18 mm thick-walled cyst

I am 35 yo white male, not smoker and lightly overweight with a past history of hypercalcium in urines and a bladder sclerosis (2 bladder stone removal operations).

During the last operation they found a cyst in my right kydney and asked me to follow up (but I do not remember the size!).
At the follow up they said that the cyst is 18 mm and has thick walls therefore a TC is required.

They added however that I should not be worried and stated that the chance that I have something bad is around 2%.
However I have read online that a thick-walled cyst has 50% of being malignant.

The TC is in 3 weeks and I am feeling VERY anxious.

Should I really not be that worried?

[mba1976]

I forgot to say that they found small traces of blood in my urines and I had no visible stones @ ultrasound and I took antibiotics for 1 week.

[Londres70]

Sounds like it is a complex cyst rated a Bosniak I category which carries a 2% chance of this being cancer.  

Complex kidney cysts are rated using Bosniak categories.  

I would be concerned, but not "freaking out" just yet.