The CEO of an area medical center has stepped down. The Freeman Journal reports that Robert Mason, CEO of Van Diest Medical Center, resigned his position during a special board of trustees meeting on Tuesday. He resigned in order to pursue other opportunities. The trustees accepted the resignation. Mason was tabbed as the interim CEO in November of 2012 before taking the permanent role in 2013. Officials say Des Moines-based Mercy Health Network will provide administrative management support until an interim CEO is named.