A system for treating uterine tissue having a seal assembly configured for positioning in a patient's cervical canal and uterine cavity; an expandable distal balloon portion; an expandable elongate medial balloon portion configured for movement between a first transversely expanded shape for engaging a cervical canal and a second transversely non-expanded shape for trans-cervical insertion; and a fluid source in communication with distal balloon portion and medial balloon portion for expansion of said balloon portions.