Impression on pet ct scan is listed as: follicle on right ovary with associated hypermetabolic activity. what does this mean? should i be concerned?

Not sure: What really matters is why they did the imaging in the first place. I am going to guess that since you have a history of breast cancer, they were looking for possible distant metastases of this disease. I have personally seen breast cancer spread to the ovaries. If this is their concern, it should be further evaluated.

Depends on cycle.: It depends on whether you were ovulating during the PET scan. If you recently had your period then it is just a normal finding on the scan which shows that your ovaries were releasing an egg from the ovary. However if u have cancer and it has metastasized (spread to other parts of your body ) then it may be a more concerning finding. The doctor reading the scan should know when your LMP was.