Multiple 15" Retina MacBook Pro owners are complaining of an annoying fan noise which may be related to Sandisk SSDs
http://www.notebookcheck.net/15-Retina-MacBook-owners-experiencing-fan-noise-problems.89544.0.html
Did this issue get resolved? Did Apple give you a reason for this fan issue? I have the top-of-the-line MBP Retina 15" model and this happens when I render videos.
https://www.ifixit.com/Guide/MacBook+Pro+15-Inch+Retina+Display+Early+2013+Left+Fan+Replacement/17051 - maybe this helps, if you're feeling adventurous. Is your Mac out of warranty yet?