COLUMBUS (WCMH) — The Columbus Zoo says that a mass removed from the arm of Colo the gorilla was a malignant tumor.

Columbus Zoo and Aquarium veterinarians have received the pathology report for the mass removed from the area under Colo’s arm. The mass was a malignant tumor but the team had removed it with clean, wide margins. The comprehensive medical examination did not indicate the tumor had spread and no additional treatment is planned.

Colo, the first gorilla in the world born in a zoo and the matriarch of the Columbus Zoo’s famous gorilla family, underwent surgery to remove the mass on Dec. 3.

“We are very proud of the team that removed Colo’s tumor. Surgery poses some risk and this procedure required thoughtful consideration and extensive planning,” said Tom Stalf, president and CEO of the Columbus Zoo and Aquarium. “The results of the pathology report make it clear that this surgery was necessary to prevent the tumor from spreading and becoming life threatening.”

Dr. Randy Junge, the Zoo’s vice president of animal health, indicated Colo’s bloodwork is within acceptable ranges for a geriatric patient. At nearly 60 years of age, Colo is the oldest gorilla on record, exceeding her normal life expectancy by more than two decades.

The Zoo team has turned their focus on planning Colo’s historic birthday party on Dec. 22.