Knots on body - calcium deposits ?

I have a total of four knots on my body, one on my bottom rib at the tip, one on my sternum, two on my jawbone, one is located to the right of my chin and the other one is located on the corner right side of my jaw bone. I had an ultrasound on the one on my rib and it came back abnormal, I have a while before I can see the doctors to find out what they could be. One of my doctors suggested they could be calcium deposits? Is this a possibility? I have been having a lot of pain in my joints lately, but the only pain I feel from the knots is when hard pressure is applied. The are about the size of a pebble, some have a some what rigged texture. My grandmother had bone cancer at the age of 28, and my grandfather had Lung cancer. I believe that my mother also might have had ovarian cancer. Is cancer a possibility?