I have a completely painless bump attached to my tailbone the diameter of a quarter and 2.5 centimeters at its apex. I am not sure how long it has been there, and when my partner noticed it I first thought it was the end of the tail bone but in actuality is about half-way up. I was recently diagnosed- and am receiving treated for- HIV about six months ago. Since then I’ve been hyper aware of any small thing that seems strange. I’m a 28 yo male, I am a normal BMI and eat well/take care of myself. Is there a possibility of this being cancer, or is it possibly a small deformity of the bone that I never noticed? There is no genetic predisposition in my family for bone cancer.