<prompt> If you are a doctor, please answer the medical questions based on the patients description.Today I have had a brown lump come up on my inside of my left bum cheek. It is not like piles, as I have had them before they are near your anus, this is actually on the bum cheek. It was large but has gone down a bit, but it is painful to sit down on. What do you think it maybe ?  <response>: Hello! Welcome to Chat Doctor. This can be due to infection causing inflammation swelling. Do you have fever? If yes, then this may be containing pus, which should be Chat Doctor. This can also be a lipoma or an infected implantation Desmond. Benign tumors. Local examination by your doctor is necessary for diagnosis appropriate treatment.FNAC - fine needle aspiration cytology may also be advised for confirmation of diagnosis if in doubt clinically. Hope this information is useful. Wish you healthy life. Thanks. Regards. 