Law Kar Ying went to China earlier this month to film a movie and posted photos on social media of him having dinner with the crew.
The 72-year-old Hong Kong actor looked to be in high spirits and good health in the photos.
However, unknown to the crew members, he had just gone for an operation to remove his prostate. This was disclosed to the Hong Kong media when he attended a seminar on Saturday (July 13).
The Cantonese opera doyen was diagnosed with liver cancer in 2004, but recovered after operations and treatments.
Law said on Saturday that doctors found cancerous cells after he went for a prostate biopsy several months ago. He went to the hospital late last month for an operation to remove the prostate.
He said he is now on the road to recovery, but suffers from urinary incontinence - a side effect of the operation. He said he has to wear diapers for three to four months.
"It is better to go for the operation earlier as your body may not able to stand it when you are older," he was quoted by Hong Kong's Ming Pao Daily News as saying.
Law, who is married to 71-year-old actress Liza Wang, said his wife has urged him to take care of his health and sleep early as he is used to sleeping at 1 to 2am. He has to go for health screenings every four months.
The veteran actor, known for his professionalism, said he will return to China later for a week to film a television serial. He is also in talks with producers Raymond Wong and Eric Tsang for a role in a new movie.
Law became a movie star after gaining fame as part of a famous Cantonese opera family. He is known for starring in several of actor-director Stephen Chow's movies, such as From Beijing With Love (1994), the two-part A Chinese Odyssey (1995) and Forbidden City Cop (1996).
He married Wang in 2009 after a 20-year courtship.