POWELL (WCMH) — The Columbus Zoo and Aquarium says Colo the gorilla will undergo a “comprehensive” medical examination to examine a mass that zoo staff observed under one of her arms.

Colo, who is almost 60, is the oldest gorilla currently living at a zoo. Columbus Zoo staff say the mass under the gorilla’s arm has been making her “noticeably uncomfortable.”

Zoo staff plan to conduct a biopsy on tissue from the mass. Colo will be under anesthesia for the surgery, which does carry some risk. Zoo staff said in a press release that the risk of ignoring the mass is greater than the risk of examining it.

The zoo says “a highly trained and experienced team will conduct the procedure, including three full-time veterinarians, two full-time veterinary technicians, a cardiologist, an anesthesiologist and an ultrasound technician from Ohio Health, and a veterinary surgeon from MedVet.”