Large kidney cyst...cause for concern?

[DEFresh]

I have a large simple cyst in my left kidney. I have read that these cysts are almost always benign, but the problem with mine is that it's growing.

My left kidney measures 11.9 cm. In 2008 the cyst measured 6.1 cm. In early 2014 it had grown to 8.2 x 7.4 cm, and now in Sept. 2016 it measures 8.1 x 8.0 x 8.4 cm.

I don't see how an 8 cm cyst sitting inside an 11.9 cm kidney can be harmless; surely it must be impeding the function of the kidney. How can the kidney properly perform its functions with such a large mass getting in the way? I do not feel any pain or discomfort in the area of the left kidney. Thank you for any feedback.