Any danger in doing sit ups if I have a m (8 x 10 cm) ......?

that is suspected to be a fibroid? They did a CT scan, doc said they couldn't see exactly where it originates from, and aren't positive it is a fibroid, only that it's a hypervascular m close to the bladder. I can feel it if I lay down for long period of time, then put my hand on my belly, and can actually feel the shape, it's very big, and makes pants not fit well in the waist, though belly doesn't look huge. They want to do hysterectomy, I keep putting it off, she said no suspicion of cancer & def not blood clot, so it was up to me, but she would get it out if it was her. Anyway, could it rupture if it is hypervascular? Is it okay to do sit ups?