Cancer is not just one disease. The term refers to a group
of diseases that share two common traits: the uncontrolled
growth of cells and the ability of the cells to spread through
the blood and lymph (a colorless, watery fluid that contains
infection-fighting white blood cells) to other parts of the
is classified by where it starts, even if it has traveled
to another organ. There are many types of cancer that begin
in different tissues and organs of the body. Each type of
cancer has its own characteristics, such as how it grows,
where it spreads, and how it responds to treatment.xii
A cancerous tumor can be classified as in situ, invasive,
or metastatic. The term "in situ" means that the
cancer has not spread and is still in the site where it began.
These cancer cells have not begun to invade nearby tissues,
making the outlook more positive for the patient. "Invasive"
means that the cancer has spread to other parts of the tissue
where it started. The term "metastatic" means the
cancer has spread or started to spread to other parts of the
body. Cells from the primary tumor have broken away and "metastatized,"
or traveled to healthy tissues via the bloodstream or the
lymph system. The tumor at the new site is called a "metastatic
Staging is a process of evaluating the extent of your cancer,
if and where it has spread, and if there are any medical problems
being caused by your cancer.xiv
Staging also gives doctors a way to estimate your outlook
and evaluate your response to treatment. The higher the stage,
the more advanced the cancer. It is important to know, however,
that each type of cancer has its own criteria for staging.