Former Empress Michiko was discharged from the University of Tokyo Hospital on Tuesday, two days after undergoing successful breast cancer surgery, the Imperial Household Agency said.
Doctors deemed the 84-year-old former empress was recovering smoothly from the surgery Sunday after observing that her appetite was gradually returning and she could leave her room and walk around.
The former emperor expressed gratitude to the head of the hospital and doctors who conducted the operation, telling them "thank you" before returning to the Imperial Palace by car.
She was admitted to hospital on Saturday to undergo a partial mastectomy to remove cancerous cells while preserving her left breast.
The operation was performed by medical staff from the Shizuoka Cancer Center, which dispatched doctors to carry out breast cancer screenings of the former empress, and the University of Tokyo Hospital.
A lump was found in July in the mammary gland of the former empress's left breast during an echography exam, and the cancer diagnosis was confirmed after a needle biopsy was conducted in early August.
At stage 1, the earliest stage of invasive breast cancer out of four, no tumor cells were detected to have spread.
A decision on whether or not to administer hormone therapy and other treatments will be made based on the results of a final pathological diagnosis of the removed tissue, which will take one to two weeks to complete.
On the day of the surgery, Former Emperor Akihito and the couple's daughter Sayako Kuroda visited the hospital to see the former empress before her operation. The pair also came to the hospital on Monday.
Former Empress Michiko lost weight due to stress and a busy schedule amid the imperial succession earlier in the year, according to the agency. She underwent cataract surgery on both eyes in June and was earlier diagnosed with heart valve abnormalities, with the condition continuing to be monitored.
The former emperor became the first Japanese monarch to abdicate in about two centuries, bringing an end to the Heisei Era spanning his 30-year reign. His elder son Emperor Naruhito ascended the Chrysanthemum Throne on May 1.
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