POWELL (WCMH) — The Columbus Zoo and Aquarium says Colo the gorilla is doing well after a two-hour medical examination Saturday morning.

Zoo staff wanted to take a closer look at a mass that developed under one of Colo’s arms. Veterinarians took tissue samples from the mass Saturday to conduct a biopsy, the zoo said.PHOTOS: Colo’s 59th birthday celebration 

Colo is the oldest zoo gorilla on record; she turns 60 on December 22. She made history when she was born, as she was the first gorilla ever born in a zoo.