Fatty Growths and Dogs: The Skinny on Benign, Malignant, and Mixed Fatty Tumors

Are All Fatty Growths the Same?

Discovering a lump on a dog is one of the most common reasons pet owners seek veterinary advice, and most dogs will develop a lump at some point in their lives. Not all lumps are the same, many are benign, such as fatty tumors, but some require attention nonetheless. Many of these lumps are described as “fatty” because they originate from adipose tissue or contain fat as a major component. While the majority of fatty growths in dogs are benign and slow growing, not all behave the same way. Some are locally aggressive, some contain mixed tissue types, and a small number are malignant. Understanding the full spectrum of fat-related growths helps owners recognize why proper diagnosis is essential and why no lump should be dismissed without veterinary evaluation (Kramek et al., 1985; McChesney et al., 1980). Monitoring your pet's condition and keeping a close watch on your pet's health are important steps in ensuring the best outcome. We will also cover the importance and mediation of the emotional and physical toll a diagnosis has on the pet parent.

The information provided here is informative only; it does not constitute medical advice. Always consult a veterinarian for diagnosis and treatment.

What is a lipoma in dogs?

Fatty growths in dogs are most often benign lipomas, which are non cancerous tumors arising from fat cells or including fat as part of their structure. These benign lipomas typically develop beneath the dog's skin, particularly along the trunk or limbs, but can also occur deeper in muscle or internal organs. Lipomas are commonly found on a dog's tummy, chest, or abdomen, and can be found virtually anywhere on a dog's body where fat is present (Makovicky et al., 2020). They are characterized as usually small, hemispherical lumps that can be felt just under your dog's skin. These growths range from harmless, incidental findings to invasive cancers, and their behavior depends on the specific cell types found in the mass through pathology rather than their outward appearance (McChesney et al., 1980).

Causes and Risk Factors

The development of fatty tumors, or lipomas, in dogs is influenced by a combination of genetic and environmental factors. While the exact cause of lipomas in dogs remains unclear, certain risk factors are known to increase the likelihood of these benign tumors forming. Overweight dogs are particularly at risk (Makovicky et al., 2020). Excess fat cells in the body can contribute to the development of fatty tumors. Genetics also play a significant role, as some dog breeds like Labrador Retrievers, Cocker Spaniels, and Doberman Pinschers are more prone to developing lipomas than others. Age is another important factor. Older dogs are more likely to develop these growths (Mendes et al., 2025). Although lipomas can occur in any dog, being aware of these risk factors can help dog owners and pet parents monitor their pets more closely for any changes or new lumps.

Simple Lipomas

The most common fatty tumor in dogs is the simple lipoma, often referred to as just a lipoma. A dog's lipoma is a benign tumor composed entirely of mature fat cells and is frequently found in middle-aged to senior dogs. Lipomas in dogs are significantly more common in dogs who are at least seven years old or are considered geriatric dogs. This is the most common fatty lump and are usually slow growing. Female dogs are more likely to develop lipomas than male dogs (Mendes et al., 2025). They tend to grow slowly and feel soft, smooth, and movable under the skin. In most cases, lipomas are painless and do not affect a dog’s quality of life. Most lipomas do not require treatment and are commonly monitored unless they cause discomfort or restrict movement. Many dogs live comfortably with one or multiple lipomas for years, and treatment is often unnecessary unless a mass interferes with movement, presses on nerves, or becomes large enough to cause discomfort. Surgical removal is generally curative for simple lipomas (Kramek et al., 1985).

Infiltrative Lipomas

A less common but clinically important variant is called infiltrative lipomas. Although these tumors are still considered benign because they do not spread to distant organs, they behave more aggressively at their site of origin. Infiltrative lipomas grow into surrounding muscles, connective tissue, or fascia, making them less mobile and harder to remove completely. Their invasive nature can significantly impact a dog's ability to move, often causing discomfort and impairing mobility or gait. These tumors can lead to pain, restricted movement, or recurrence after surgery, which is why they are often managed more aggressively than simple lipomas. Infiltrative lipomas have a high recurrence rate after surgery, roughly 36% (McChesney et al., 1980; Kramek et al., 1985). Radiation therapy may be recommended as a supplementary treatment after surgery for infiltrative lipomas, especially in cases of aggressive or recurrent tumors.

Other Benign Fatty lumps

In addition to standard lipomas, several rare benign tumors originate from or include fat tissue. Angiolipomas contain both fat cells and blood vessels and may be painful due to their vascular component (Ligett et al, 2002). Fibrolipomas consist of fat mixed with fibrous connective tissue, giving them a firmer texture that can mimic more serious tumors during physical examination (Mendes et al., 2025). Myxoid lipomas contain gelatinous connective tissue alongside adipose cells and are uncommon in dogs . Pleomorphic lipomas are another rare variant characterized by unusual-looking fat cells under the microscope; despite their alarming appearance, they behave in a benign manner. Myelolipomas are benign tumors composed of fat and hematopoietic cells, and they can develop on a dog's adrenal glands, as well as the liver and spleen (Kamiie et al., 2009). Hibernomas arise from brown fat rather than white fat and are extremely rare in dogs, with little clinical significance in most cases (Piccione and Dial, 2020).

Internal Fat-Containing Tumors

Some fat-related tumors are discovered internally rather than under the skin. Myelolipomas are benign growths composed of fat and blood-forming cells and are typically found in organs such as the spleen, liver, or adrenal glands (Kamiie et al., 2009). These tumors are often detected incidentally during imaging or surgery for unrelated conditions and rarely cause clinical problems.

Malignant Fatty Tumors

While most fatty growths are benign, malignant tumors of fat tissue do occur, though they are rare. The primary malignant fatty tumor in dogs is the liposarcoma. Liposarcomas arise from fat cells but behave very differently from lipomas (Doster et al., 1986). They are often firmer, less well-defined, and more invasive, growing into surrounding tissues. Although metastasis is uncommon compared to other cancers, liposarcomas can be locally destructive and require aggressive treatment. An even rarer form, known as dedifferentiated liposarcoma, is more aggressive and difficult to diagnose, often requiring advanced pathology to distinguish it from other soft tissue sarcomas (Forlani et al., 2009).

Mixed Tumors and Fat-Containing Sarcomas

Complicating diagnosis further, some tumors contain fat without actually originating from fat cells. Certain soft tissue sarcomas may include adipose tissue as part of their structure, making them difficult to differentiate from liposarcomas without histopathology. These mixed tumors reinforce the importance of biopsy or surgical sampling for accurate classification.

Fatty Tumor Growth and Development

Fatty tumors in dogs most often grow slowly, developing beneath the dog’s skin in the fatty tissue layer. These benign lumps are typically soft, smooth, and movable, and can appear anywhere on the dog’s body, including the trunk, neck, and limbs. While most lipomas grow slowly and remain harmless, some can grow rapidly, especially in rare cases or when they become infiltrative lipomas. Infiltrative lipomas are more aggressive, invading surrounding tissues such as muscle layers and connective tissue, which can make surgical removal more complex and may affect the dog’s ability to move comfortably . Because tumors in dogs can vary in their growth patterns, regular monitoring and veterinary check-ups are essential. Tracking the size, shape, and feel of any fatty tumors helps ensure that any changes are detected early, allowing for timely intervention and the best possible outcome for your pet.

Conditions Commonly Mistaken for Fatty Tumors

Not all fat-related lumps are tumors. Lipohypertrophy refers to localized fat accumulation that occurs in overweight dogs and is not a neoplastic process (Huang et al., 2023). Fat necrosis can develop after trauma or inflammation, forming firm nodules that may be mistaken for tumors. Long-standing lipomas may also develop mineralization, becoming harder and irregular while remaining benign. These conditions often feel concerning to owners but do not carry the same implications as true tumors (Makovicky et al., 2020).

How Fatty Growths Are Diagnosed

Because fatty growths can look and feel deceptively similar, veterinarians rely on diagnostic testing rather than appearance alone. Physical examination provides useful information, but fine needle aspiration (also known as a fine needle aspirate) is commonly used to examine cells under a microscope. This procedure is performed using a small needle to collect cells from the lump. If a new lump is found on your dog, a veterinarian may recommend a fine needle aspirate to determine whether it is benign or potentially serious. When results are inconclusive or when a mass appears suspicious, biopsy and histopathology offer definitive diagnosis. A veterinary pathologist examines the tissue samples to provide a definitive diagnosis. Imaging such as ultrasound, CT, or MRI may be necessary for deep, infiltrative, or internal tumors.

Treatment options and Prognosis

Treatment depends on the type of growth, its location, and its impact on the dog’s comfort and function. Veterinary assessment is necessary for treatment options. Simple lipomas are often monitored without intervention, but it is important to monitor for changes in the size or appearance of a lipoma, especially rapid growth or leaking fluid. Lipomas generally do not shrink on their own and tend to grow slowly over time. If a new lump is noticed, or if a lump grows rapidly, becomes firm or painful, restricts movement, or begins leaking fluids, pet owners should consult a veterinarian. If a lipoma grows large enough to interfere with mobility or breathing, it should be removed and the dog should be seen promptly by a veterinarian. Dogs with large fatty tumors may struggle to find comfortable sleeping positions or experience irritation from tumors rubbing against surfaces. If a fatty tumor ruptures, it can lead to infection and should be treated by a veterinarian immediately. Rapidly growing tumors require immediate veterinary attention as this could indicate a more serious condition. Infiltrative lipomas and malignant tumors typically require surgical removal. In cases of liposarcoma, wide excision and additional therapies such as radiation may be recommended. After surgical removal, recovery time is generally seven to ten days, and post-operative care may include using a cone to prevent the dog from chewing the surgical area while it heals. Prognosis is excellent for most benign fatty tumors, while malignant tumors carry a more guarded outlook and require ongoing monitoring. Dogs develop lipomas due to a combination of genetic, age, and environmental factors, and drug interactions may also play a role.

Preventing Fatty Tumors

Although it is not possible to completely prevent fatty tumors in dogs, there are steps pet owners can take to reduce the risk of developing lipomas. Maintaining a healthy weight through a balanced diet and regular exercise is one of the most effective ways to lower the risk, as obesity is a significant factor in the formation of these tumors. Routine veterinary check-ups are also important for early detection of any new lumps or changes in existing tumors, which can make a big difference in treatment options and outcomes. Pet parents should be vigilant for signs of rapid growth, pain, or discomfort in their dog’s lipoma, and seek immediate veterinary attention if any of these symptoms occur. By focusing on a healthy lifestyle and staying alert to changes in their pet’s condition, dog owners can help support their dog’s health and well-being, even if complete prevention of fatty tumors is not possible.

While most fatty growths in dogs are harmless, they are not all the same. Accurate diagnosis is essential, as even benign tumors can cause problems depending on their location, and rare malignant tumors require prompt treatment. Regular monitoring, early evaluation of new lumps, and close communication with a veterinarian help ensure that dogs with fatty growths can continue to live healthy, comfortable lives. Lipomas shrink sometimes with proper dietary changes and supplementation.

Supplementation in Pets with Fatty Tumors

While supplements cannot cure or eliminate fatty tumors in pets, certain nutritional supplements may help support overall health, immune function, and comfort as part of a broader veterinary care plan. Omega-3 fatty acids (EPA and DHA) from fish oil are among the most commonly recommended, as they have anti-inflammatory properties that may help reduce low-grade inflammation associated with tumor growth and can support skin, joint, and cardiovascular health (Bauer, 2011). Antioxidants such as vitamin E, vitamin C, and selenium may also help mitigate oxidative stress, which is often elevated in pets with neoplastic disease, though they should be used judiciously and under veterinary guidance.

Other supplements sometimes used in pets with fatty tumors include functional mushrooms [such as maitake (Deng et al, 2009), shiitake (Chang & Wasser, 2012), turkey tail (Jeong et al.,2006) and Chaga (Lu et al., 2021)] which contain beta-glucans that can support immune modulation, particularly in pets undergoing cancer treatment. Compounds like curcumin and green tea extract are also studied for their anti-inflammatory and anti-proliferative properties, although bioavailability and dosing are important considerations (Silva et al., 2025). Importantly, supplements should never replace diagnostic testing, surgical intervention, chemotherapy, or radiation when indicated. Any supplement plan should be individualized and discussed with a veterinarian to ensure safety, avoid interactions with medications, and align expectations; especially when managing malignant tumors.

Emotional toll of a cancer diagnosis: taking care of the owner

A cancer diagnosis in a dog can feel like the ground suddenly dropping away beneath an owner’s feet. Dogs are family. They are our constant companions who offer unconditional love, routine, and emotional safety. When a veterinarian says the word “cancer,” it often triggers shock, grief, fear, and a deep sense of helplessness all at once. Many owners describe it as anticipatory loss: mourning a future that hasn’t happened yet, while still trying to stay present and strong for their dog. This emotional whiplash can be overwhelming, especially in the early days after diagnosis.

Guilt is another heavy burden many owners carry. People may replay past decisions endlessly. We may wonder if we missed symptoms, chose the wrong food, delayed a vet visit, or could have somehow prevented the disease. Even when cancer is clearly out of anyone’s control, the responsibility of being a caregiver can turn love into self-blame. These thoughts, while common, can quietly erode emotional well-being if they go unchallenged (Pavlin et al., 2020).

Managing the emotional toll begins with allowing those feelings to exist without judgment. It’s okay to be devastated, angry, numb, or confused; sometimes all in the same day. Owners often feel pressure to “stay positive,” but emotional honesty is far healthier than forced optimism. Seeking support from trusted friends, family, support groups, or even veterinary social workers can help normalize the experience and reduce isolation. Talking openly about fears does not mean giving up; it means acknowledging the reality of loving deeply.

Practical coping strategies can also help restore a sense of control. Learning about the diagnosis and treatment options at a manageable pace, keeping a notebook of questions, and focusing on the dog’s quality of life rather than worst-case scenarios can ground an owner in the present. Establishing small, meaningful routines like special walks, quality cuddle time, and favorite treats, can reinforce the bond and remind owners that love and joy still exist alongside illness (Spitnagel et al., 2025).

Caregiver burnout is a very real risk when caring for a dog with cancer. The constant vigilance, administering medications, monitoring symptoms, attending appointments, managing finances, and suppressing one’s own emotions can become physically and mentally exhausting. Many owners push themselves past their limits because they believe their dog needs them at all times, leaving little space for rest or self-care. Over time, this can lead to chronic stress, sleep problems, irritability, and emotional numbness.

Recognizing burnout is not a failure; it’s a signal that support is needed. Owners benefit from sharing caregiving responsibilities when possible, setting realistic boundaries, and giving themselves permission to rest. Even short breaks, such as asking someone else to attend an appointment or spending an hour doing something unrelated to caregiving, can help replenish emotional reserves. Self-compassion is essential as caring well for a dog also means caring for the person who loves them.

Ultimately, the emotional journey of a canine cancer diagnosis is rooted in love. While the pain is profound, so is the connection that drives owners to show up every day despite fear and exhaustion. By acknowledging grief, seeking support, and addressing caregiver burnout with kindness rather than guilt, owners can navigate this difficult chapter with greater resilience. The goal is not to eliminate sadness, but to make space for love, presence, and meaningful moments; right up to the very end.

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