One day after meeting PLS Cruising Suzy, an Irish Sport Horse “who was all business,” Heather Hartnett entered her in a low-level jumper class and won.
“All I had to do was steer,” Hartnett said. “We were the perfect team.”
By late 2023, Hartnett had moved full-time to Ocala, and the pair continued to advance in their jumping career. But by the end of the next summer, just as they were moving up to 1.15-meter jumps, Suzy started stopping at fences. Hartnett blamed her riding before she and her trainer noticed Suzy’s swollen hock.
“My vet, Dr. Lisa Casinella, couldn’t believe a horse with a hock that looked like that was not lame, but she was not at all,” Hartnett recalled. “I think she is just a very stoic horse with a tremendous work ethic and loves her job.”
After a course of laser therapy yielded no improvement, the next step was a standing CT scan. That’s when Ocala Equine Hospital discovered the mast cell tumor in her right rear tarsal sheath.
Suzy’s case was referred to Dr. Sally DeNotta at UF Veterinary Hospitals in November 2024.
“I will never forget that day. It was surreal,” Hartnett said of Suzy’s arrival at the UF Large Animal Hospital in Gainesville. “Before we got there, Dr. DeNotta and her team had been researching this type of tumor in this location and found very little data. They talked to colleagues around the world, looking for ideas. By the time Suzy and I got there, no stone had been left unturned in trying to come up with a treatment plan.”
Dr. DeNotta had also consulted with Dr. Alison Morton, large animal surgeon and medical director of the Large Animal Hospital, on Suzy’s complicated case. The horse’s imagery showed the tumor had spread throughout the rear leg and beyond.
“This type of neoplasia is benign but can be locally invasive,” Dr. Morton said. “But it doesn’t usually spread to multiple sites, unlike Suzy, who had multicentric disease with it also present in several sites her skin. The ones that are in the synovial structures, like in the tarsal sheath or in joints, are less common and are more problematic because they usually start in these hollow spaces and they’re not noticed until either they cause lameness or they have an obvious bump or swelling in that area.”
After discussing the options, Hartnett chose to start with the more conservative management route, a corticosteroid injection. The mass might not shrink with this treatment, Dr. Morton had advised, but it could potentially keep it from growing further.
“Suzy responded fairly well to that treatment, and from the outside, it looked a lot better. The swelling went down and her soundness was looking pretty good,” Dr. Morton said. “But we were simultaneously monitoring with ultrasonography to look at it, and we could see it was still there.”
Another standing CT scan at the UF Veterinary Hospital at WEC confirmed the tumor was unchanged, and Dr. Morton again presented options ranging from continued maintenance corticosteroid injections to surgery.
As Hartnett spent time thinking about what was best for her beloved riding partner, she continued to work with Suzy and realized the marked difference in how the horse felt to ride. Eventually, Hartnett nervously decided it was worth the risk to go the surgical route.
“It was a challenging surgery, but it went well,” Dr. Morton said, explaining that total removal of this type of tumor is impossible with the way it wraps itself in and around vital structures. “But we got 90-plus-percent of it out, and did a closure that relieves the tension in the skin and placed a heavy bandage to improve the likelihood the incision would heal. She stayed in the hospital about five weeks until she was healed and hand-walking, and she healed perfectly.”
The spirited Suzy tolerated her stall rest and hand walking, followed by a month of easy walking under tack. Months on, she cantered for the first time, and then eventually worked back up to jumping.
“I sobbed after we jumped the first time. I never thought we would get to do that again,” Hartnett said. “And then, just like that, we were back in the show ring at WEC in July and in the ribbons.”
As she nears a year post-surgery, Suzy’s future is bright. “This would never have been possible if Suzy was not in the hands of the team at UF,” Hartnett said. “Everyone was so invested in a positive outcome for my horse and also for me. I feel so lucky to live in Ocala, surrounded by the absolute world’s best veterinary care.”
