A method of treating a lesion in a body lumen to enlarge a passageway in the lumen including inserting a cutting member and tracking member through a first lumen of a catheter, withdrawing the catheter from the cutting member and tracking member, inserting the catheter over the tracking member and leaving the cutting member outside the catheter, and expanding a portion of the catheter to move the cutting member into cutting contact with the lesion. A device for treating a lesion in a body lumen including a cutting member and tracking member is also provided.