Despite erroneous reports that Pope Francis has lived most of his life with just one lung, the surgery actually only removed the upper part of his right lung, and his friends and family say he remains in good health for a 76-year-old man.
The Buenos Aires archdiocese and the Vatican have declined to provide medical reports or specific details about the surgery.
Erroneous reports that his entire lung was removed have appeared in numerous media, including Argentine newspapers and The Associated Press, since as early as 2005, when Bergoglio was considered a potential successor to Pope John Paul II.
But the Vatican spokesman, the Rev. Federico Lombardi, put it this way after Bergoglio succeeded Benedict XVI: "I confirm that many, many years ago he had an operation in which part of a lung was removed." Lombardi added that it wasn't a handicap for Francis, and that "those who know him have always seen him in good health."
The AP could find no record showing Bergoglio himself talking about his lung condition, apart from describing it to two journalists, Sergio Rubin and Francesca Ambrogetti, who wrote his authorized biography, "El Jesuita," and another book published last month, "Pope Francis: Conversations with Jorge Bergoglio."
The "Conversations" book says Bergoglio was a 21-year-old seminarian when he fell feverish and was near death for days.
"The doctors were worried. Finally, they diagnosed a severe lung infection. Because they found three cysts, when his condition was stabilized and a prudent amount of time had passed, he had to undergo the removal of the upper part of his right lung."
"The pain was tremendous," the book continues. "Since then, he's dealt with a pulmonary deficiency that, while it doesn't limit him seriously, it marks a human limit. Surely, that episode strengthened his understanding of what's really important in life."
The pope's last surviving sibling, his younger sister Maria Elena Bergoglio, also told the AP that doctors removed "a pretty big part" of one lung, but said her brother is "completely healthy."
Marco, who served as Bergoglio's spokesman for years in Buenos Aires, said "a good part" of one lung had been removed, but he told the AP that diminished lung capacity seemed to bother Francis less than other ailments that come with old age, such as lower back pain.
That's why he wears orthopedic shoes and uses a cane at times, and "walks kind of crookedly," Marco said.