Dog Lumps Explained: When It’s Cancer and When It’s Not

Ideally, once you find a bump, you should try to get an appointment at your vet office as soon as possible, but if you must wait, the most important thing to remember is to remain calm until you know for sure that something is wrong. It’s very common, especially in older dogs, for bumps to show up that aren’t dangerous. 

Why Checking Your Dog’s Health is Crucial for Early Detection

It’s important to always keep up with any changes that your dog may have. You have to be responsible for taking note of any odd behaviors, new sores, or surprise bumps that appear on your dog's body, because they are not able to speak for themselves. 

For many health issues, initial symptoms in dogs are often subtle changes in personality or energy levels, and for attentive pet parents, these changes will be easy to clock. The same goes with lumps and bumps on their body. It’s important to identify any small concerns and keep an eye on them, and you should also feel free to call your vet and confirm if there are any actionable steps you need to take for your pet’s safety. 

Keeping tabs on your dog’s body is as easy as giving them one thorough full-body petting session a day. Not only does it let you look over their body for any changes or concerns, but it also acts as a bonding experience for you and your fur baby. Being able to consistently check for any changes can lead to the opportunity to treat any dangerous lumps or bumps with early treatment.

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What is a Benign Lump in Dogs?

There are many ways that a dog can develop a bump or a lump on their body that wouldn’t be cancerous, nor do they always necessitate treatment. 

Some of the most commonly diagnosed benign lumps on dogs include Lipomas or fatty tumors, cysts, papules, skin tags, histiocytomas, and even some allergic reactions. While all of these lumps can look different, and some may even look like a malignant counterpart to an untrained eye, there are some characterizations specific to each type of bump that may help you to narrow down what it could possibly be. That said, it is always best to check with your veterinarian for a true diagnosis. 

Lipoma (fatty tumors):

A mass you can feel just under your dog’s skin, usually somewhat squishy to the touch. They grow limitlessly, and can cause pain or mobility troubles depending on the location they start in if not removed. They feel very similar to malignant tumors so they need to be diagnosed by your vet.¹ 

Fibromas (skin tags):

Mostly slow-growing,  generally located in areas of increased pressure or repeat trauma, such as the elbows. While skin tags are often easily discernible based on appearance, there are some that can mimic various malignant tumors.² 

‍Histiocytomas:

These tumors commonly grow very rapidly and can become ulcerated or infected as they progress. While they grow very quickly, histiocytomas are benign. This is a very common tumor to develop in dogs younger than 3 years old, though dogs of any age can develop them. Further testing with cytology is needed to diagnose these tumors as they can appear similar to other aggressive cancers.³

Papules:

These are small bumps that appear near hair follicles and are usually due to an allergic reaction or small infection. Typically they resolve once the allergen or infection is managed without targeted treatment for the bumps themselves. Doing an allergy screening may be good for your dog if you notice some of these bumps on your pooch.⁴

Cyst: 

These bumps are formed after a hollow space is filled with either fluid or semi-fluid material. They can produce secretions and often develop in areas that are related to blocked ducts like sweat glands. They are typically removed because of their potential to become infected or uncomfortable in dogs. Some are squishy and moveable where others can feel more solid to the touch.⁴

Swelling due to allergic reaction: 

If your dog has an allergy or encounters venom such as from an insect sting (the most common cause of benign swelling in pets), it is possible that they may experience some swelling. Typically this swelling can be treated with an antihistamine like benadryl, as prescribed by a veterinarian. It makes a big difference in diagnosis if you are able to catch sight of what may have stung your dog, however it’s not always possible to know for sure, so your vet can help you identify the cause. Allergic reactions and/or bug bites should resolve in a few days, but if the lump lasts over two weeks, then these can be tumors and need to be evaluated by a veterinarian.

The main factor of benign tumors or bumps is that they are generally slow-growing. Most benign lumps will not create discomfort or pain to your dog unless it is due to the location of the growth. And often, they won’t require removal unless they are interfering with your dog’s ability to move comfortably or you notice them becoming irritated. Allergic reactions can often resolve themselves. 

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What is a Malignant Lump in Dogs?

Malignant is the medical terminology to describe something that is dangerous, and in cancer treatment it is used to describe the tumor or the cancerous cells because they are a threat to the body—regardless of whether the cancer remains localized (only lives in the place of its origin) or if it becomes systemic (spreads to other areas of the body to cause additional harm). Malignant cancer is one that has the ability to spread to other parts of the body. Essentially, being told that your dog’s lump is malignant means your dog will need treatment to manage the effects of the lump. 

Some cancers known to be associated with a malignant lump include: Mast Cell tumors, Soft Tissue Sarcomas, Mammary Tumors, Lymphoma, and Melanomas. The common traits that are noted with malignant lumps include them being fast-growing, stuck to one area (fixed location), and also that sometimes they can be ulcerated or may bleed and therefore become painful for your dog. If you find a lump on your dog and they have a strong reaction to touching it directly or the area nearby it, it’s more likely to be something doing active damage to your pet.⁵ 

If you encounter a lump that you find particularly alarming—perhaps it was the size of a dime one day and two days later the size of a quarter, or there was a similar drastic size change in a short period of time—it’s important to bring your dog to the vet as soon as you can. The doctor will take diagnostic tests to a) identify if this is a malignant growth, b) if so, determine what kind of cancer is causing it, and c) find the treatment method that your dog will need so you can make treatment decisions as quickly as possible. Many cancers are sensitive to time when it comes to starting treatment, so the sooner your dog’s lump can be diagnosed, the sooner they can start treatment, and the sooner they can get into a remission. 

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Benign vs. Malignant: How Your Vet Tells the Difference

When you find a lump or a bump on your dog it’s important to communicate with your vet about the bump. Many vets will have you send in a picture before coming into the office to get it checked out so that they are able to make a first assessment; this can help with finding the right time to schedule your dog to come in—depending on that initial diagnosis, your vet can let you know if this lump required immediate attention or not.  There are some bumps that can be somewhat more recognizable by how they look to a vet’s trained eye, and it helps to have a visual record of the size of the bump at the time that it was noticed. 

Once you get into your vet clinic, they will perform some diagnostic tests on your dog’s bump, as needed. The most common and least intrusive test will be done using a Fine Needle Aspiration (FNA) where they will take a small needle and insert it into the bump to collect some cells to look at under a microscope or be sent into a lab for testing. Some bumps may contain fluid that will be sent to a lab for identification.

Should the FNA be inconclusive in determining what the cause of the bump is, a biopsy may be required for further diagnosis. A biopsy is a minor procedure where a small portion of the lump—or if it’s small enough, the entire thing—would be removed and then sent to a lab for processing and diagnosis.

In addition, some diagnoses may benefit from additional imaging, such as with an X-ray, ultrasound, or CT scan. These additional diagnostic tests can help determine if the lump has affected any other areas of the body and if there’s any internal growth related to the external bump.

Why Appearance Isn’t Enough To Diagnose 

There are so many different ways that lumps and bumps manifest on the body, and because there are various ways that they can be expressed, there is often overlap in symptoms and signs between a malignant lump and one that is benign. 

It’s easy to be hopeful that a lump on your dog isn’t a threat to their wellbeing, but it’s important to never assume that just because one description seems to match what you’ve found on your dog, that there’s not any symptom overlap with something else. The only kinds of lumps or bumps on a dog that even a trained vet could likely diagnose with just their eyes are warts and some skin tags, and even then, it’s always recommended to have the bump tested to make sure your pet doesn't need any treatment. 

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When In Doubt, Check It Out. No Need to Panic

It is always recommended to take your pet to the vet if they are showing any kind of health concerns, including any bump or lump that you notice. A discussion with your vet, even if the bump is benign, can help you to understand how you can manage your pet’s health, and if your pooch does require treatment, your vet can offer options and walk you through the various treatment methods, taking care to highlight what may be most beneficial specifically for your dog and for you as their parent. 

But until you do know that your pet requires treatment, keep in mind that you are your dog’s health advocate, and their most trusted companion. So if you worry about them, they will know and will reflect that energy. But staying level-headed and calm—even if you find out that your pet will require veterinary care—will help to keep their stress levels down as well, which ensures a better quality of life and can aid in recovery times. 

ImpriMed helps vets develop Personalized treatment plans for dogs with canine lymphoma. Learn more here.