What is Pheochromocytoma in Dogs?

If your veterinarian just mentioned "pheochromocytoma," you probably felt like they were speaking another language. Don't worry, you're not alone. This tongue-twister of a condition affects a tiny gland in your dog's body, but it can cause some pretty big problems. Let's break it down in a way that actually makes sense.

What Exactly Is Pheochromocytoma?

Think of your dog's adrenal glands like tiny hormone factories sitting on top of each kidney. These glands have different sections, kind of like floors in a building. Pheochromocytoma is a tumor that grows in the inner part of these glands, called the medulla.

Here's the good news and bad news rolled into one: while these tumors are technically cancer, they're genuinely rare. They account for only about 0.01 to 0.1 percent of all tumors diagnosed in dogs, and at the whole-population level they're rarer still. The first study to measure how often dogs are actually diagnosed with one, drawn from more than two million dogs in UK primary care, estimated roughly 1 case per 100,000 dogs in a single year (Litviakov et al., 2025). In plain terms, the odds of your dog ever developing this are very low.

The tumor forms in special cells that produce stress hormones, the same chemicals that kick in when your dog sees a squirrel or hears the doorbell. When a tumor develops here, it can release these hormones at random times, making your dog feel like they're constantly in "fight or flight" mode.

What Does It Look Like When Dogs Have This Condition?

The tricky thing about pheochromocytoma is that the symptoms can look like a lot of other health issues. It's like a master of disguise. Here's what you might notice:

Common signs include:

• Your dog seems tired all the time and just isn't themselves
• They're panting more than usual, even when they haven't been running around
• Their breathing seems faster than normal
• They're losing weight or won't eat their favorite foods
• In scary moments, they might even collapse

Less common but serious signs:

• Their belly looks swollen or bloated
• They seem uncomfortable when you touch their stomach
• Their legs are puffy or swollen
• They seem suddenly weak or in pain

These symptoms happen because the tumor is dumping stress hormones into your dog's bloodstream at random times. Imagine drinking five espressos when you're trying to relax. That's close to what your dog experiences.

How Do Vets Figure Out What's Going On?

Diagnosing this condition isn't as simple as a quick blood test. Your vet becomes a bit of a detective, using several tools to piece together the puzzle:

Imaging is key. Your vet will likely recommend chest X-rays and ultrasounds of your dog's belly. These help them spot any unusual masses near the adrenal glands or check if the tumor has spread to other organs like the liver, spleen, or lungs.

Sometimes vets use more advanced imaging like CT scans or MRIs to get a crystal-clear picture of what's happening inside. These tools can show if the tumor is affecting nearby blood vessels, which is important because these tumors love to invade the major blood vessels running through your dog's abdomen.

The chest X-rays are particularly helpful because they can reveal if your dog's heart has gotten bigger from working overtime to pump blood against high blood pressure, a common side effect of all those extra stress hormones floating around.

There's also a blood and urine side to the workup. Over roughly the past decade, veterinarians have gained access to tests that measure metanephrines, the breakdown products of those stress hormones, in a dog's blood or urine. A high urinary normetanephrine-to-creatinine ratio, especially alongside an adrenal mass on imaging, can strengthen the case for pheochromocytoma before surgery. A definitive diagnosis, though, still comes from examining the tumor tissue itself after it's removed.

What Can Be Done About It?

Surgery is the gold standard treatment. If caught early, removing the tumor gives your dog the best shot at a longer, healthier life. But here's the catch: surgery for this condition isn't a walk in the park.

The cardiovascular effects of those stress hormones make anesthesia riskier than usual for dogs with pheochromocytoma. Plus, these tumors tend to invade nearby tissues and sit very close to large blood vessels, which makes the surgery more complicated.

Before your dog goes under anesthesia, your vet will usually start medication at least one to two weeks beforehand to help stabilize their blood pressure and heart rate. The most common choice is phenoxybenzamine, an alpha-blocker that dampens the effect of those catecholamine surges. Whether this pre-treatment improves survival is still an open question in the veterinary literature. An influential 2008 study found that dogs given phenoxybenzamine before surgery were significantly more likely to survive the procedure (Herrera et al., 2008), but several more recent studies have not found the same survival benefit (Enright et al., 2022). Even so, many surgical teams still use it to make the period around surgery safer. Think of it like preparing a car for a long road trip, where you want everything running smoothly before you hit the road.

During surgery, the vet removes the tumor and checks the surrounding area. Sometimes if the tumor has grown into major blood vessels, they'll remove as much as safely possible to help reduce symptoms.

What if surgery isn't an option? For tumors that can't be surgically removed, there's a newer medication called toceranib phosphate that may help (Frezoulis & Harper, 2022). This drug is a tyrosine kinase inhibitor. In simple terms, it works by blocking signals that help cancer cells grow. It's also being explored as a treatment for other hormone-related tumors in dogs, including thyroid cancer and tumors affecting insulin production.

What about other treatments? Traditional chemotherapy and radiation haven't proven very effective for these tumors yet. Researchers are still studying these options, but surgery combined with medication remains the best approach.

What's the Long-Term Outlook?

Here's where timing matters most. If the cancer has already spread to other organs by the time of diagnosis, the outlook isn't great. But here's the encouraging news: dogs without metastatic disease have a good long-term prognosis. If your vet catches it early and your dog makes it through surgery successfully, they can live for years with a good quality of life.

The perioperative period, meaning those critical weeks around surgery, is when your dog needs you most. With careful monitoring and the right medication, many dogs bounce back and get to enjoy many more tail wags, belly rubs, and walks around the block.

Rare But Stay Alert Anyway

Pheochromocytoma sounds scary, and yes, it's a serious condition. But remember: it's extremely rare, and when caught early, it's treatable. The best thing you can do is stay alert to changes in your dog's behavior and health. If something seems off, even if you can't quite put your finger on what, trust your gut and call your vet.

Your dog depends on you to be their voice when they're not feeling well. And with the right care and a little luck, you can help them get back to doing what they do best: being your loyal, loving companion.

References

Enright, D., Dickerson, V. M., Grimes, J. A., Townsend, S., & Thieman Mankin, K. M. (2022). Short- and long-term survival after adrenalectomy in 53 dogs with pheochromocytomas with or without alpha-blocker therapy. Veterinary Surgery, 51(3), 438–446. https://doi.org/10.1111/vsu.13771

Frezoulis, P., & Harper, A. (2022). The role of toceranib phosphate in dogs with non-mast cell neoplasia: A systematic review. Veterinary and Comparative Oncology, 20(2), 362–371. https://doi.org/10.1111/vco.12799

Herrera, M. A., Mehl, M. L., Kass, P. H., Pascoe, P. J., Feldman, E. C., & Nelson, R. W. (2008). Predictive factors and the effect of phenoxybenzamine on outcome in dogs undergoing adrenalectomy for pheochromocytoma. Journal of Veterinary Internal Medicine, 22(6), 1333–1339. https://doi.org/10.1111/j.1939-1676.2008.0182.x

Litviakov, M., O'Neill, D. G., Brodbelt, D. C., Galac, S., & Buishand, F. O. (2025). Incidence and risk factors for phaeochromocytoma diagnosis in dogs under primary veterinary care in the UK. PLOS ONE, 20(10), e0332811. https://doi.org/10.1371/journal.pone.0332811

Vail, D. M., Thamm, D. H., & Liptak, J. M. (Eds.). (2020). Withrow and MacEwen's small animal clinical oncology (6th ed.). Elsevier.

Note: This article is for educational purposes only. Always consult with your veterinarian for proper diagnosis and treatment of any health concerns.