What Could Cause Pain In Abdomen?

I had an ultrasound done on my right upper abdomen, thought it was due to gall bladder as I had been having some pains, but no other symptoms. The ultrasound showed a 1cm by 2cm shadow on the head of my pancreas.
What could this mean, I am scared to death. Cancer runs in my family (kidney cancer, colon cancer in sisters and I have already had a melanoma in 1995). I am getting a CT scan tomorrow.