TOKYO (Reuters) - Japan's Empress Emerita Michiko underwent surgery for early-stage breast cancer at a Tokyo hospital on Sunday, national broadcaster NHK said.
The four-hour procedure to remove cancerous tissue from the 84-year-old's left breast was completed successfully at the University of Tokyo Hospital, NHK said.
NHK said the country's Imperial Household Agency would make an official announcement later in the day.
According to the broadcaster, by around 0530 GMT, Michiko had returned to her private room at the hospital following her surgery, which was performed under general anaesthesia.
Emperor Emeritus Akihito had visited the hospital earlier on Sunday and was due to return later in the day.
Michiko was diagnosed with Stage 1 breast cancer in August.
Accompanied by her daughter Sayako, she was hospitalised on Saturday, her first stay since she underwent treatment for shingles in 1997.
After three decades as Japan's heads of state, Akihito and Michiko stepped down in April, handing over to their son, Naruhito.
Akihito, 85, has had treatment for prostate cancer and heart surgery.
(Reporting by Naomi Tajitsu; Editing by Michael Perry)