A woman's kidney that was suspected of being cancerous was transplanted into her son last September at a hospital in Akita Prefecture, according to hospital officials.
The tumor that had been found in the kidney was confirmed to be benign after the operation, the Akita University Hospital officials said Saturday, insisting they had warned beforehand that if the tumor was malignant, the cancer could spread to the son.
Both the mother, in her 60s, and the son, in his 30s, are currently in good condition, the hospital said.
Using questionable kidneys in transplants has recently become a hot issue for Japan's medical community and the government after revelations of such transplants conducted by urologist Makoto Mannami at Uwajima Municipal Hospital in Ehime Prefecture. He is now a senior urologist at Uwajima Tokushikai Hospital.
The Health, Labor and Welfare Ministry is considering a prohibition on using questionable kidneys in transplants.
But experts said the Akita case does not fall into the category of dubious transplants, given that the mother and son clearly consented to the transplant and that careful examinations were carried out before and during the operations.
Kazuo Mizoi, who heads the hospital, said the mother agreed to give her kidney to the son, who was in need of a transplant due to deteriorating kidney functions.
In a preoperation test, however, the mother's kidney was discovered to have a tumor 1 cm in diameter, Mizoi said.
The hospital decided to go ahead with the operation after judging that the possibility of the tumor's malignancy and it spreading were low as a result of clinical imaging diagnosis by urology professor Tomonori Habuchi.