Lecture Notes on Cell Division, Tumors, and Cancer

Balance of Cell Division and Cell Death

• Cell numbers in tissue are regulated by the balance between cell division and cell death.
• Uncontrolled cell division can result in tumor formation.

Types of Tumors

• Benign Tumors
  • Slow-growing and confined by connective tissue.
  • Do not spread to other organs.
  • Can be harmful by pressing on nerves, blood vessels, or brain tissue.
  • Example: Pituitary tumors can press on optic nerves, causing vision loss.
• Malignant Tumors (Cancers)
  • Can spread beyond the original organ to other parts of the body.

Causes of Cancer

• Mutation
  • Cancer starts from DNA damage in a cell, known as a mutation.
  • Occurs during DNA duplication before cell division.
  • Damages are usually repaired before cell division, but some may be ignored and passed on.
  • Affects the genes controlling the cell cycle, potentially causing faster cell division.
  • Usually involves accumulation of many mutations.

Cancer Risk and Predisposition

• Predisposition occurs when an individual is born with a mutation that increases risk of cancer.
• Such mutations make cells more likely to become cancerous, though additional mutations are needed.

Cancer Spread

• Local Spread
  • Cancer cells do not adhere like normal cells and invade nearby tissues and organs.
• Systemic Spread
  • Cancer cells travel to distant organs via blood or lymph systems.
  • Metastasis: Spreading to non-adjacent organs.
  • Cancer cells can start new tumors at distant sites, known as secondary cancers.

Common Sites of Secondary Cancers

• Lungs
  • Common site due to blood flow from most organs going to lung capillaries.
• Lymph Nodes
  • Cancer cells often get stuck in nearby lymph nodes due to narrowing vessels.
  • Surgeons often remove nearby lymph nodes during tumor removal surgeries.