IndexIntroduction to gliomasThe histopathology of gliomasMicroscopic recognition of diffusely infiltrating gliomasMorphological typing of diffusely infiltrating gliomasGrading of diffusely infiltrating gliomasCentral nervous system (CNS) tumors constitute 1–2% of all neoplasms. However, central nervous system neoplasms probably have the most varied manifestations of all tumor sites. There are several anatomical subregions in the craniospinal axis, and each of these has a predilection for a particular tumor subtype. Furthermore, each tumor can be divided into prognostic groups based on the extent of surgical resection, performance status, imaging findings, grade, age, and molecular characteristics. Among neoplasms of the central nervous system, gliomas are the most common tumors. The incidence of CNS tumors in India varies from 5 to 10 per 100,000 inhabitants with an increasing trend and represents 2% of neoplasms. Astrocytomas (38.7%) were the most common primary tumors, and the majority were high-grade gliomas (59.5%). Even more interestingly during the presentation it was observed that the average age of glial tumors was at least a decade earlier than that reported in the Western population, which could be partially explained by the lower life expectancy and a higher percentage of the population youngest in India2. Diffusely infiltrating gliomas (IGs) are a diverse set of primary central nervous system neoplasms characterized by tumor cells that perniciously invade the surrounding central nervous system parenchyma from which they originate. Compared to tumors arising in other organs, one of the unique characteristics of IG is that no neoplastic precursor lesions have been described. That is, by the time they are declared to the patient, the attending physician or the pathologist's microscope, GIs are already expected to progress. Precursor dysplastic lesions or in situ neoplastic entities that have not yet become invasive, that can be cured with surgical excision, and that do not in themselves pose a fatal threat to the patient, are outside the IG spectrum. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Infiltrating gliomas, when discussed from a histologic and historical framework, consist of 2 broad classes of tumors, originally designated based on their morphologic characteristics alone that resemble 2 types of non-neoplastic glial cells: oligodendrogliomas and astrocytomas infiltrators. The latter group excludes noninfiltrating astrocytomas, such as pilocytic astrocytoma, subependymal giant cell astrocytoma, and pleomorphic xanthoastrocytoma3. The clinical and histopathological profile of these tumors ranges from indolent to highly anaplastic and rapidly growing. The rapid growth of these lesions requires neoangiogenesis, which in turn depends on vascular endothelial growth factor (VEGF), which has been shown to be an important inducer of brain tumor angiogenesis. Furthermore, cyclooxygenase 2 (COX-2) may be involved in the regulation of angiogenesis by modulating VEGF. With multidimensional molecular datasets spanning ever-larger numbers of patients with infiltrating gliomas, our understanding of the disease at the time of surgical resection has improved dramatically, and this understanding is even more important. reflected in the updated WHO classification. However, despite all these advances, the prognosis of gliomas remains poor. Therefore, it is timely and necessary to analyze the value of new immunohistochemical markers for classification andpossible prognosis of diffusely infiltrating gliomas. Introduction to GliomasGliomas are a large group of genetically and pathologically diverse neoplasms that tend to grow into the surrounding brain parenchyma in a diffuse infiltrative manner. Tumor cells tend to invade white matter tracts, perivascular spaces, subpial regions, and surrounding neurons (known as the perineuronal process).satellitosis). The term glioma includes astrocytoma, glioblastoma, ependymoma, and oligodendroglioma as well as their various subtypes and combinations. As a general rule, gliomas tend to contain glial fibrillary astrocytic protein (GFAP) and lack reticulin, collagen, and fibronectin which distinguish them from nonglial neoplasms. Neoplastic glial cells in the central nervous system parenchyma may also be difficult to distinguish from gliosis. Glioma cells tend to be pleomorphic with nuclear atypia, mitosis, and calcifications. Gliomas expand while gliosis contracts. Granular calcifications scattered among hypercellular glia favor a glioma over gliosis. Cell density in gliosis tends to be relatively uniform, whereas some gliomas tend to show a nonuniform distribution of neoplastic cells. Another feature is nuclear spacing: glioma nuclei frequently touch and may even indent each other while normal glial nuclei or those in the gliotic parenchyma do not. The histopathology of gliomas Microscopic recognition of diffusely infiltrative gliomas Histopathological diagnosis is the gold standard for the classification of gliomas. An adequate microscopic diagnosis provides important prognostic information and forms the basis for further patient management. Most gliomas are characterized by diffuse infiltrative growth of tumor cells in the pre-existing parenchyma of the central nervous system and can be typed based on their histopathological features as astrocytic, oligodendroglial, or oligoastrocytic tumors. Furthermore, these gliomas are assigned a degree of malignancy based on the presence of esp. the following characteristics: nuclear atypia, mitotic activity, florid microvascular proliferation and necrosis. It is important to rule out other diagnoses before arriving at a diagnosis of diffuse glioma. Non-neoplastic changes such as reactive astrocytosis, inflammatory lesions and infarctions should be excluded. Occasionally, diffuse high-grade gliomas may show extensive epithelial or sarcomatoid changes, and in these cases it is essential to exclude metastatic malignancy. Diffusely infiltrating gliomas must be distinguished from other neoplasms such as so-called “circumscribed” gliomas (pilocytic astrocytoma), ependymal tumors, and neoplasms showing a combination of glial and neuronal differentiation. Histopathologically, glioma tumor cells tend to invade individually or in small clusters the processes of the neuropil and glial cells in the gray and white matter. This arrangement of diffuse infiltrative glioma cells along pre-existing tissue elements is very useful for recognizing a tumor as a diffuse glioma. These arrangements are called "secondary structures of Scherer" after the German pathologist Hans-Joachim Scherer who was a pioneer in studying the growth patterns of gliomas. Morphological Typing of Diffusely Infiltrating GliomasMost diffusely infiltrating gliomas can be morphologically typed as astrocytic, oligodendroglial, or oligomystic. -astrocytic tumors. Astrocytes are stellate cells with an oval to elongated nucleus, little eosinophilic cytoplasm, and delicate eosinophilic cell processes. Astrocytic tumor cells display a mixture of phenotypes with varying degrees of atypia).