A good deal of strategic choice has been given back to organizations which have become actors of their (only partial) compliance to institutional demands that they in turn contribute to shape. The reported case about the successful modernization of the French Cancer Centers and their reinstatement as the leaders in their field contributes to better understand the role of leadership in institutional change by proposing a positional approach to institutional leadership. Cancer centers' reformers were both central, as they were placed at the intersection of several potentially interdependent organizational fields or institutional spheres, and marginal in most, but not all of them. It was this particular position of the change-entrepreneurs and the relational constraints but also resources coming with it, that both enabled them to initiate a successful drive for the transformation of the field of cancer care, and which also greatly explained the particular form it took. Our analysis underscores the interactive nature of institutional change, where the motor of change structures and simultaneously is structured by the process it is driving and where the initiators of reform have to create their proper and specific combination of old and new in order to build an innovative dynamic.