It was reported that Watanabe's decision to go for a medical checkup was due to his wife Minami Kaho's advice. Subsequently, his daughter An recommended a clinic to him where he went for the check-up in early February and had the surgery on the 8th. Watanabe also updated his Twitter account on the same day of the announcement where he thanked his wife and daughter for urging him to go for the checkup and making the arrangements for him.
Although Watanabe was scheduled to perform in the Broadway musical "The King and I" from 1 March to 17 April in the Lincoln Center, he will only return to work from 17 March as he needs to recuperate during this period.
Watanabe was diagnosed with acute myelocytic leukemia in 1989 and suffered a relapse in 1994.
Source: Sponichi 1 / Sponichi 2 / Sponichi 3