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There are many texts and references
that attempt to define cancer. The simplest definition
is from the
American Cancer Society (ACS). According to the
ACS, cancer is a group of diseases characterized by
uncontrolled growth and spread of abnormal cells. If
the spread is not controlled, it can result in death. |
Characteristics of Cancer
Abnormality
Cells are the structural units of all living things. Each
of us has trillions of cells, as does a growing tree. Cells
make it possible for us to carry out all kinds of functions
of life: the beating of the heart, breathing, digesting food,
thinking, walking, and so on. However, all of these functions
can only be carried out by normal healthy cells. Some cells
stop functioning or behaving as they should, serving no useful
purpose in the body at all, and become cancerous cells.
Uncontrollability
The most fundamental characteristic of cells is their ability
to reproduce themselves. They do this simply by dividing.
One cell becomes two, the two become four, and so on. The
division of normal and healthy cells occurs in a regulated
and systematic fashion. In most parts of the body, the cells
continually divide and form new cells to supply the material
for growth or to replace worn-out or injured cells. For example,
when you cut your finger, certain cells divide rapidly until
the tissue is healed and the skin is repaired. They will then
go back to their normal rate of division. In contrast, cancer
cells divide in a haphazard manner. The result is that they
typically pile up into a non-structured mass or tumor.
Invasiveness
Sometimes tumors do not stay harmlessly in one place. They
destroy the part of the body in which they originate and then
spread to other parts where they start new growth and cause
more destruction. Click here
(Get 
Acrobat
Reader to view and print the file) for a graphic
depiction of an invasive cancer. This characteristic distinguishes
cancer from benign growths, which remain in the part of the
body in which they start. Although benign tumors may grow
quite large and press on neighboring structures, they do not
spread to other parts of the body. Frequently, they are completely
enclosed in a protective capsule of tissue and they typically
do not pose danger to human life like malignant tumors (cancer)
do.
A group of diseases
Although cancer is often referred to as a single condition,
it actually consists of more than 100 different diseases.
These diseases are characterized by uncontrolled growth and
spread of abnormal cells. Cancer can arise in many sites and
behave differently depending on its organ of origin. Breast
cancer, for example, has different characteristics than lung
cancer. It is important to understand that cancer originating
in one body organ takes its characteristics with it even if
it spreads to another part of the body. For example, metastatic
breast cancer in the lungs continues to behave like breast
cancer when viewed under a microscope, and it continues to
look like a cancer that originated in the breast.
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