I have a slightly lowered immune system and get abscess all the time but normally from an injury or graze, bite etc a few months ago I got a spontaneous swelling. People assumed it was to do with the old injuries (over 6 months old!) I wasn't sure. Then they said blood clot but it kept growing !!! Eventually they kept me in and gave me IV antibiotics. Said they thought it might be an abscess. It was a Thursday and as it went to weekend it just kept growing! I was in agony. Eventually I couldn't walk. But I woke up on Sunday and it looked like it was growing out of my skin ! The skin on top was really fragile because of swelling I pinched it and loads of pus came out. (Sorry no video) when they came round Monday tehy said to operator. They took 3 cups of pus out of my leg. I was also 8 months pregnant at the time. It came to mind as it's finaly healed! My little boys is know 3 months old.
I do have a picture of the cavity it left behind ...