The National Cancer Center Hospital has said part of a patient's lung was mistakenly removed during surgery by doctors who thought he had cancer because samples of cells taken from two other patients were mixed up.
The patient, a resident of Tokyo in his 60s, was suffering from a disease called chronic inflammatory mass that required no surgery, the center said Thursday.
About one-third of his right lung was removed earlier this month. The patient has since been released from the hospital.
A laboratory technician put the wrong patient identification seal on cell samples, the center said.
Of the two other patients, one was confirmed with having cancer after surgery, the center said.
The center said about 300 patients undergo surgery even though cancer is unconfirmed. Of them, 20 to 30 turn out to have had no cancer.