The precise histogenesis, or cell of origin, for adult HGGs is not known. Current paradigms invoke either the transformation of resident adult neural stem or glial progenitor cells or the de-differentiation of mature glial cells. The classification and grading of HGG is controversial and has undergone a number of modifications in the last few decades. The World Health Organization (WHO) classification system is currently the most widely used system and was born from an effort to provide a consensus for classifying and grading nervous system tumors . In this chapter, we collectively refer to HGGs as those glial neoplasms that correspond to WHO grade III tumors, including AA, AO, AOA, and grade IV tumors, including GBM, giant-cell GBM, and GS. Of note, the gemisto-cytic astrocytoma is classified as a grade II tumor in the WHO classification; however, this tumor type has been associated with a more aggressive clinical course that is similar to grade III tumors, and thus these neoplasms are often also considered in the discussion of HGGs.
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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.