It is quite common to get benign lesions called hemangiomas on the liver. They are like moles on the skin only in the liver. There are a few reasons why they would send you for a CT AFTER an ultrasound. One, it could look atypical for a hemangioma (which they can sometimes look) so they need better characterization through different bloodflow phases in your liver. Two, it could be difficult to see well enough with ultrasound either due to your body habitus, abdominal gas, or just the location of the lesion. Three, you have a history of having a malignancy before, and they need to rule out metastases (spread) to the liver. Even with typical hemangiomas they are very careful about ppl with previous cancers as mets are very serious.
There are numerous other benign lesions which can occur in the liver, so don't right off the bat think you have cancer. And they usually dont send ppl for a CT when they have a cyst on U/S, we are very good at characterizing lesions if we can see it well enough. The CT will provide more information, and they may follow with biopsy if it still looks suspicious.
Hope this helps

we think, keys for patients with liver disease are:

1) To find the treatment that suitable for your disease condition.
2) To believe there really a treatment in the world accorded with your need.

I hope everyone has the chance to have a healthy liver.