Five days after cancer surgery, Pope Leo stepped to the window and 15,000 people cheered

Pope Leo pledged Sunday to slowly resume his usual activities, greeting crowds in St. Peter's Square in his first public appearance since undergoing surgery for lung cancer five days ago, Reuters reported from Vatican City.

"Having overcome this delicate phase… I will now gradually resume my activities, always with the help of God and your prayers," the 71-year-old pontiff told pilgrims from a window of the Apostolic Palace, speaking in what Reuters described as a firm, clear voice.

Around 15,000 people gathered in St. Peter's Square, according to the Vatican, applauding and cheering when Leo appeared unaided for his weekly midday appointment. One Catholic nun knelt and cried with her hand over her face, while other nuns held a sign reading: "Best wishes, Holy Father. We love you and we are praying for you."

Leo was discharged from Rome's Gemelli hospital on Saturday after doctors said blood tests and chest imaging showed him well enough to return home and carry out normal daily activities independently. Surgeons had removed the lower lobe of his right lung on Tuesday after a nodule found during routine medical checks was diagnosed as lung adenocarcinoma, the most common form of lung cancer.

The pope said Sunday the cancer had been caught at a "very early stage and is well localized," and that his doctors had advised surgery. Specialists following the case said an examination of the nodule during the 90-minute operation had confirmed the diagnosis, and that a full recovery was expected.

He also urged the pilgrims gathered under cloudy skies to set aside selfish ambitions and serve God "without compromise."

For Canada's Catholics — part of a global flock of 1.4 billion — the appearance ends days of anxious waiting. Church and world leaders had offered prayers and wishes for a speedy recovery following the Vatican's announcement of the diagnosis. The Vatican has not said when the pope will hold his next public event; a South America trip is on the calendar for November.