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Diffuse astrocytoma is an infiltrating type of glioma (World Health Organization grade II), which even with histopathology, is difficult to diagnose. Magnetic resonance imaging (MRI) is the cornerstone for diagnoses and follow-up of brain gliomas. This report describes a case of diffuse astrocytoma in a 48-year-old man who presented with sudden right-sided weakness and repeated convulsive attacks. On brain computed tomography, the case was diagnosed and treated as an acute infarction. Ten days later, the patient returned with a total loss of consciousness. Brain MRI images revealed an irregularly outlined lesion involving the splenium of the corpus callosum that extended into the left periventricular parietal lobe of the brain with cystic foci in the septum pellucidum. Contrast-enhanced and new sequences of MRI was helpful in approach to diagnosis because of its superior tissue characterization. The histopathology results ultimately confirmed the diagnosis of diffuse astrocytoma. The patient died postoperatively.

Neurofibromatosis type 1 (NF1) is one of the most common genetic neurocutaneous disorders, and it is well known to be associated with peripheral or central nervous system malignancies. The most common malignant tumors are malignant peripheral nerve sheath tumors (MPNSTs); MPNSTs are the most common cause of death in patients with NF1. Central nervous system malignancies rarely occur. So far, the occurrence of spinal cord malignancies is exceedingly rare. Herein, we report a rare case of a 69-year-old male with NF1 following tumor resection twice for cutaneous MPNSTs developing intramedullary diffuse astrocytoma in the conus medullaris, which initially presented with traumatic spinal cord injury associated with a compression fracture from fall. Contrast-enhanced magnetic resonance imaging and biopsy of the spinal cord were required to establish the final diagnosis.

The authors describe a usual case of infiltrative low-grade glial neoplasm with a marked enhanced area which is difficult to diagnose. A 42-year-old man had the diffuse mass lesion partially with apparent enhancement in the right temporal lobe, the insular, and the basal ganglia regions. Final pathological diagnosis from the removed specimens was IDH-wildtype diffuse astrocytoma according to 2016 WHO classification, although it had unusual findings including gliomesenchymal reaction. The nodule-like enhancement was thought to be owing to the mesenchymal component. Several molecular analysis including pyrosequence analysis, Ion Torrent™ next-generation sequencing and multiplex ligation-dependent probe amplification analysis detected no genomic abnormality. IDH-wildtype diffuse astrocytoma is a heterogeneous category and has a minor subset with a silent genomic landscape like the present case.

Background: The natural history of diffuse astrocytomas is thought to have a median time to malignant progression of 4–5 years. Nonetheless, the genetic changes in non-progressive tumors is still being established. Case description: We describe a 22 year old female with gross total resection of a left frontal astrocytoma followed by radiation and chemotherapy in 1993. Twenty-five years later she remains stable, without recurrence. Retrospective microarray comparative genomic hybridization (aCGH) found a 28.6 Mb duplication at 3q26.2q29 and a 9.9 Mb deletion at 20p12.1p11.1. Conclusions: The case illustrates the importance of young age and gross total resection in determining the prognosis of patients with astrocytomas. It also illustrates that occasional variance of natural history may be associated with unique genomic changes. Keywords: Astrocytoma, Long term survival, Chromosome 3p duplication, Chromosome 20p deletion

Gangliogliomas comprise of less than 1% of all primary brain tumours. Malignant transformation is rare. Correspondingly, secondary gliosarcomas, especially in the absence of previous irradiation exposure is too, exceedingly rare. Recent evidence supports the use of mutant IDH1 testing in suspected adult gangliogliomas as a distinguishing feature between ganglioglioma and early diffuse astrocytoma. The authors report a case of a ganglioglioma (WHO I) in the cingulate gyrus that underwent malignant transformation and propagated into a multi-lesional gliosarcoma (WHO IV glioblastoma variant). A previously well 59-year-old lady presented with first-onset focal seizures secondary to a left cingulate gyrus lesion. Stereotactic biopsy of the lesion demonstrated an IDH1 (R132H) ganglioglioma. The patient remained well until a routine follow-up MRI performed 36 months later showed significant progression of the initial lesion and a new, separate lesion in the left temporoparietal lobe. Surgical excision was performed. The final histology reported a gliosarcoma. In view of the unusual findings, the case is reviewed corroboratively with current disease understanding. Keywords: Ganglioglioma, Gliosarcoma, Isocitrate dehydrogenase 1

Historically, oligodendrogliomas have been defined morphologically as glial tumors marked by cells with rounded nuclei and scant cytoplasm. In the most recent revision to the World Health Organization classification of brain tumors, the definition of oligodendroglioma has been expanded to incorporate certain molecular findings, notably mutations in the isocitrate dehydrogenase genes (IDH) and deletions on chromosomes 1p and 19q. The purpose of this chapter is to review the classic morphologic features of oligodendrogliomas and to provide an overview of the key molecular pathologic findings utilized in clinical practice. This chapter will also consider morphologic differential diagnostic considerations including lesions such as diffuse astrocytoma, neurocytoma, dysembryoplastic neuroepithelial tumor and clear cell ependymoma, and discuss how to distinguish these look-alikes from oligodendrogliomas.

The infiltrative or “diffuse” gliomas include astrocytomas and oligodendrogliomas. Taken together, these are the most frequent primary neoplasms of the central nervous system parenchyma. These tumors are difficult to manage clinically, in large part because of their widespread invasiveness, their strong tendency toward biologic progression, and the resistance of many of these neoplasms to conventional adjuvant therapies. The WHO classification currently divides diffuse gliomas into astrocytomas and oligodendrogliomas and includes criteria for their grading. The category of “oligoastrocytoma” is no longer supported, since these lesions have been demonstrated to represent either astrocytomas or oligodendrogliomas at the molecular genetic level. Diffuse astrocytoma (WHO grade II), anaplastic astrocytoma (WHO grade III), and glioblastoma (GBM; WHO grade IV) form a malignancy continuum for the diffusely infiltrating astrocytomas. The diffusely infiltrative astrocytomas of adults are now subdivided based on the mutational status of isocitrate dehydrogenase-1 or -2 (IDH1/2) genes into either IDH-mutant or IDH-wildtype for each grade. Another form of diffuse high-grade astrocytoma that most often occurs in the pediatric population is characterized by histone H3F3 mutations and occurs either in the midline (K27 codon mutations) or in the cerebral hemispheres (G34 codon mutations). The oligodendrogliomas include WHO grade II and III designations and are defined histologically and by the presence of IDH mutations and the codeletion of the entire 1p and 19q chromosomal arms.

Publisher Summary This chapter discusses the pathological, clinical, and molecular aspects, prognostic features, and treatment issues of diffuse astrocytomas, and focuses primarily on WHO grade I pilocytic astrocytomas (PA) and WHO grade II diffuse astrocytomas, and emphasizes that they represent very distinct clinical entities. Diffuse astrocytoma is the most common astrocytoma, because its cells produce neuroglial fibrils, this tumor is firm and rubbery. Unlike oligodendrogliomas, which frequently demonstrate losses of 1p and 19q and rarely have p53 mutations, many WHO grade II diffuse astrocytomas demonstrate loss of chromosome 17p, and roughly half harbor p53 mutations. The chapter suggests that disruption of either the TP53 or the p14ARF pathway is frequent in low-grade astrocytomas and correlates with an unfavorable clinical course. The adverse prognostic factors include poor performance status, tumor contrast enhancement, cognitive dysfunction, focal neurological deficits, and steroid dependency. Treatment options include surgical resection, radiation, and chemotherapy; however, surgery is the primary treatment. Although chemotherapy has been used to treat young patients with PAs at inaccessible sites, such as the optic pathways, but evidence supporting a routine role for this modality in PAs is lacking.

Primary brain tumors, accounting for fewer than 2% of all cancers, are among the most costly to society. Low-grade gliomas represent 10% of these primary tumors. The descriptive names that we apply reflect microscopic appearances and immunohistochemical staining characteristics as well as locations within the nervous system. The terminology is confusing, and the names do not reflect biological behavior, response to therapy, prognosis, or molecular alterations. Astrocytic tumors predominate (diffuse astrocytoma, pilocytic astrocytoma, subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma), followed by oligodendroglial (oligodendroglioma) and mixed glial tumors (oligoastrocytoma). Tumors of mixed glial-neuronal populations also occur (ganglioglioma, desmoplastic infantile astrocytoma, ganglioglioma). Least common are growths in proximity to the ventricles and choroid plexus (choroid plexus papilloma), the ependyma (ependymoma, myxopapillary ependymoma), subependymoma, and neuroepithelial tumors of unknown origin (dysembryoplastic neuroepithelial tumor, chordoid glioma of the third ventricle). Some of these tumors are discussed elsewhere in Part VII of this book. Central to this chapter and to the care of afflicted patients are two tenets. First, low-grade glioma is a descriptive term and does not imply a benign clinical course. A "benign" infiltrating astrocytoma of the brainstem can lead to disability and death; a similar lesion in the optic chiasm causes blindness, and intramedullary spinal low-grade glioma can produce irreversible paraplegia. Second, because many patients survive their tumors, the clinician must weigh the gains of therapy against the side effects of surgery, irradiation, and chemotherapy.