Calcified Kidney cyst - risk of being cancerous?

Hi guys...
I am a 21 year old female and I have been very sad and preoccupied since my last visit to my Urologist (about 2 months ago). First I had been there for having UTI symptoms so he ordered a CT Scan to check for kidney stones.
The CT scan showed a 13 mm calcified kidney cyst he told me that this was no cause for alarm and that he wasn't worried about it a bit, since my urine sample also showed no cancerous cells and asked for me to have a follow-up CT scan in 6 mos. Which I will definitely have done the second I can go back to have the scan.
But I just can't rest in peace at night ever since I keep being afraid that this has a potential to become cancer and that maybe the doctor is just trying to keep me calm... but I am not like that the more I notice he's trying to keep me cool the more I freak out.
So I have hopes that here someone will read this and give me honest answers - not that I don't believe my doctor. I do. But I am in need of re-assurance or whatever else I need to know.
Here is what the CT Scan transcription reading says:
"CT and pelvis both without and with IV contrast.
Lung bases are clear. On the non-contrast study there is curvilinear calcification involving the mid to lower pole cortex. No hydronephrosis.
On contrast injection, the liver and spleen are homogeneous and not enlarged. The adrenals, pancreas and gallbladder are unremarkable. The right kidney is of normal size in appearance with normal perfusion function. The left kidney is also normal size with normal perfusion function without evidence of obstruction on either side.
Patient on the post-contrast studies demonstrates the above-mentioned curvilinear calcification actually be a cortical cyst measuring 13 mm in greatest diameter. Does not enhance on post contrast imaging.
On into the pelvis, no free fluid or free air. Visualized bowel is non-obstructed. The appendix is identified and normal in appearance.
IMPRESSION: A 13 mm left renal mid to lower pole partially calcified mildly complex cyst which does not enhance and therefore most likely of benign. Maybe beneficial to do a baseline renal ultrasound with at least one follow up study in 6-12 months' time."

Thanks in advance to everyone that can help me read this transcription.

Sincerely,
Vanessa