Good for you for scheduling an appointment
with a doctor.
I do not think it is safe to say that
there is a 100% chance of your having
cancer. You should never try to diagnose
yourself. There are a few different
things that can cause lymph node
reactions.
"Essentially 5 broad etiologic categories
lead to lymph node enlargement
(Ghirardelli, 1999).
* An immune response to infective agents
(eg, bacteria, virus, fungus)
* Inflammatory cells in infections
involving the lymph node
* Infiltration of neoplastic cells
carried to the node by lymphatic or blood
circulation (metastasis)
* Localized neoplastic proliferation of
lymphocytes or macrophages (eg, leukemia,
lymphoma)
* Infiltration of macrophages filled
with metabolite deposits (eg, storage
disorders)"
emedicine.com/ped/topic2975.htm
Sometimes it is actually not serious or
life threatening, so don't worry yet. You
can't worry before you know for sure what
the issue is!

Good luck. Let
us know what the doctor says. When is
your appointment?