"I had some skin cancer removed a couple of days ago, and it had no effect (on Friday)," he said to reporters when asked about what appeared to be a small cut on his neck.
Manager Matt Williams confirmed there was no thought given to having Fister skip a start. "No, the doctors said there's no issues, they went in and did what they had to do," said the skipper.
Fister, 30, will continue to undergo tests and have his condition monitored. He is 12-4 with a 2.38 ERA (156 ERA+) in 19 starts and 124 2/3 innings for Washington this year.
The Nationals acquired Fister from the Tigers in an offseason trade. He missed the start of the season due to a lat strain.