By Matt Hladik San Francisco 49ers Pro Bowl left tackle Trent Williams is opening up about the cancer battle that cost him the entire 2019 season. Then a member of the Washington Redskins, Williams first noticed a growth on his head in 2013. However, team doctors said it was not a serious issue. But in 2019, Williams had the growth removed and it turned out to be cancerous. He missed the 2019 season, first because of a dispute with Washington’s medical staff about how they handled his condition and then due to postsurgical soreness which was exacerbated by his helmet. In an upcoming episode of…