Empress Emerita Michiko has had surgery for early-stage breast cancer. The Imperial Household Agency says she will be able to leave hospital in a few days.
The operation was performed at the University of Tokyo Hospital on Sunday. Surgeons removed the cancerous growth, believed to measure around one centimeter, and the surrounding tissue.
The agency quotes doctors as saying the Empress Emerita has stage one cancer, unchanged from the pre-surgery diagnosis.
The agency also says a pathological examination found the cancer had not spread. A final diagnosis is expected in two weeks or so.
The Empress Emerita drank some water after waking up from general anesthesia.
Emperor Emeritus Akihito and the couple's daughter, Sayako Kuroda, accompanied her to the operating theater.
The three were briefed by doctors after the surgery. Agency officials say the couple seemed relieved to hear that the cancer has not spread to other organs.