The
Definition
of
Cancer
Cancer
is
a
disease
in
which
some
of
the
body
?
s
cells
grow
uncontrollably
and
spread
to
other
parts
of
the
body
.
Cancer
can
start
almost
anywhere
in
the
human
body
,
which
is
made
up
of
trillions
of
cells
.
Normally
,
human
cells
grow
and
multiply
(
through
a
process
called
cell
division
)
to
form
new
cells
as
the
body
needs
them
.
When
cells
grow
old
or
become
damaged
,
they
die
,
and
new
cells
take
their
place
.
Sometimes
this
orderly
process
breaks
down
,
and
abnormal
or
damaged
cells
grow
and
multiply
when
they
shouldn
?
t
.
These
cells
may
form
tumors
,
which
are
lumps
of
tissue
.
Tumors
can
be
cancerous
or
not
cancerous
(
benign
)
.
Cancerous
tumors
spread
into
,
or
invade
,
nearby
tissues
and
can
travel
to
distant
places
in
the
body
to
form
new
tumors
(
a
process
called
metastasis
)
.
Cancerous
tumors
may
also
be
called
malignant
tumors
.
Many
cancers
form
solid
tumors
,
but
cancers
of
the
blood
,
such
as
leukemias
,
generally
do
not
.
Benign
tumors
do
not
spread
into
,
or
invade
,
nearby
tissues
.
When
removed
,
benign
tumors
usually
don
?
t
grow
back
,
whereas
cancerous
tumors
sometimes
do
.
Benign
tumors
can
sometimes
be
quite
large
,
however
.
Some
can
cause
serious
symptoms
or
be
life
threatening
,
such
as
benign
tumors
in
the
____________________
.