He will go into hospital on Tuesday but it was not immediately clear whether the operation would take place on the same day.
Despite the upcoming procedure, the 71-year-old pontiff continued his official engagements on Monday, attending several scheduled private audiences and a group audience at the Vatican.
Leo announced after Sunday's Angelus prayer that a "nodule in the lung" had been discovered during a routine examination at a "very early stage".
"The doctors consider an intervention appropriate," he said, adding that he had decided to follow their advice and undergo surgery to remove the lump.
Vatican spokesman Matteo Bruni said Leo was expected to remain in hospital for about a week after the operation.
No further medical details have been released.
Gemelli Hospital, on the outskirts of Rome, has a special wing reserved for papal patients.
Leo's predecessor Francis was treated there shortly before his death in April 2025.
Francis had lived with part of one lung removed since his youth.
A lung nodule can have a variety of causes, including previous inflammation or infections, benign growths, lung cancer or the spread of cancer from elsewhere in the body.
A definitive diagnosis often requires a tissue sample or surgical removal, although many nodules discovered during routine examinations are not cancerous.
At 71, Leo is considered relatively young for a pontiff.
He keeps fit by playing tennis, swimming and exercising regularly.
No health problems had previously been publicly reported.
with Reuters
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