DTI or abscess

So....my patient presented with a large (small golf ball size) area of induration to her right ischium. She is elderly (101) but moves around pretty good. At the center is a purple area, irregular in shape. She has no pain when pressure is applied. It was found Friday night and thought to be a abscess..started on abt and warm compresses. The induration has decreased but is still present. I tried squeezing and nothing came out and she denied pain. I’ve never seen a dti with this type of induration... it’s more like a mass....could it just be an abscess or could it be a dti? Has anyone ever noticed induration like I described with a dti?