Two-time World Championship runner-up Ali Carter has been diagnosed with lung cancer.
World Snooker announced on Saturday that the 34-year-old from Chelmsford will undergo a course of chemotherapy.
Carter, who suffers from Crohn's disease, last year recovered from testicular cancer to resume his career.
World Professional Billiards and Snooker Association chairman Jason Ferguson said: "Ali is the toughest competitor I know and having spoken to him over the last few days I can assure everyone he has the fight to get through the battle ahead."
Ferguson added: "I know that the world will be looking forward to Ali returning to action and I am sure that all of our friends, fans and partners will join with me in wishing Ali a full recovery."
Carter had been due to play on Saturday in Gloucester, in qualifying stages for the Wuxi Classic tournament, but pulled out.
He is a three-time ranking tournament winner, having landed titles at the 2009 Welsh Open, 2010 Shanghai Masters and 2013 German Masters.
Carter lost to Ronnie O'Sullivan in each of his Crucible finals, in 2008 and 2012.
He was diagnosed with testicular cancer last summer but was soon back on tour, and played almost a full season, ending at the World Championship in Sheffield when he beat Xiao Guodong in the first round before bowing out to eventual winner Mark Selby in his next match.
A professional since 1996, Carter is ranked 13th in the world and has been as high as number two in his career. He is also a trained pilot, going by the nickname 'The Captain'.
Snooker has been touched by cancer tragedy in recent memory, with the three-time Masters champion Paul Hunter dying of a rare form of the disease in October 2006, at the age of 27.