Meet Eugene, a three-year-old male guinea pig, who belongs to our senior veterinary technician, Brandi. During his daily head scratching, Brandi noticed that Eugene had a small round bump on his head close to his right ear. Eugene still ate and drank normally and didn’t flinch when she touched it, but Brandi wanted a veterinarian to check out the bump. She brought him to see me the very next day.
After a brief physical examination, I palpated the bump on his head and made a list of things that may cause a bump like this. The list included multiple types of benign tumors, a fatty tumor called a lipoma, and rare metastatic tumors.
Guinea pigs commonly have bumps like Eugene’s called trichofolliculomas. These masses are benign tumors of basal cell origin (meaning they do not metastasize), and they are the most common skin tumors of guinea pigs. They are typically round, can either be firm or soft, and can be closed (like Eugene’s), or can rupture and exude an oily sebaceous discharge. Luckily, these tumors are easily removed with a short surgical procedure. Occasionally, they can even be removed under sedation and a local block only and not require general anesthesia, depending on the location of the mass.
Eugene’s mass was located next to his ear, which can be a sensitive area. Brandi and I used a small amount of gas anesthesia along with sedation and a local block to prevent any pain and to allow for quick removal. A one centimeter, elliptical incision was made around the mass. Blunt dissection allowed complete removal of the mass, and the site was closed with intradermal (under the surface) sutures. We then placed Eugene on oxygen to recover, and he started waking almost immediately. He even ate his hay as soon as he woke up.
Due to the small amount of skin that was removed, Eugene’s right ear stands up a little more than the left, giving him an inquisitive facial expression. This fits his curious personality perfectly!
A veterinarian should evaluate any skin masses on guinea pigs as soon as they are noticed. Most cases are trichofolliculomas and can be easily removed with no serious complications. However, some other skin masses can become infected and cause life-threatening illness, can be malignant (cancerous) tumors, or can grow large enough to make surgical excision difficult. In the more serious cases, early diagnosis is the best way to prevent life-threatening situations.
Dr. Lindsey Woods is a graduate of Oklahoma State University Center for Veterinary Health Sciences who completed two post-graduate specialty internships in avian, exotic pet, wildlife, and zoological medicine. Dr. Woods recently moved to Utah and started her Veterinary Associate position with Dr. Laurel Harris at Wasatch Exotic Pet Care.