Cancer wreaks havoc in almost every part of the human body.
Tumors strike the brain and the gut, muscles and bones. Some
grow slowly; others are more aggressive and expand quickly.
Their presence in human tissues signals chaos and a break-
down of normal function. Cancer brings unwelcome change to
a biological machine that is perfect, marvelously beautiful,
and complex beyond measure. Wherever tumors appear, they
take on the appearance of alien life forms, invaders that enter
the body through stealth and begin their programs of destruc-
tion from within. But appearances deceive: The truth is much
more subtle and endlessly interesting.

Tumors are not foreign invaders. They arise from the
same material used by the body to construct its own tissues.
Tumors use the same components -- human cells -- to form
the jumbled masses that disrupt biological order and func-
tion and, if left unchecked, to bring the whole complex, life-
sustaining edifice that is the human body crashing down.

How are human tissues put together from single cells?
The description above might suggest the involvement of
master builders who oversee crews of workers, directing
them in the detailed construction of normal and malignant

-1-