I'm a healthy 28 year old woman and a few months ago discovered a golf ball sized lump in between my rib cage that moved (usually down and/or to the left) that pulsates. I've also experienced dizziness/lightheadedness; usually in the evening, which is typically when I notice the lump.
It is slightly tender to the touch and only a couple days ago I've begun to feel nauseous and felt some slight sharp pain.
I went to the doctor a couple months ago and she didn't seem concerned (constipation, among a few others, was a guess).
If anyone has insight or has Alison experienced this, I'd be happy to hear!