Leo has been diagnosed with lung adenocarcinoma, the most common form of lung cancer, and doctors removed the lower lobe of his right lung in a surgery on Tuesday afternoon.
The Vatican has said the surgery was completed successfully, without complications.
It has not yet disclosed the size of the tumour or whether the disease had spread to nearby lymph nodes, key factors in determining prognosis.
Blood tests and a chest X-ray carried out on Wednesday showed normal post-operative results, the Vatican said.
US President Donald Trump, who has clashed with Leo on a number of issues, added his voice on Wednesday to the global chorus of goodwill for the ailing pontiff.
"I want to see Pope Leo get well," Trump told reporters.
"I just want to wish him well, get better fast."
Vice-President JD Vance, a Catholic convert, also added his prayers.
"May God grant him strength as he works to get better. I hope he knows that millions of American Christians are thinking about him," Vance wrote on X.
Further updates are expected on Leo's condition on Thursday, but his pathology report might not be available for several days.
Leo's public engagements have been cancelled until October 20.
The cancer diagnosis for a pope known to be relatively young and energetic and who was elected only in May 2025 caused shock and raised questions about the future shape of his papacy as he deals with the illness.
Leo usually has a packed schedule.
He is due to make a tour of Uruguay, Argentina and Peru from November 6 to 17 and the Vatican media office said on Wednesday that "nothing has changed" regarding the planned trip.
However, Peruvian President Keiko Fujimori said the dates could change because of the amount of time that Leo's recovery would take.
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