A Francois langur at the Lincoln Park Zoo is back with his family group after undergoing two successful surgeries to remove a cancerous tumor on the roof of his mouth.

“The intervention is the first of its kind,” said Dr. Kathryn Gamble, director of veterinary  medicine at Lincoln Park Zoo.

Dr. Gamble first noticed the tumor in Zhang’s mouth, a type of cancer that had historically only been detected after a monkey succumbs to the disease.

“Lincoln Park identified several years ago that this is a problem for the species with these tumors. And up to this point, it had never been identified at an early enough stage to do something,” Gamble said.

With its early detection, Gamble developed a treatment plan that involved surgery and reached out to RUSH University Medical Center’s director of head and neck surgical oncology Dr. Kerstin Stenson.

“They emailed me and first it was, this is very cool. I want to help,” Stenson said.

After weeks of coordination, Dr. Stenson moved her entire operating room team to the zoo in May 2022 to remove the cancer on the roof of Zhang’s mouth.

Stenson said the surgery was similar to operating on a human, but on a smaller scale.

“His head is the size of a baby's head. The teeth are much sharper. I guess we worked our way around that,” Stenson said.

Zhang did great in surgery and post-op, but the zoo’s veterinary team realized he needed another surgery one year later.

“And so we brought Dr. Kerstin in for a second procedure to help us move things around a little bit to try to cover a little bit more of the exposed bone and he’s done really well with that,” Gamble said.

Zhang recovered from the surgeries by watching cartoons, but Dr. Gamble only allowed him a couple of hours each day.

As he munched on snacks and swung around the primate house, Zhang doesn’t appear to mind. After one more checkup on Dec. 1, he can officially be declared cancer-free.

“We're at 18 months and we don't have tumor back, so we're very pleased with that,” Gamble said.

“It is amazing and just very, very, very humbling,” Stenson said.

Dr. Gamble won’t take credit for saving Zhang’s life.

“I think Dr. Kerstin certainly did and we were able to work together to make sure that he got back with his group and now I think we can say we've saved the whole species line,” Gamble said.

Zhang is the only male with three females in his family group, so there’s high hopes for future langur babies. And now there’s a cancer-fighting process for fellow Francois langurs and potentially other animals as well.

“We have developed a really sound plan that allows us to do what we need to do and make them comfortable,” Gamble said.

“Just how it all came together was, was short of amazing,” Stenson said.