**5. Biologic behavior**

cell types in pure or mixed form. The classical tumor cells may show elongated, irregular hyperchromatic nuclei, often with no discernible cytoplasm, and embedded in a dense fibrillary matrix, mixed with cells that display visible eosinophilic cytoplasmic processes. However,cellular diversity, such as gemistocytic cell, protoplasmic cell, sarcomatous cell, epitheliod cell, granular cell, giant cell, or small cell is eventually observed. Glioblastoma display microvascular hyperplasia

The infiltrative or diffuse forms of astrocytoma are composed of individual tumor cells that infiltrate widely throughout the brain parenchyma with a cellular density and degree of anaplasia that increase with tumor grade. They are characterized by invasive growth such that nonneoplastic cells are often intermixed and may even predominate in some areas. The secondary structures of Scherer include subpial condensation, perineuronal satellitosis, and perivascular aggregation. The extreme end of the infiltrative spectrum, previously assigned as gliomatosis cerebri; it involves multiples lobes of the brain, often bilaterally and frequently

**Figure 2.** Histopathology. (A) Diffuse astrocytoma. Tumor cells show elongated, irregular hyperchromatic nuclei, with no discernible cytoplasm and embedded in a dense fibrillary matrix, mixed with cells that display visible eosinophilic cytoplasmic processes. (B) Glioblastoma displays a hypercellular-solid neoplasm with fuzzy or ill-defined margins, with diffuse parenchymal infiltration. (C) Glioblastoma: a pseudopalisading necrosis area. (D) Glioblastoma: an epitheliod-like cell area. (E) Glioblastoma: hypercellularity, tumor cells show elongated, irregular hyperchromatic nuclei, with no discernible cytoplasm and embedded in a dense fibrillary matrix, mixed with cells that display visible eosinophilic cytoplasmic processes. (F and G) Glioblastoma: cooption blood vessels surrounded by tumor gemistocytic cells. (H) Glioblastoma

displaying microvascular hyperplasia. (I) Giant-cell glioblastoma corresponding to **Figure 1C**.

and tumor necrosis (pseudopalisading areas or infarct-like areas) [11, 12] (**Figure 2**).

16 Glioma - Contemporary Diagnostic and Therapeutic Approaches

extending into the brain stem, cerebellum, and even the spinal cord [11, 12].

Today, gliomas still represent a serious and discouraging brain tumor; despite the diversity of treatment modalities, generally, the prognosis for patients is still poor (i.e., fatality and sequelae). Even with surgical resection and aggressive treatment with chemotherapy and radiotherapy, the prognosis for patients with astrocytomas remains very poor [15].
