How Fast Do Fatty Tumors Grow On Dogs?

Fatty tumors, also known as lipomas, are benign lumps of fat that can develop under a dog’s skin. They are one of the most common types of tumors found in dogs, especially in middle-aged and senior dogs (source). While often harmless, fatty tumors can sometimes grow large enough to interfere with movement or cause discomfort. Understanding the typical growth rate for fatty tumors is important, as it can help dog owners determine when a tumor may become problematic and require veterinary attention.

This article provides an overview of how quickly fatty tumors generally grow in dogs. It is intended to help dog owners understand what to expect with these common growths, and how to monitor changes that may indicate a need for veterinary assessment.

What Are Fatty Tumors?

Lipomas are benign fat cell growths that develop under a dog’s skin. According to the Mayo Clinic, lipomas are the most common noncancerous soft tissue growth found in dogs. They are usually slow-growing, soft, moveable lumps made up of fat cells that form between the skin and muscle layer (

Lipomas are typically harmless, though they can occasionally become problematic depending on their size and location. They often grow slowly over months or years and can develop anywhere on a dog’s body where fat is stored. Common locations include the chest, abdomen, upper legs and armpits. Lipomas are usually painless, smooth, and soft to the touch.

Typical Growth Rate

Fatty tumors tend to grow very slowly, often at an imperceptible rate. In many cases, fatty tumors may remain stationary and show no noticeable growth for years. When fatty tumors do enlarge, the typical growth rate is gradual, averaging around 1-2 millimeters per month according to veterinary sources.

Due to the slow pace of enlargement, fatty tumors can take many years to become readily apparent or bothersome. Owners may not notice small fatty tumors until they have been present for quite some time and have had a chance to expand to a more visible or palpable size. The slow growth means they are often dismissed at first or confused with other benign masses.

According to veterinary research, the typical growth pattern for a fatty tumor starts with a long latent or stationary phase, followed by a period of relatively steady enlargement over months to years. However, the growth rate can vary dramatically between different tumors and dogs [1].

Factors Affecting Growth

There are several key factors that impact the growth rate of fatty tumors in dogs:

Age of the dog – Older dogs tend to develop fatty tumors at a higher rate than younger dogs. The tumors tend to grow slower in younger dogs.

Overall health – Dogs that are overweight or have other health conditions may experience faster fatty tumor growth. Tumors grow slower in dogs that are at a healthy weight and activity level [1].

Tumor location – Fatty tumors located in areas with abundant fat cells, like the torso, may grow larger than tumors on the legs or head. Pressure and irritation can also impact growth.

Tumor size at discovery – The larger the fatty tumor is when first found, the faster it is likely to grow. Small tumors tend to have a slower growth rate.

Monitoring Changes

It’s important to monitor fatty tumors and track any changes in their size or appearance. Here are some tips:

Take photos of the tumors periodically, such as every few months, for size comparison. Make sure to take the photos from the same angle and distance each time. You can place a coin next to the tumor for scale. Photos allow you to visually inspect if the tumor is increasing in size over time.

Measure the tumor’s dimensions with calipers when you first notice it and every few months thereafter. Record the length, width, and height. An increase in measurements could indicate faster growth. Measure other existing fatty tumors at the same intervals for comparison.

Check your dog’s body thoroughly on a regular basis to look for any new tumors. Run your hands along their torso, chest, legs, and other common areas where lipomas develop. Finding a new tumor early allows for closer monitoring.

Notify your vet promptly about any tumors that are rapidly increasing in size, shape, or firmness, as these may require surgical removal. Routine monitoring helps provide your vet with helpful information to determine the best course of treatment.

When to Visit the Vet

While many fatty tumors are benign, there are some warning signs that indicate it’s time to take your dog to the vet for an evaluation. According to, you should make an appointment if you notice any of the following:

  • Sudden rapid growth – A fatty tumor that quickly gets much larger may indicate a problem. Benign lipomas tend to grow slowly over months or years.
  • Interference with movement – Fatty tumors in areas like the legs, shoulders or neck can make it difficult for a dog to move or walk normally. This requires prompt veterinary attention.
  • Ulceration – If the surface of the fatty tumor opens up, it can allow infection to develop and cause discomfort. Ulcers need to be evaluated and treated.
  • Pain or inflammation – Fatty tumors are typically not painful. If the lump becomes warm, inflamed or seems to hurt your dog, it may be something more serious like liposarcoma.

According to, rapid changes in fatty tumors often warrant biopsy or surgical removal. Your vet can determine the best course of action if your dog’s lipoma exhibits any concerning signs.

Diagnostic Tests

A veterinarian will first perform a physical exam of your dog to locate and feel any fatty lumps under the skin. The vet will note the location, size, shape and texture of the mass. Most lipomas have a soft, mobile, and non-painful feel on palpation. According to PetMD, lipomas feel like a soft bubble under the skin and can be moved around slightly [1].

The next diagnostic step is often a fine needle aspiration. This involves inserting a small needle into the fatty tumor and suctioning out some cells. These cells can then be examined under a microscope to confirm it is a benign lipoma [2]. According to VCA Hospitals, most lipomas can be definitively diagnosed using a fine needle aspiration [3].

If the diagnosis remains unclear after a physical exam and fine needle aspiration, your vet may recommend a biopsy. This involves surgically removing all or part of the fatty tumor so the cells can be examined. A biopsy provides a more definitive diagnosis.

Advanced imaging such as an ultrasound, CT scan or MRI may also be used to evaluate the size, location and internal structure of a suspected lipoma. These tests help distinguish lipomas from other types of tumors [1].


Treatment Options

There are several options for treating fatty tumors in dogs:

Observation: Some veterinarians may recommend simply monitoring the tumor over time instead of immediate removal, especially if the lipoma is small and not impacting the dog’s mobility or quality of life. The tumor will be checked periodically at vet appointments to watch for any changes.

Surgery: Surgical removal is often the most effective treatment, especially for large or problematic lipomas. The surgery is minimally invasive and involves making a small incision to remove the entire tumor. It’s ideal to remove lipomas when they are still small.

Liposuction: In some cases vets may use liposuction techniques to remove the fatty tumor. This is less invasive than surgery but may not remove the entire growth.

Medication: If a biopsy reveals the fatty tumor is actually a liposarcoma (cancerous), chemotherapy medications or other drugs may be used to try to shrink the tumor or slow its growth.


While fatty tumors cannot be entirely prevented in dogs, there are some steps owners can take to promote early detection and slow their growth. According to Embrace Pet Insurance, there is no known way to prevent lipomas from developing. However, maintaining a healthy weight and providing excellent nutrition may help reduce risk factors.

Overweight and obese dogs tend to develop fatty tumors more frequently. Keeping your dog at a healthy weight through proper diet and exercise can help avoid excessive fat deposits under the skin where lipomas often form. Provide a nutritious, high-quality diet and avoid overfeeding treats and table scraps.

Regular grooming and hands-on body checks can help detect lipomas early when they are small and easier to manage or remove. Monitoring for any new lumps or bumps will allow you to have them assessed promptly by your veterinarian. Early intervention gives more options for nonsurgical reduction or removal.

While lipomas can’t always be prevented in dogs, diligent monitoring and proactive health maintenance create the best opportunity for minimal impact. Discuss any concerns over new lumps or growths with your veterinarian right away.


To conclude, fatty tumors on dogs can grow slowly, usually over a period of months or years. However, occasionally some fatty tumors can grow rapidly. Key factors that influence the growth rate include the location of the tumor, with tumors on legs and around joints often growing faster. The breed and age of the dog also impacts growth rate.

It’s important to monitor fatty tumors closely and watch for any changes in size, shape, color or texture. Rapid enlargement, ulceration, inflammation or pain can all be signs of concern. Schedule regular vet checkups for fatty tumors and immediately visit the vet if you notice any unusual changes.

While not all fatty tumors require treatment, surgical removal and biopsy may be recommended for faster growing tumors or ones causing discomfort. With close monitoring and vet care, the prognosis for benign fatty tumors is often excellent.

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