What are lipomas in dogs?
Lipomas are benign (non-cancerous) fat tumors that commonly develop in older dogs, usually over 6 years old (VCAAnimal Hospitals). They form when a lump of fatty tissue begins to grow abnormally between the skin and muscle layer. Lipomas can range in size from very small, barely noticeable lumps, to quite large tumors over 4 inches wide.
Lipomas tend to grow slowly over time. The fat tumors often form on the trunk, legs, chest or abdomen, but can develop anywhere on the body (WebMD). While lipomas are typically harmless, some can interfere with mobility or become irritated if they are in areas where there is constant friction against them.
Do lipomas appear suddenly in dogs?
While lipomas can seem to develop suddenly, this is not always the case. According to Denver Veterinary Clinic, lipomas can appear to grow at varying rates in different dogs. Some may appear slowly over time, while others seem to arise rapidly.
Although lipomas often develop gradually, there is anecdotal evidence of owners noticing them overnight or over a very short period of time. So it is possible for lipomas to appear suddenly in some cases. According to PetMD, factors like trauma or inflammation may trigger rapid lipoma development. So while not all lipomas arise quickly, they can appear suddenly in some dogs.
Overall, the growth patterns of lipomas can vary substantially between individual dogs. While gradual development is perhaps more common, lipomas have the potential to develop rapidly in dogs in some cases. So it is possible for them to seem to appear suddenly, even overnight in rare instances.
What causes lipomas to form?
The exact cause of lipomas in dogs is not known. However, research suggests there may be several contributing factors.
Genetics may play a role, as certain breeds like Doberman Pinschers, Labrador Retrievers, Miniature Schnauzers, and Beagles seem more prone to developing lipomas. This suggests there could be a hereditary component.1
Lipomas are made up of fat cells, so some vets believe hormonal influences may lead to their development. An imbalance of hormones like insulin, cortisol, and growth hormone can potentially trigger lipoma formation.2
While the exact mechanisms are unknown, it seems genetics and hormones likely play a key role in many cases of lipomas in dogs.
Risk factors for developing lipomas
Certain dogs are more prone to developing lipomas than others. Some of the key risk factors include:
Overweight or obese dogs – Dogs who are overweight or obese have a much higher risk of developing lipomas. The extra fat cells in obese dogs seem to spur the formation of lipomas. Keeping your dog at a healthy weight can help prevent lipomas (source).
Age – Lipomas are most common in middle-aged and older dogs, usually first appearing between 6-9 years. The risk increases with age as cell mutations accumulate over time (source).
Breed – Certain dog breeds prone to obesity and weight gain are at higher risk for lipomas, including Labrador Retrievers, Doberman Pinschers, Mixed breeds, Miniature Schnauzers, and Beagles. The tendency seems to run in families for some breeds, suggesting a possible genetic component (source).
Signs and symptoms
The most common sign of a lipoma is a soft, movable lump under the skin. According to WebMD, lipomas are often painless benign fatty masses that form between the skin and muscle layer (1). The lumps are soft and feel doughy or rubbery to the touch. Lipomas tend to be oval or round in shape.
Though generally painless, lipomas can sometimes cause discomfort depending on their size and location (2). Large lipomas in areas like the armpit or groin can rub and irritate the surrounding skin. Lipomas around joints may restrict mobility. Signs your dog is uncomfortable include licking, nibbling, or scratching at the lump.
Lipomas usually grow slowly over time. Multiple lipomas may develop. See your veterinarian if you notice any new lumps on your dog’s body. Rapid growth or changes in an existing lipoma could indicate a problem.
Diagnosing sudden-onset lipomas
If you notice a new lump on your dog, it’s important to have your vet examine it to confirm it is a lipoma and rule out other types of lumps or tumors. According to PetMD, “Your veterinarian may recommend a noninvasive test known as a fine-needle aspirate and cytology exam.”
To diagnose a lipoma, the vet will likely perform a fine needle aspirate or biopsy of the lump. As Toe Grips explains, “Your dog needs a fine needle aspiration or biopsy of the lump to be able to definitively diagnose it as a lipoma.” This involves inserting a needle into the lump to draw out cells for examination under a microscope.
The vet may also recommend bloodwork to check for any underlying issues that could be causing lipomas to develop. Though benign, the appearance of multiple sudden lipomas could indicate an underlying health condition.
Treatment options
Most lipomas in dogs do not require any treatment. Since they are usually benign fatty masses, lipomas generally do not cause any issues and can be left alone. Some dog owners choose to monitor the size of lipomas at home and only seek treatment if the lipomas continue growing rapidly, become bothersome for the dog, or impede movement.
For problematic lipomas, there are a few treatment options:
Steroid Injection: Injecting a steroid like dexamethasone directly into the lipoma can help shrink the size of the mass. However, results are temporary and lipomas often regrow over time. According to PetMD, steroid injections are most useful for treating lipomas that are in sensitive areas like the armpit or groin where surgical removal may be more difficult.
Surgery: Surgically removing lipomas is considered the most effective treatment option. Surgery provides full removal of the fatty mass and minimizes chances of regrowth. Surgery may be recommended for fast growing lipomas, large lipomas, or lipomas that are impacting movement or quality of life. More invasive lipoma removal procedures may require general anesthesia.
Preventing lipomas
While there’s no foolproof way to prevent lipomas from forming, there are some steps dog owners can take to reduce the chances:
Maintain a healthy weight. Overweight and obese dogs are more prone to developing fatty lipomas, so keeping your dog at an optimal weight can help prevent them. Feeding measured meals, avoiding table scraps, and ensuring adequate exercise can all support weight management.
Feed a well-balanced diet. Some research indicates that diets too high in carbohydrates may contribute to lipoma development. Choosing a high quality dog food with moderate fat, high protein, and low carbohydrates may be beneficial.
Get regular exercise. Keeping your dog active supports weight control and overall health, which may help prevent lipomas. Aim for 30-60 minutes of exercise per day based on your dog’s age and condition.
Have regular veterinary checkups. Your vet can monitor your dog’s weight, diet, and overall health. Annual exams and bloodwork can also help detect any underlying issues early on.
While no prevention method is guaranteed, following these tips can promote your dog’s health and may help reduce lipoma risk.
Lipoma recurrence
One concern with surgically removing lipomas is the chance of recurrence. According to research, lipomas can recur after removal, especially if the excision was incomplete [1]. Infiltrative lipomas in particular have a high recurrence rate, ranging from 36-50% [2]. This is much higher than the recurrence rate for simple lipomas, which is less than 2% [2].
The recurrence of infiltrative lipomas often happens within 8 months after surgery [1]. Therefore, it’s important to monitor the surgery site closely during this time. Any signs of recurrence should prompt a veterinary visit. Catching a recurring lipoma early allows for quicker treatment before it has a chance to grow extensively.
While surgical excision carries a risk of recurrence, it still provides the best chance to remove the lipoma. Performing a complete excision when possible helps lower the chances of the lipoma growing back. Regardless, pet owners should know there is a possibility of dealing with recurrent lipomas and continue checking the surgery site long-term.
When to see the vet
If your dog develops any new lumps or bumps, it’s a good idea to have your veterinarian take a look, especially if the lump seems to appear suddenly or grows rapidly. Here are some key signs that warrant making an appointment with your vet:
- Appearance of any new, rapidly growing lumps or bumps on your dog’s body. Even if the lump looks like a benign fatty tumor, rapid changes in size can indicate a more serious issue that requires diagnosis. Your vet can determine if biopsy or removal is needed (1).
- A lump that interferes with your dog’s movement, range of motion, or quality of life. Lipomas that form near joints or on the legs/paws can make movement difficult or painful (2).
- Any lump that shows signs of irritation, redness, ulceration or oozing. These symptoms suggest inflammation or irritation that should be evaluated by your vet (3).
While most lipomas are harmless, it’s important to monitor all lumps and bumps closely. Schedule an exam with your vet promptly if a new lump appears or an existing one changes or causes discomfort. Getting an accurate diagnosis and appropriate treatment will help ensure your dog’s health and comfort.
(1) https://www.denvervet.com/site/blog/2022/08/31/fatty-tumor-lipoma-dog
(2) https://toegrips.com/lipoma-in-dogs/
(3) https://vcahospitals.com/know-your-pet/adipose-lipoma-tumors
