The differential diagnoses base on clinical history included malignant meningioma and metastatic breast carcinoma. The histologic findings of biphasic patterns, with areas displaying high grade astrocytic and unequivocal areas of mesenchymal differentiation with a reticulin network but without GFAP immunoreactivity were diagnostic of gliosarcoma. The findings of rare EMA immunoreactivity and negative cytokeratin immunoreactivity were helpful to exclude malignant meningioma and metastatic breast carcinoma.
Gliosarcomas comprise approximately 2% of all high grade gliomas (2, 11) and are characterized by a biphasic tissue pattern, with areas displaying definitive glial and mesenchymal differentiation (1, 7). The term gliosarcoma was described in 1898 by Stroebe (13). In 1958, Feigin et al defined gliosarcoma as a glioblastoma subtype and the term "Feigin tumor" denotes gliosarcomas in which proliferating vessels had acquired the features of sarcoma (3). Some studies showed expression of monohistiocytic markers, indicating that gliosarcomas develop from histiocytes whereas others suggested an origin from fibroblasts, pluripotent mesenchymal cells of the perivascular adventitia or perivascular spaces (5, 8). More recent publications suggested a common origin of for the two components; the sarcomatous areas result from advanced glioma progression with acquisition of a mesenchymal phenotype (6, 10). This idea is strongly supported by many investigators. Reis et al. showed that gliosarcomas exhibit clinical features and a genetic profile similar to primary (de novo) glioblastoma, i.e. advanced patient age, short clinical history, and frequent p16 deletions and PTEN mutations (12). The presence of identical genetic alterations in both gliomatous and sarcomatous components strongly supports the concept of monoclonal origins of gliosarcomas.
It has been suggested that gliosarcomas carry a somewhat more favorable prognosis (12) than glioblastoma multiforme but large clinical trials have not succeeded in revealing a significant difference in outcome (4, 11).
Contributed by Paisit Paueksakon, MD, Jerry B Blacklock, MD, Suzanne Z Powell, MD, J Clay Goodman, MD