small 5cm mass on my husband's liver

My husband went to the emergency ward because he thought he had kidney stones.  The doctors ordered  a ct scan and they did find some stones but that wasn't causing the problem.  We found out later that it was his back.  The next, the hospital called and they told us that they found a small 5cm mass on his liver.
The hospital did say ,it could be a bunch of blood vessels bunched together or a tumor   Here are my questions!
How accurate is a CT scan in determining a tumor and if the tumor be benign, is surgery needed?