MONTREAL — Canadian National Railway's chief executive is taking a three-month medical leave to battle a rare type of precancerous tumour in his larynx. The country's largest railway (TSX:CNR) said after markets closed Wednesday that Claude Mongeau, 53, will undergo surgery in the coming weeks followed by recuperation and six weeks of radiation to "cure the illness." Mongeau plans to remain "engaged" with CN's business but executive vice-president and chief financial officer Luc Jobin will co-ordinate the railway's leadership team and take direction from the board until Mongeau returns later this fall. "This is a serious health setback for me personally, but one of CN's core strengths is that we have a very experienced and tightly knit senior team that knows how to lead our railway to success," Mongeau said in a news release. "For this reason, I have all the confidence in the world that CN will not miss a beat while I take good care of myself to recover fully." CN transports more than $250 billion worth of goods annually across a rail network spanning Canada and middle America.