Story highlights He returned to work in Washington before flying home to Vermont

Sanders has kept busy the past few weeks

Washington (CNN) Vermont Sen. Bernie Sanders underwent a successful outpatient procedure Thursday to remove a basal-cell carcinoma from his cheek.

The former Democratic presidential candidate returned to work in Washington after the hour-long procedure and later flew back to Vermont.

Sanders, 75, has kept busy the past few weeks and has emerged as a leading critic of President-elect Donald Trump. The senator blasted Trump's pick of Rex Tillerson for secretary of state, calling the decision "very dangerous," and on Saturday, Sanders tweeted that the President-elect was "a pathological liar."