The operation, which began around 8:30 a.m., is the first of many Marlie Casseus must undergo.
The teen suffers from a rare form of Polyostotic Fibrous Dysplasia, a nonhereditary, genetic disease that causes bone to become "like a big a bowl of jelly with some bone inside," according to University of Miami School of Medicine's Dr. Jesus Gomez, one of a team of nearly a dozen specialists performing the 14-hour procedure.
Gomez said about 150,000 people worldwide are diagnosed with the disease, but only 3 percent suffer such an extreme condition. He added that Marlie's growth was the largest he had ever seen and that every bone in her body was affected by the disease. Her liver and spleen were already altered because of it.
He said Marlie is in constant pain and must be medicated but should have a normal life span after the operations.
Back home in her native Port-au-Prince, Marlie faced not only physical suffering, but rejection by her neighbors as well.
"She was treated like an animal. If she was walking on a sidewalk, people would cross the street," Gomez said. "If they tried to stop a taxi, it would keep going."
Marlie's mother Maleine Antoine said she had lost hope in Haiti.
"I don't know how to thank you for this," she told doctors through a translator during a hospital press conference Tuesday. "I cannot express my emotions."
The nonprofit Good Samaritan for a Better Life brought the 14-year-old Marlie to the United States for treatment in September after the tumor grew so big it began to crush her breathing passage. At that time, doctors inserted a breathing tube down her throat.
Gomez said doctors at Holtz Children's Hospital would start with the left side of Marlie's skull and carve away the ballooning fibrous mass that has stretched and distorted her face, spreading apart her teeth and all but obliterating her features.
If the operation is successful, they will try to reconstruct the right side of her face and then later her swollen jaw.
Doctors said the tumor could continue to grow through Marlie's adolescence but it was necessary to operate immediately or she would go blind.
The initial operation, paid for with donations from around the world, will cost $95,000 because the doctors waived their fees. The hospital and Good Samaritan said they have yet to raise the funds to fully restore Marlie's features.