I am sorry to hear that you have developed a lump in proximity to where your brain surgery
was performed and that you are unsure what to do about it. Without knowing more about your medical history, or being able to examine you, it will be difficult to give you an accurate assessment of exactly what is going on. However, I can still give you some general ideas, and some of my initial thoughts about what might be going on, and where to go from here. First off, I am not sure when your brain surgery was, but it is possible that the swelling could be related to your surgery. This could be for many reasons; it could be a CSF (the fluid that surrounds your brain) leak into the subcutaneous tissues, which would feel soft and fluctuant like a water balloon. It could also possibly be a small hematoma (blood clot). Another thing that I would want to evaluate you for is a post-operative infection. If your surgery was a long time ago, the swelling could be completely unrelated to your prior surgery, and the swelling could be a lymph node. I recommend that you start out by making an appointment with your neurosurgeon
to evaluate the surgical site and make sure that there aren't any post-operative complications. They should be able to give you a better idea about what is going on.