“Case of the Month” – November 2019

Riley, a 14-year-old Irish terrier, was referred to the UC Davis veterinary hospital for a dental examination in December 2015. Upon examination by the Dentistry and Oral Surgery Service, a pea-sized black mass was discovered on the roof of his mouth. Veterinarians suspected the mass to be an oral melanoma tumor—a cancer that could be fatal within 3-6 months if not treated aggressively—and submitted a tissue sample for biopsy.  

The dentistry team also called in specialists with the Oncology Service for consultation. To see if Riley had any systemic problems or spread of his tumor, the oncologists worked with the Diagnostic Imaging Service to perform an ultrasound, which showed a mass on his spleen and potentially cancerous testicular nodules. Those discoveries could wait, however, until his immediate oral issue was addressed.

When results of the biopsy were returned, the oral mass proved to be cancerous, so a surgery date to have it removed was scheduled. He underwent oral surgery a few weeks later in January 2016, which required a portion of Riley’s upper jaw to be removed. He recovered well during his 5-day hospitalization, during which the Oncology Service again worked with the Diagnostic Imaging Service to repeat an abdominal ultrasound of Riley’s spleen to check the size of that mass. No signs of size increase were observed.

During Riley’s hospitalization, the oncology team discussed various treatment options for oral melanoma with his owner, Tamar June. Just because the tumor was removed, Riley was not necessarily “out of the woods.” Oncologists discussed with June that melanoma is a cancer that can be aggressive and spread throughout the body. However, Riley had a few things working in his favor including the small size of his tumor, the fact that there was no evidence of spread to his lymph nodes or lungs, and the low mitotic index of his tumor – a cell count that indicates severity of cancer.

Even with complete removal of small melanomas, the disease can spread months or years down the line. For that reason, Riley received additional therapies after removal of his tumor. One therapy discussed with June was a melanoma vaccine called ONCEPT that is meant to prime the immune system to remove cancer cells remaining in the body. The vaccine was known to be safe, but it was not known whether this would benefit dogs like Riley.

June elected to move forward with starting Riley on the melanoma vaccine protocol. He received his first dose while hospitalized and then received three more doses of the vaccine every two weeks. Following those four doses, Riley received a booster every six months, along with chest x-rays to check for any potential cancer spreading.

Upon several re-check examinations with the Oncology Service over the next few months, Riley did not show any signs of local recurrence of the oral melanoma. The left lymph node under his chin was slightly enlarged, though. Due to the fact that melanomas can readily spread to the lymph nodes, it was recommended that his left node be removed.

In May 2016, surgeons with the Soft Tissue Surgery Service removed the enlarged node and his spleen, given the previously identified mass, as well as performed a neuter to address the potentially cancerous issues discovered in those areas previously. Luckily, none of these yielded findings that required follow-up, and no cancer was identified in the lymph node or spleen.   

Over the past three years, UC Davis veterinary oncologists have kept a close eye on Riley. He is now on his 10th round of the melanoma vaccine. Thanks to his veterinarians catching the cancer early, Riley is healthy and happy at 14 years old!

“We’re happy we caught the cancer early,” said June. “Given his age, he’s in great shape. He’s still very active and energetic.”

Riley is scheduled to visit the UC Davis veterinary hospital soon to receive his 11th round of the melanoma vaccine.

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Riley’s case is an example of how the collaborative nature of our veterinarians benefits all of our patients. Collaborative care among specialty services will expand and become more efficient in the future UC Davis Veterinary Medical Center. Learn more about this exciting new vision.