Pain inside the left buttock can be caused by the following diseases: First, neurofibromas occurring in the lower extremities, usually multiple, or in a few patients, single, are distributed along the direction of nerve travel, and the patient has significant pain and also perceives a local swelling or mass. On examination, the lesion is smooth, well-defined and mobile, and is clearly painful to the touch. The most effective treatment after diagnosis is surgery, usually under local anesthesia or epidural anesthesia, to excise and peel the lesion intact, and postoperative histological examination is also required. Second, it can also occur in the skin folliculitis, sebaceous cysts secondary to infection, serious patients will also appear fever, if necessary, also need to choose surgery to remove.