A "lytic bone lesions" is an area in which the bone appears to have been eaten away, leaving a clear area. In this case, the CT scan
seems to show that there is a eaten away area of bone in the right parietal bone, which is the bone on the right side of your temple region.
Many times, lytic lesions are because of cancer. In fact, if you have a history of cancer already, then the most likely possibility is that whichever type of cancer you have (for example, breast cancer) has spread to the bone in this region.
In the absence of an existing diagnosis of cancer, there are several other possibilities which might not be cancerous. These could include some types of bone cysts or a certain type of bone infection referred to as osteomyelitis.
Nevertheless, lytic bone lesions are almost always serious and they do often represent cancer. Therefore, you will need to talk with your doctor
who ordered this CT scan to see what they are thinking about this finding and what the next steps might be. They will help you decide what the appropriate treatment is, as they are more knowledgeable about your case as a whole.