My 9 mo old has a lump near temple since birth dr finally agreed to order u/s; dr thinks it is a dermoid cyst. should mri or ct be done to rule out tumor and cancer?

2nd opinion: At that age, your doctor is giving you the highest probability that it is something benign. However, you can always get a second opinion, from an oculoplastics surgeon. They are very familiar with this type of cyst, and can reassure you what your next step should be. Because if it has to be surgically removed, they are the ones who would be doing it. It's a very simple, short outpatient surgery to do. So, you have nothing to worry about.

Follow your heart: A knot present since birth is not going to be a cancer and a dermoid is considered a benign tumor. A MRI or ct are not going to give you more data than you have already. You would get more info from having a piece of the cyst removed and studied. This can sometimes be approached from behind a hairline or through the brow. Your doc can suggest a good cosmetic surgeon.