i have had a lump for about a year, it pulsates very badly, even just sitting down. It started as a small lump but recently enlarged at an alarming pace. I went to the docs and had a ct scan, my lump is 12cm now. She has told me to go to hospital urgently as the nature of these is to burst. Not to scare anyone but if left unchecked and they burst, the mortality rate is 100%. so please GO TO THE DOCTOR.