Other Astrocytic Tumors

Abstract

Gliomas with a more circumscribed growth pattern most frequently are pilocytic astrocytoma, subependymal giant cell astrocytoma, and pleomorphic xanthoastrocytoma and are categorized as other astrocytic tumors. Pilocytic astrocytomas, WHO grade I are low-grade astrocytomas, more frequently found in children and young adults, imaging most commonly shows typical solid–cystic appearance, histology is characterized by biphasic pattern with variable proportions of compacted bipolar cells with Rosenthal fibers and loose, textured, multipolar cells with microcysts and occasional granular bodies (WHO 2016). These lack IDH mutations and commonly demonstrate the KIAA1549-BRAF fusion gene. The pilomyxoid astrocytoma is a variant of pilocytic astrocytoma histologically characterized by the angiocentric arrangement of monomorphous, bipolar tumor cells on a prominent myxoid background (WHO 2016). It is commonly encountered in infants and young children (median age 10 months). Rapid growth, local recurrence, and CSF spread makes a less favorable prognosis than pilocytic astrocytoma. Subependymal Giant Cell Astrocytoma, WHO Grade I is a benign, slow-growing tumor composed of large ganglionic astrocytes typically arising in the wall of lateral ventricles (WHO 2016). It is frequently associated with tuberous sclerosis syndrome and commonly occurs in the first two decades of life. Pleomorphic Xanthoastrocytoma, WHO Grade II is a superficially located cerebro-meningeal tumor, most frequent in the temporal lobe. It is defined as an astrocytic glioma with large, pleomorphic, and frequently multinucleated cells, spindle and lipidized cells, a dense pericellular reticulin network, and numerous eosinophilic granular bodies (WHO 2016). The presence of BRAF V600E mutations and the absence of IDH mutation supports the diagnosis of pleomorphic xanthoastrocytoma. Anaplastic Pleomorphic Xanthoastrocytoma, WHO Grade III is (APXA), an extremely rare primary brain tumor, is a WHO grade III astrocytoma histologically defined by increased mitotic activity (≥5 mitoses/10 high-power field), with or without necrosis, and clinically notorious for its poor prognostic outcome compared to its benign variant the pleomorphic xanthoastrocytoma (PXA), a low-grade astrocytoma with more favorable prognosis first described by Kepes et al. in 1979.