Signs of lung cancer

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In medicine, cancer is a general term for any of a number of different diseases where some of the body's own cells divide in an uncontrolled manner. The resulting new cells can form a malignant tumor (a neoplasm) or propagate throughout the body.

Malignant tumors such as carcinoma or sarcoma, lymphoma or leukemia originate from a cell or a group of cells in a multicellular organism that has several distinct properties:

  • evading apoptosis
  • Unlimited Growth Potential
  • self-sufficiency of growth factors
  • insensitivity to anti-growth factors
  • increased cell division rate
  • altered differentiation (specialization) ability
  • no ability for contact inhibition
  • ability to invade neighbouring tissue
  • ability to build metastases
  • ability to promote blood vessel growth (angiogenesis)

A cell that degenerates into a tumor cell does usually not acquire all these properties at once, but its daughter cells are selected to build them. This process is called cellular evolution. A first step in the development of a tumor cell is usually a small change in the DNA, often a point mutation, which leads, among other things, to a genetic instability of the cell. The instability increases to a point where the cell loses whole chromosomes, or has double ones. Also, the DNA methylation pattern of the cell changes, activating and deactivating genes more or less at random. Cells that divide at a high rate, such as stem cells, show a higher risk of becoming tumor cells than those which divide less or not at all, for example neurons. If the initial tumor cell (or group of tumor cells) is not removed by the immune system, it will develop into cancer.