Necrosis the premature death of cells caused by external factors such as

Necrosis the premature death of cells caused by

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Necrosis: the (premature) death of cells, caused by external factors such as infection, toxin or trauma. Necrotic cells send the wrongchemical signals which prevent phagocytes from disposing of the dead cells, leading to a buildup of dead tissue, cell debris andtoxins at or near the site of the necrotic cells[27]Arterial and venous hypoxia, or the deprivation of adequate oxygen supply to certain areas of the brain, occurs when a tumor makesuse of nearby blood vessels for its supply of blood and the neoplasm enters into competition for nutrients with the surrounding braintissue.More generally a neoplasm may cause release of metabolic end products (e.g., free radicals, altered electrolytes, neurotransmitters),and release and recruitment of cellular mediators (e.g., cytokines) that disrupt normal parenchymal function.Secondary tumors of the brain are metastatic and have invaded the brain from cancers originating in other organs. This means that acancerous neoplasm has developed in another organ elsewhere in the body and that cancer cells have leaked from that primary tumorand then entered the lymphatic system and blood vessels. They then circulate through the bloodstream, and are deposited in the brain.There, these cells continue growing and dividing, becoming another invasive neoplasm of the primary cancer's tissue. Secondarytumors of the brain are very common in the terminal phases of patients with an incurable metastasized cancer; the most commontypes of cancers that bring about secondary tumors of the brain are lung cancer, breast cancer, malignant melanoma, kidney cancer,and colon cancer (in decreasing order of frequency).PathologyMicrograph of an oligodendroglioma,a type of brain cancer. Brain biopsy.H&E stain.ClassificationSecondary brain tumors
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Secondary brain tumors are more common than primary ones; in the United States there are about 170,000 new cases every year.Secondary brain tumors are the most common cause of tumors in the intracranial cavity. The skull bone structure can also be subjectto a neoplasm that by its very nature reduces the volume of the intracranial cavity, and can damage the brain.[28]Brain tumors or intracranial neoplasms can be cancerous (malignant) or non-cancerous (benign). However, the definitions ofmalignant or benign neoplasms differ from those commonly used in other types of cancerous or non-cancerous neoplasms in thebody. In cancers elsewhere in the body, three malignant properties differentiate benign tumors from malignant forms of cancer:benign tumors are self-limited and do not invade or metastasize. Characteristics of malignant tumors include:uncontrolled mitosis (growth by division beyond the normal limits)anaplasia: the cells in the neoplasm have an obviously different form (in size and shape). Anaplastic cells displaymarked pleomorphism. The cell nuclei are characteristically extremely hyperchromatic (darkly stained) and enlarged;the nucleus might have the same size as the cytoplasm of the cell (nuclear-cytoplasmic ratio may approach 1:1,
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  • Fall '18
  • Lundy
  • English, Oncology, Brain tumor, brain cancer, brain tumors, malignant tumors

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