomas typically present in the sixth to seventh decade. Clinical presentation and imaging picture are indistinguishable from GBM. Like GBM, gliosarcomas are WHO Grade IV tumors.
Gliosarcomas are usually solitary, but may be multicentric. On imaging, gliosarcoma appears as a heterogeneously enhancing mass with dural invasion, and may show calvarial involvement. It is most common in the temporal lobe. FLAIR and T2-weighted images may demonstrate extensive high signal in the adjacent white matter, reflecting a combination of peritumoral edema and infiltrating tumor. Heterogeneity may be due to hemorrhage or necrosis. Enhancement is usually thick and irregular.
MR spectroscopy shows elevated choline, decreased NAA and may show lactate or lipid peak.
Perfusion images may show elevated regional cerebral blood volume beyond the area of enhancement, suggestive of tumor infiltration.
The prognosis is poor with a median survival of 6 to12 months (similar to GBM). Local recurrence is typical, with extracranial metastases being common.
