This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': '"Pseudopalisading" arrangement of malignant cells is characteristic of: \nSelect and explain. \nA. Glioblastoma, B. Ependymoma, C. Oligodendroglioma, D. Medulloblastoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: "The highest grade tumor of astrocytoma, known as glioblastoma, has a histologic appearance similar to\xa0anaplastic astrocytoma with the additional features of necrosis and vascular or endothelial cell\xa0proliferation and pseudo-palisading nuclei."\n\nGlioblastoma is type of infiltrating astrocytoma (Classified as Grade 4).\nNecrosis in glioblastoma often results in a SERPENTINE pattern in areas of hyper-cellularity.\nTumor cells collect along the edges of the necrotic regions, producing histologic pattern referred to as\xa0pseudopalisading pattern.\n\nGLIOMAS\nGliomas are tumors of the brain parenchyma that histologically resemble different types of glial cells. The\xa0major types of tumor in this category are:\na. Astrocytomas\nb. Oligodendrogliomas\nc. Ependymomas.\n\nASTROCYTOMAS\n\nTwo major categories of astrocytoma, infiltrating and non-infiltrating types.\nInfiltrating astrocytomas account for about 80% of adult primary brain tumors.\nThey are most frequent in the fourth through sixth decades.\nThey are usually found in the cerebral hemispheres.\nThe most common presenting signs and symptoms are seizures, headaches and focal neurologic deficits\xa0related to the anatomic site of involvement.\nInfiltrating astrocytomas show a spectrum of histologic differentiation that correlates well with clinical\xa0course and outcome.\n\nBased on the degree of differentiation, they are classified into four groups:\n\nPilocytic astrocytoma - Grade I - Most common\nAstrocytoma - Grade 2\nAnaplastic astrocytoma - Grade 3\nGlioblastoma multiforme - Grade 4 - Least differentiated\n\nPILOCYTIC ASTROCYTOMA\n\nPilocytic astrocytomas are relatively benign tumors, often cystic, that typically occur in children and\xa0young adults.\nThey are usually located in the cerebellum; also in the floor and walls of the third ventricle, the optic\xa0nerves, and occasionally the cerebral hemispheres.\nA pilocytic astrocytoma is often cystic, with a mural nodule in the wall of the cyst; if solid, it is usually\xa0well circumscribed.\nThe tumor is composed of areas with bipolar cells with long, thin “\'hairlike” processes that are GFAP\xa0positive: Rosenthal fibers, eosinophilic granular bodies, and microcysts are often present.\nNecrosis and mitoses are absent.\n\nOLIGODENDROGLIOMAS\n\nThese tumors constitute about 5% to 15% of gliomas and are most common in the fourth and fifth\xa0decades.\nPatients may have had several years of neurologic complaints, often including seizures. The lesions are\xa0found mostly in the cerebral hemispheres, with a predilection for white matter.\nOligodendrogliomas are infiltrative tumors that form gelatinous, gray masses, and may show cysts, focal\xa0hemorrhage and calcification.\nOn microscopic examination, the tumor is composed of sheets of regular cells with spherical nuclei\xa0containing finely granular chromatin (similar to normal oligodendrocytes) surrounded by a clear halo of\xa0cytoplasm.\nThe tumor typically contains a delicate network of anastomosing capillaries. Calcification, present in as\xa0many as 90% of these tumors, ranges from microscopic foci to massive depositions.\nWith increasing cell density, nuclear anaplasia, increased mitotic activity and necrosis, the tumor\xa0becomes higher grade (anaplastic oligodendroglioma.)\nPatients with oligodendrogliomas have a better prognosis than do patients with astrocytomas.\nCurrent treatment with surgery, chemotherapy, and radiotherapy yields an average survival of 5 to 10\xa0years.\nPatients with anaplastic oligodendroglioma have a worse prognosis.\n\nEPENDYMOMAS\n\nEpendymomas most often arise next to the ependyma-lined ventricular system, including the central\xa0canal of the spinal cord.\nIn the first two decades of life, they typically occur near the fourth ventricle and constitute 5% to 10%\xa0of\xa0the primary brain tumors in this age group.\nIn adults, the spinal cord is their most common location; tumors in this site are particularly frequent in\xa0the setting of neurofibromatosis type 2.\nBecause ependymomas usually grow within the ventricles. CSF dissemination is a common occurrence.\nIn the fourth ventricle, ependymomas are typically solid or papillary masses extending from the floor of\xa0the ventricle.\nThese tumors are composed of cells with regular, round to oval nuclei with abundant granular chromatin.\nBetween the nuclei there is a variably dense fibrillary background.\nTumor cells may form round or elongated structures (rosettes, canals) that resemble the embryologic\xa0ependymal canal, with long, delicate processes extending into a lumen. More frequently present are\xa0perivascular pseudo-rosettes in which tumor cells are arranged around vessels with an intervening zone\xa0consisting of thin ependymal processes directed toward the wall of the vessel.\nAnaplastic ependymomas show increased cell density, high mitotic rates, necrosis and less evident\xa0ependymal differentiation.\nThe clinical outcome for completely resected supratentorial and spinal ependymomas is better than for\xa0those in the posterior fossa.', 'role': 'assistant'}]