from a very basic standpoint and what i personally know about cysts since i actually have a cystic disease in both kidneys and liver. any 'cyst" is generally some level of actual fluid filled development which can be caused by many many different causes. a tumor on the other hand is normally a more 'solid' type of growth, meaning its inside is solid in form,and not like a cyst filled with fluid. does that make any sense?

while there are many different types of tumors caused for many reasons,thay all tend to have that one component in them,they are solid inside with something. some can grow like with a cancer meaning they are a 'progressive" type of tumor, and some are just a "growth" of tissue that never progress from that form.

is there a particular reason you are asking this question? marcia