Placido Domingo returned to the operatic stage after cancer surgery to loud applause -- and some dissenting boos -- for his baritone role of Simon Boccanegra at Milan's challenging La Scala on Friday. “La Scala is always La Scala. There were one or two people ... They are entitled to their opinion,” Domingo said after the three-hour performance, which gives him fewer high notes than his famous tenor roles. Most of the audience warmly applauded Domingo and the rest of the cast in Giuseppe Verdi's opera, throwing carnations on to the stage and emphasizing their appreciation at his return with whistles. “I think for most people it was a really lovely evening,” Domingo said. “I really enjoyed it. He has a great voice,” said Ana Pelucarte, an engineer from Venezuela. Domingo had surgery to remove a malignant polyp from his colon in New York last month and has exhorted others to take tests for cancer earlier than he did to avoid similar problems. He made his debut in the baritone role of Boccanegra at London's Royal Opera House last year. Tenor voices often lower in register as singers grow older. Domingo, the sole performer left of the famed “Three Tenors” after Luciano Pavarotti died of cancer in 2007 and Jose Carreras announced his retirement last year, told Reuters he did not have a preference for baritone or tenor roles. “I just love singing,” he said backstage, wearing the dark blue silk cloak of the final death scene and holding a bunch of red and white carnations. Soprano Anja Harteros, who sings the part of Boccanegra's daughter Maria, received the loudest accolade among the other singers for a vivid performance in love and grief. Domingo will sing in another five of the eight performances of Simon Boccanegra at La Scala, ending on May 7.