What is cancer, and how does stomach cancer spread?

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.

Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place.

Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor.

Tumors can be benign or malignant:

• Benign tumors are not cancer:
  
  • Benign tumors are rarely life-threatening.
  • Most benign tumors can be removed. They usually do not grow back.
  • Cells from benign tumors do not invade the tissues around them.
  • Cells from benign tumors do not spread to other parts of the body.
  
  
• Malignant tumors are cancer:
  
  • Malignant tumors are generally more serious than benign tumors. They may be life- threatening.
  • Malignant tumors often can be removed. But sometimes they grow back.
  • Cells from malignant tumors can invade and damage nearby tissues and organs.
  • Cells from malignant tumors can spread (metastasize) to other parts of the body. Cancer cells spread by breaking away from the original tumor and entering the bloodstream or the lymphatic system. The cells invade other organs and form new tumors that damage these organs. The spread of cancer is called metastasis.

Stomach cancer can affect nearby organs and lymph nodes:

• • A stomach tumor can grow through the stomach's outer layer into nearby organs, such as the pancreas, esophagus, or intestine.
  • Stomach cancer cells can spread through the blood to the liver, lungs, and other organs.
  • Cancer cells also can spread through the lymphatic system to lymph nodes all over the body.

When cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the original tumor. For example, if stomach cancer spreads to the liver, the cancer cells in the liver are actually stomach cancer cells. The disease is metastatic stomach cancer, not liver cancer. For that reason, it is treated as stomach cancer, not liver cancer. Doctors call the new tumor "distant" or metastatic disease.