Tractability results for the Double-Cut-and-Join circular median problem
  The circular median problem in the Double-Cut-and-Join (DCJ) distance asks to find, for three given genomes, a fourth circular genome that minimizes the sum of the mutual distances with the three other ones. This problem has been shown to be NP-complete. We show here that, if the number of vertices of degree 3 in the breakpoint graph of the three input genomes is fixed, then the problem is tractable 
Ahmad Mahmoody-Ghaidary and Cedric Chauve and Ladislav Stacho
cs.DM cs.DS