Research has taught us that cancer is a complex disease.
In fact, it is not just one disease but rather a collection of
many diseases that arise when the processes that control
the multiplication and life span of normal cells go awry.
In adults, cell multiplication is a very tightly controlled
process that occurs primarily only to replace cells that die
due to exposure to various external factors or as a result
of normal wear and tear.
If the processes that control the multiplication and life
span of normal cells go awry, the cells start multiplying
uncontrollably, fail to die when they should, and begin to
accumulate. In body organs and tissues, the accumulating
cells form a tumor mass, whereas in the blood or bone
marrow, they crowd out the normal cells. Over time,
some cancer cells within the tumor mass gain the ability
to invade local tissues. Some also gain the ability to spread
(or metastasize) to distant sites.
The progressive nature of cancer provides distinct sites for
medical intervention to prevent cancer, detect it early, or
treat progressive disease. In general, the further a cancer
has progressed, the harder it is to stop the chain of events
that leads to the emergence of metastatic disease, which
is the cause of most deaths from solid tumors.
Changes, or mutations, in the genetic material of a normal
cell are the primary cause of cancer initiation. Over time,
Not all mutations acquired by a cell contribute to cancer
initiation and development. In fact, the identity, order, and
speed at which a cell acquires genetic mutations determine
whether a given cancer will develop and, if a cancer does
develop, the length of time it takes to happen. Numerous
interrelated factors influence mutation acquisition and
determine the overall risk that a person will develop a
particular type of cancer (see sidebar on Why Did I Get
This Cancer? p. 19).
INFLUENCES INSIDE THE CELL
The accumulation of mutations in the genetic material of a
cell over time is the predominant cause of cancer initiation
and progression (see sidebar on Genetic and Epigenetic
Control of Cell Function, p. 20). A genetic mutation is a
change in the type or order of the four deoxyribonucleic
acid (DNA) units, called bases, that make up the genetic
• Cancer is not one disease; it is a collection of diseases characterized by the uncontrolled
growth of cells.
• Many cancers are progressive in nature, providing distinct points for medical intervention
to prevent cancer, detect it early, or treat progressive disease.
• The most advanced stage of cancer, metastatic disease, accounts for most
• Changes in the genetic material in a normal cell underpin cancer initiation
and development in most cases.
• A cancer cell’s surroundings influence disease development and progression.
• The more we know about the interplay among the individual factors influencing
cancer biology, the more precisely we can prevent and treat cancer.
In this section you will learn: