I am going to my gp but wha..

Hi yes im 18 now and ever since i can remember since a proberly about 13 or 14 i have had this perfectly round small marble shaped lump under my skin on the outside of my left leg at the very top of calf, where the calve meets the thigh, not quite on the back of my knee but on the side. The lump its self is totally painless, sort of domed shaped, slightly comprisible, has no opening, has no colour to it and seems to be just siting slightly underneath the skin. Obviously i am ging to see my gp and it canot be diagnosed over the web but does any one have any ideas of what it could be? thanxs for your time.

Yes, I agree. It's either a calcium deposit or a fatty corpuscle. It's painless, which is always a good sign. Either way, they should be able to remove it.

It could be a calcium deposit

That's probably a ganglion cyst, also known as tendon cyst. You probably have to get it removed surgically if it's bothering you. Or your doctor can aspirate the contents of the cyst and inject a steroid in it. Sometimes the cyst resolves with the shot. If not, surgery is the only solution.