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Owner story – STELFONTA® (tigilanol tiglate)

Bruno's STELFONTA journey, told day by day.

A real owner’s guide to STELFONTA treatment, from the injection to recovery over 28 days; medications, home preparation, and the safety facts every dog owner should know.

Read the day-by-day
Quick answer first

Published 8 July 2026 · Medically reviewed by Dr Carly Wilde BVSc (Hons)

Dog with Mast Cell Tumor, treated with Stelfonta
Bruno. Mast Cell Tumor Removed.

QUICK ANSWER

STELFONTA is a vet-only injection given directly into the tumor to treat non-spreading Mast Cell Tumors in dogs.

Most owners notice the tumor change color within four hours, soften and then drop off by around Day 7, leaving a wound that heals naturally over four to six weeks – more than half of wounds are fully closed by Day 42 in published studies. Dogs must be given a prescribed essential medications before, during and after treatment to lower the risk of mast cell degranulation, which may occur with manipulation of a mast cell tumor and can be fatal.

What is STELFONTA?

STELFONTA is the brand name for tigilanol tiglate injection, approved by the U.S. Food and Drug Administration in November 2020 as the first intratumoral injection for Mast Cell Tumors in dogs. It is recommended for non-metastatic Mast Cell Tumors when the cancer has not spread. 

The tumors may be anywhere on the skin surface (cutaneous), and may also be under the skin if located at or below the elbow or hock, so the destroyed tumor can easily slough away.

The active ingredient works by breaking down tumor cell walls, disrupting the tumor’s blood supply, and causing the tumor tissue to detach – leaving a wound that heals without intervention, by second intention.

Who is Bruno?

Bruno is a dog living with existing health conditions who was diagnosed with Mast Cell Tumors. His owner, Berni, wanted to understand what STELFONTA treatment would look like in real life before the injection day. She sought information from world leading veterinary oncologists, spoke with her veterinarian about what to expect, and prepared her home in advance.

Berni’s account below is one owner’s real experience. Every dog is different, and STELFONTA should only be administered by a veterinarian who has assessed the individual case.

Is my dog a candidate?

STELFONTA is only for dogs with non-metastatic Mast Cell Tumors (meaning that your veterinarian has confirmed that the tumor has not spread from where it first started to other parts of your pet’s body). The veterinarian will confirm the tumor type, stage the disease, and check the tumor’s location. Subcutaneous tumors above the elbow or hock – including those on the body, head or neck – must not be injected with STELFONTA because of the risk of dead tumor tissue accumulating in the subcutaneous space and causing severe systemic reactions. Pregnant, nursing or breeding dogs, and dogs on certain concurrent medications, may not be suitable candidates.

DAY BY DAY

What treatment actually looked like

Berni’s account of Bruno’s response – from the injection at the clinic to hair growing back over the treated site.

DAY 0 

Treatment day at the clinic

Two days before his STELFONTA injection, Bruno started his essential medications to reduce the risk of mast cell degranulation.  These continued for a total of 10 days, so Berni used the free medication tracker.

Bruno did not require sedation for the injection, but some dogs are sedated to enable accurate administration.

Mast cell tumor before Stelfonta treatment

DAYS 1 – 3   

The first 72 hours

Berni had viewed other dog’s STELFONTA photos so expected swelling, bruising and discharge as the tumor destruction progressed.

While Bruno was un-phased, call your veterinarian if your dog seems in pain, is unwell, stops eating for more than a day, vomits repeatedly, has diarrhea, or shows trouble breathing. 

24 hours after Stelfonta. Tumor necrosis evident.webp

DAYS 4 – 7   

The tumor breaks down and detaches

In Bruno’s case the tumor became dark and moist before detaching. Berni had prepared her house by covering furniture, keeping easily washable items on his bed and kept a close eye on him. She found the detached tumor on the carpet, wore disposable gloves to dispose of it, then cleaned the area.

Tumor coming loose

AFTER DETACHMENT   

The wound at the treatment site

A pocket-shaped wound with healthy tissue remained once Bruno’s tumor sloughed off. Berni noticed fluid and swelling around it, which reduced gradually over the following days.

STELFONTA wounds heal by second intention – new tissue and skin grow without stitches or bandaging in most cases.

Mast cell tumor site healing

WEEKS 4 – 6+   

Healing and hair regrowth

Bruno’s site closed and hair started to grow back by 28 days after the injection. Berni confirms there are no cancerous mast cells present and the site achieved a complete response.

Timing varies with tumor size, location and the individual dog. In peer-reviewed data, more than half of wounds are fully closed by Day 42. 

Small scar where tumor was

MEDICINES TO GIVE WITH STELFONTA

STELFONTA medication schedule

Day-by-day medicine guide for the steroid, antihistamine and antacid that go with STELFONTA, based on the client information sheet. Your veterinarian will write the exact drug names and doses.

STELFONTA Concomitant Medication Table US
Corticosteroid
Starts 2 days before injection, continues 8 more days (10 days total), tapering at the end as directed.
H1 blocker
Starts on treatment day, twice daily for 8 days total.
H2 blocker
Starts on treatment day, twice daily for 8 days total.

Your veterinarian prescribes the exact drug, dose and timing. Do not skip or stop these medicines – they reduce the risk of a severe whole-body reaction from mast cells, which can be fatal. Call the clinic promptly if a dose is missed or your dog cannot keep a dose down.

Preparing your home and family

Berni’s message for other owners is simple: preparation and knowing what to expect helps. Here’s what she wishes she had known before Bruno’s treatment day.

"Everything happened exactly the way it said in the videos. Once I knew what to expect, I could handle it"
— Berni, Bruno's owner

Watch trusted treatment videos first

Seeing the expected tumor response beforehand helped Berni feel prepared when Bruno’s tumor changed color, softened, dangled and detached. Ask your veterinarian which owner videos or brochures they recommend.

Prepare your home in case of discharge from the wound

Cover sofas, dog beds, carpets and favorite resting places with washable sheets or towels. Keep disposable gloves and cleaning supplies ready. Plan for the tumor to detach on its own, potentially in an unexpected spot.

Arrange monitoring during the active period

If possible, have someone home during the first several days so your dog can be watched, taken outside more often, and checked regularly. The corticosteroid may increase thirst and urination.

Follow the medication schedule exactly

Corticosteroid starts two days before injection for 10 days total. H1 and H2 blockers start on injection day for 8 days. A pain medication may also be prescribed. Do not skip any dose – call the veterinarian for alternatives if needed.

Handle the treatment site safely

Wear disposable gloves when cleaning around the treated tumor site. Thoroughly wash any skin that comes into contact with the site, wound or discharge. Keep children and other pets away from the area until it has fully healed.

WHEN TO CALL THE VET

Contact the veterinarian promptly if you see any of these signs

Excessive pain, lameness or reluctance to move

Tiredness or collapse

Refusal to eat for more than one day

Repeated vomiting or diarrhea

Trouble breathing

Increased or excessive swelling and bruising at the site

Extensive wound formation extending beyond the treated area

Increased irritation or signs of infection

Any other sign that seems out of the ordinary

Severe systemic reactions from mast cell degranulation, including death, have been reported and are the reason the pre-treatment medications must not be skipped.

PEER-REVIEWED EVIDENCE

What the studies show

75%
Complete response after a single STELFONTA treatment

87%
Complete response after one or two treatments combined

89%
Disease-free at the treated site at 12 months

50%+
Wounds fully healed by Day 42

STELFONTA is the first and only intratumoral injection approved by the FDA for non-metastatic mast cell tumors in dogs.

Frequently asked questions

STELFONTA is a veterinarian administered intratumoral injection containing tigilanol tiglate. Once injected directly into a Mast Cell Tumor, it activates protein kinase C, breaks down tumor cell walls, disrupts the tumor’s blood supply and causes the tumor tissue to detach, leaving a wound that heals by second intention.

Yes. The FDA approved STELFONTA in November 2020 for non-metastatic cutaneous Mast Cell Tumors in dogs, and for non-metastatic subcutaneous Mast Cell Tumors located at or distal to the elbow or hock.

Non-metastatic cutaneous Mast Cell Tumors anywhere on the body, and non-metastatic subcutaneous tumors on the leg at or below the elbow or hock. Subcutaneous tumors above the elbow or hock must not be treated with STELFONTA.

No surgery is required. Sedation may be used at the veterinarian’s discretion to ensure accurate administration and patient safety.

A corticosteroid starting two days before treatment for a total of 10 days; an H1 blocker and an H2 blocker starting on treatment day for a total of eight days; and a pain medication if prescribed. These reduce the risk of severe systemic reactions from mast cell degranulation and must not be skipped.

Visible tumor change can begin within hours. In many dogs the tumor breaks down and detaches by around Day 7, although this varies with tumor size and location.

A pocket-shaped wound remains where the tumor was. It heals by second intention, with healthy new tissue and skin filling in over four to six weeks in many dogs. More than half of wounds are fully closed by Day 42 in published data.

Some dogs have developed a large wound, severe skin infection or tissue damage spreading beyond the treated area, or a severe whole-body reaction — including death. Call your veterinarian right away if you notice anything that worries you.

Cover resting areas with washable layers, stock disposable gloves and cleaning supplies, and arrange for someone to be home to monitor your dog during the active response period.

Wear disposable gloves when cleaning around the site and wash any skin that touches the site, wound or discharge. Keep children and other pets away until the site has healed.

IMPORTANT SAFETY INFORMATION

STELFONTA is available only as a veterinarian administered medication. Accidental self-injection in humans may cause severe wound formation. STELFONTA must be given together with a corticosteroid, an H1 receptor blocker and an H2 receptor blocker to reduce the risk of severe systemic reactions, including death, from mast cell degranulation. STELFONTA must not be injected into subcutaneous Mast Cell Tumors located above the elbow or hock. Treatment has been associated with cellulitis and severe tissue sloughing extending beyond the treated site.

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Bruno’s Journey

This page is provided for educational purposes for dog owners considering or undergoing STELFONTA treatment. It does not replace veterinary advice. Bruno’s story is one owner’s experience; individual responses vary. STELFONTA is a registered trademark. Full prescribing information should be reviewed with the treating veterinarian.

© 2026 · Owner story shared with permission.