I have a bruise on my upper thigh that keeps appearing and disappearing, what could this be? i do have a stent in my heart but i am on no blood thinning medications?

Could you be putting elbow pressure on the upper thigh sometimes that may be causing the bruises is what I wonder because you did not give enough information about how long it last and if the bruising may have be subsequent to like bumping against something. In view of stent in your heart, it means you should still be having regular medical check up. Infections sometimes could cause vasculitis.