A New Non-Surgical Option for Some Mast Cell Tumors: Stelfonta

Stelfonta offers an injectiable treatment alternative to surgery for some mast cell tumors in dogs.

At Two Rivers Vet Hospital in Fargo, ND, we’re always exploring treatment options that support your pet’s health with the least stress and the most impact. When it comes to treating mast cell tumors (MCTs) in dogs, one exciting option for certain cases is Stelfonta®, an FDA-approved injectable treatment that dissolves specific mast cell tumors—no surgery required.

Stelfonta is designed to treat non-metastatic cutaneous MCTs and subcutaneous MCTs located at or below the elbow or hock in dogs. It's not for every dog or every tumor, but when the tumor meets the right criteria, Stelfonta can be a powerful option. After a single injection directly into the tumor, most dogs experience tumor breakdown and removal by the body over the course of a few weeks.

This means no anesthesia, no surgical recovery, and minimal disruption for both pets and their people. Like all treatments, Stelfonta has potential side effects—including localized swelling, pain, and discharge as the tumor site heals—but many pet owners are impressed by the convenience and success of this novel therapy.

At Two Rivers, we carefully evaluate each mast cell tumor to determine the best course of action. For some dogs, Stelfonta offers a less invasive alternative to traditional surgery, while others may require more comprehensive care. As always, we’re here to guide you through the best options available.

To learn more about Stelfonta, visit the official website here.

And if your dog has been diagnosed with a mast cell tumor or you’ve found a new lump, schedule an exam with our experienced veterinary team. We’re here to help you make informed, compassionate decisions—every step of the way.