It is extremely unlikely, but stranger things have happened. The result would not be very dramatic and serious injury would be unlikely.
SAAMI produced a very good video for firefighers related to ammunition and components, you can preview it here.
Link Removed
The relevance is that even if a dropped round goes off, without being captive in the chamber to build pressure and connected to the shooter to 'push off from', the case and bullet MAY separate, carrying only their individual mass. The case, being lighter than the bullet in most cases, is the component that may take flight. Another outcome is the primer just comes out of the loaded case because the breach isn't there to hold it in the case. None of it worrisome.
Good question - hopefully this is helpful.
Eric