Fell down stairs, banged shin last July. Recently found hard lump in same area. GP took x-rays, says it's subcutaneous scar. Chances of ST Sarcoma?

Sensitive area. This is a sensitive area and the bone is very close to the surface. If the original injury went completely away this is probably unrelated. Xrays are helpful and sarcoma should be distinctive on plain films. Why do you think it is sarcoma? It is an improbable diagnosis but if there is any question further evaluation is absolutely necessary.