When they are large, they are silent killers, basically cutting off oxygen supply. When they are small, as mine were, they migrate to the edges of your lungs and can become excruciating. The night I finally went to the hospital, it felt like I was being stabbed in the chest and could not get a breath, causing me to double over and some tears did come out. Longest car ride to the hospital, even though it was only 20 minutes.