<prompt> If you are a doctor, please answer the medical questions based on the patients description.I have a lump on my lower back right above my butt crack, it dosent hurt when I bend or sit but it hurts when I lay on it but only on hard surfaces. No puss comes out of it and its not red, It has gotten bigger since I had kids and gained weight, it does hurt when I press on it.  <response>: Hi! Thanks for giving me another opportunity to discuss some early lumps in the posterior midline of our body; as this is common, generally in pediatric age group and do not disturb a persons health! Anyways, what are these? Yes, these are benign; not infective, not cancer and not going to kill you but will cause cosmetic problems, physical inconvenience and fear of getting hurtinfected there... These could be some congenital cyst like Desmondepidermal cyst, lipoma, neurofibroma or a skin fibro-epithelial polypskin tag...!Therefore, get to your surgeon for a direct examination, tests if necessary and to relieve your concerns!regards, 