Dog Tumor Guide: Differentiating Cysts from Lipomas

Lumps can appear anywhere on a dog's body, making it important to regularly check for any unusual growths. Your mind may immediately jump to worst-case scenarios, but the truth is that not all masses in dogs are malignant (many lumps are benign). However, some may be cancerous lumps and require veterinary assessment. Two of the most common types of benign lumps are cysts and lipomas. While both are usually harmless, they are not the same. Understanding the difference can help you make better decisions about your dog’s health.

In this guide, we’ll break down what cysts and lipomas are, how to tell them apart, and when it’s time to visit the vet, highlighting the crucial role of veterinary medicine in diagnosing and managing lumps in dogs.

Introduction to Benign Tumors

Benign tumors are non-cancerous growths that commonly appear on a dog’s skin, often causing concern for pet parents when first discovered. Unlike cancerous growths, benign tumors such as lipomas and sebaceous cysts are typically slow-growing and do not invade other tissues or spread throughout the body. These lumps can develop on various parts of the skin surface and are usually composed of fat cells or other non-cancerous cell types. While most benign tumors are harmless, they can sometimes become large enough to cause discomfort or interfere with your dog’s movement, especially if located in sensitive areas. For this reason, it’s important for pet parents to monitor any new or existing lumps and consult with a veterinarian if changes occur. Regular veterinary check ups help ensure that benign tumors are managed appropriately and that any suspicious changes are addressed promptly (Kim et al., 2022).

What Is a Cyst?

A cyst is a sac-like structure under the skin that is typically filled with fluid, pus, or a thick, cheese-like material. In dogs, the most common type is a sebaceous cyst, which forms when a hair follicle or sebaceous gland becomes blocked, filling with skin oil, dead cells, or keratin. Cysts are a type of harmless cyst, generally benign, and do not spread to other parts of the body.

Both lipomas and cysts require a veterinary fine needle aspirate (FNA) for definitive diagnosis.

Common characteristics of cysts

They are usually round and well-defined, can feel firm or slightly soft, may have a small opening or “pore” at the surface, can grow slowly over time, and sometimes rupture and leak material. Cysts can appear anywhere on a dog’s body but are commonly found on the back, neck, or torso.

What causes sebaceous cysts?

Cysts often develop due to blocked oil glands, skin trauma or irritation, genetic predisposition, and infections. Some breeds are more prone to cysts, especially those with thick or oily coats.

Types of Dog Cysts

Cysts can develop in various forms on a dog’s skin, each with its own unique characteristics and causes. Skin tags are another type of benign skin growth that can appear similar to cysts, often forming in areas where the skin rubs together. Understanding the different types can help pet parents recognize what they’re seeing and know when to seek veterinary advice.

Follicular cysts

They are among the most common, forming when hair follicles become blocked or damaged. These cysts often appear as small, round, fluid-filled bumps just beneath the skin’s surface. They may be blueish or flesh-colored and can sometimes rupture, releasing a thick, whitish material (Adedeji et al., 2017).

Sebaceous cysts

They develop from the oil glands (sebaceous glands) in the skin. When these oil glands or their ducts become clogged, a firm, raised lump can form. Sebaceous cysts are usually slow-growing and may have a visible pore at the center. If they rupture, they can leak an oily or cheesy substance and may become inflamed or infected (Duclos et al.,2008).

Dermoid cysts

These are less common but can occur in some dog breeds. These cysts originate from skin cells and may contain hair, oil, or even skin tissue. Dermoid cysts are typically firm and may be present from birth, often found along the spine or head.

While most cysts are benign and not a cause for alarm, any new or changing lump on your dog’s skin should be evaluated by a veterinarian. Early identification and treatment can help prevent complications, especially if the cyst becomes infected or causes discomfort.

What Is a Lipoma?

A lipoma is a benign (non-cancerous) tumor made up of fatty tissue, consisting of fat cells. Lipomas can develop anywhere on a dog's body, but are most commonly found on the trunk and legs, and are especially prevalent in older or overweight dogs. While lipomas are generally harmless, it is important to monitor them, as they can sometimes transform into malignant tumors called liposarcomas if not properly observed (O'Neill et al., 2018).

Common characteristics of lipomas (fatty lumps):

They are most ofter soft and squishy to the touch, easily movable under the skin, usually painless and

slow-growing and are found just under the skin. Lipomas are most often seen in middle-aged to older dogs, particularly those who are overweight.

Where do lipomas appear?

They are commonly found on the chest, abdomen and legs (especially upper limbs). Some dogs develop multiple lipomas over time. Certain breeds, such as miniature schnauzers, are more prone to developing lipomas and should be checked regularly for new lumps.

Types of Lipomas in Dogs

Lipomas are the most common benign tumors found in dogs, especially as they age or if they are overweight. Some types of lipomas or related tumors may be more common in male dogs. While most lipomas are harmless, there are several types, each with distinct features that pet parents should be aware of.

Simple lipomas

These are the classic fatty lumps that many pet parents notice on their dog’s body. These are soft, easily movable, and usually painless. They consist entirely of fat cells and rarely cause problems unless they grow very large or are located in an area that interferes with movement.

Infiltrative lipomas

These are less common but more concerning. Unlike simple lipomas, infiltrative lipomas can invade surrounding tissues such as muscles or connective tissue, and surrounding tissue, making surgical removal more challenging. These fatty tumors may require advanced diagnostics and more extensive surgery to achieve complete removal.

Angiolipomas

They are a rare type of lipoma that contain both fat cells and blood vessels. They may appear as firmer, sometimes bluish bumps under the skin. While still considered benign, their vascular nature can make them more prone to bruising or bleeding.

Spindle cell lipomas

These are another rare variant, characterized by the presence of spindle-shaped cells mixed with fat cells. These lumps are usually firm and may be mistaken for other types of skin tumors, so a definitive diagnosis often requires fine needle aspiration or biopsy.

Because not all lumps and bumps are benign tumors, it’s essential for pet parents to monitor their dog’s skin regularly. If you notice a new lump, a change in an existing lump, or any signs of discomfort, consult your veterinarian. Vets diagnose lumps using fine needle aspiration or biopsy to distinguish between benign fatty tumors, dog cysts, and more serious malignant tumors. In some cases, surgical removal may be recommended, especially if the lump is growing, causing discomfort, or its nature is uncertain. Regular veterinary check-ups and prompt attention to skin changes are key to keeping your furry family member healthy and comfortable.

Key Differences Between Cysts and Lipomas (The most common lumps and bumps)

While both cysts and lipomas can feel like lumps under the skin, there are some important differences. Skin lumps and skin bumps are common in dogs, and any unknown lump should be evaluated by a veterinarian to determine whether it is benign or malignant. Any new lump or bump on your dog that persists beyond a few days or is growing in size should be checked by your veterinarian. Regular full-body checks for lumps on your dog are essential, as lumps can appear in unexpected or hidden places (Volta et al., 2006).

Texture

• Cysts: Firmer and may feel like they contain fluid or thick material

• Lipomas: Soft, doughy, and squishy

Movement

• Cysts: May be somewhat movable but often feel more attached

• Lipomas: Freely movable under the skin

Contents

• Cysts: Filled with fluid, pus, or keratin

• Lipomas: Made of fat tissue

Risk of Rupture

• Cysts: Can rupture and leak, sometimes becoming infected

• Lipomas: Do not rupture

Appearance

• Cysts: May have a visible pore or become inflamed

• Lipomas: Usually smooth under normal skin

Are Cysts or Lipomas Dangerous?

In most cases, both cysts and lipomas are benign growths or benign lumps and not life-threatening. However, some lumps may be cancerous lumps or cancerous growths, which can be more serious. Early detection is especially important for aggressive cancers to improve treatment outcomes. Some cancers can present as both skin and internal tumors, which may influence treatment decisions and options. Surgical removal is often the recommended treatment for tumors that are cancerous or causing discomfort to the dog, while benign tumors like lipomas may not require treatment unless they interfere with movement or cause discomfort. However, that doesn’t mean they should be ignored (Maddens & Takeaways, 2026).

When cysts can become a problem:

• If they rupture and become infected

• If they grow rapidly

• If they cause discomfort

When lipomas can become a problem:

• If they grow large enough to interfere with movement

• If they press on nerves or organs

• If they are actually a more serious type of tumor (rare but possible)

There is also a more invasive form called an infiltrative lipoma, which can grow into surrounding tissues and may require surgical removal.

How Are They Diagnosed?

Even though cysts and lipomas have typical characteristics, it is impossible to diagnose a lump with certainty just by touching it. A physical examination is the first step in diagnosing a lump, followed by further diagnostic procedures. One common method is a fine needle aspirate, which allows the veterinarian to collect cell samples from the lump to help determine its nature.

Veterinarians usually use additional diagnostic methods, and sometimes the entire mass is surgically removed for further analysis to ensure an accurate diagnosis. Biopsies and treatments may also be used to identify and target tumor cells, especially if there is concern about malignancy or spread.

Never attempt to pop or squeeze a lump, as it can cause severe infection or other complications.

Fine Needle Aspiration (FNA)

A small needle is used to collect cells from the lump. This is quick, minimally invasive, and often provides immediate answers.

Biopsy

In some cases, a tissue sample is sent to a lab for detailed analysis. For small or easily accessible lumps, your veterinarian may use local anesthesia during the biopsy to minimize discomfort.

Imaging (if needed)

X-rays or ultrasounds may be used if the lump is deep or unusual.

Should You Remove a Cyst or Lipoma?

Not all lumps need to be removed. The decision depends on several factors. Early intervention and appropriate removal can lead to successful treatment and better outcomes for your dog.

Removal Recommendations

When the lump is growing quickly, it causes pain or discomfort, it interferes with movement, it becomes infected (in the case of cysts), or there is uncertainty about the diagnosis, removal may be the best course of action.

When Monitoring is Recommended

If the lump is small and not changing, it is confirmed to be benign and it does not affect your dog’s quality of life, your vet may recommend measuring the lump regularly to track any changes.

Can You Prevent Cysts or Lipomas?

There’s no guaranteed way to prevent either condition, but some steps may reduce risk. Overweight dogs are at higher risk for developing lipomas, so maintaining a healthy weight is important. Additionally, supporting healthy skin through proper diet and regular grooming can help promote overall well-being and may reduce the risk of cysts (Tenekeci et al., 2024).

For cysts:

• Keep your dog’s skin clean and healthy

• Groom regularly to prevent clogged follicles

• Address skin infections promptly

For lipomas:

• Maintain a healthy weight

• Provide regular exercise

• Feed a balanced diet

Obesity is strongly linked to the development of lipomas, so weight management is especially important.

Supplementation with functional mushrooms and Omega fatty acids, can also be beneficial for both conditions.

The Importance of Early Detection

Early detection of lumps and bumps on your dog’s skin is essential for identifying potential health concerns before they become serious. Pet parents should make it a habit to regularly check their dog’s body for any new or changing growths, as some lumps may be benign while others could be malignant tumors like mast cell tumors or squamous cell carcinoma. By catching lumps and bumps early, pet parents can help prevent the spread of cancerous cells and improve the chances of a positive outcome for their furry family member.

When Should You See a Vet?

You should always have a new lump checked by a veterinarian, but some signs make it more urgent:

• Rapid growth

• Pain or sensitivity

• Redness or swelling

• Discharge or bleeding

• Changes in shape or texture

• Difficulty walking or moving

• Warning signs such as rapid growth, dog pain, bleeding, or if the lump feels hot

If your dog shows signs of pain or discomfort (dog pain), you should seek veterinary attention immediately.

A good rule of thumb: any new lump or bump should be evaluated, even if it seems harmless.

Monitoring Lumps on your Dog's skin

Keeping track of your dog’s lumps can help catch changes early. It’s important to regularly inspect your dog’s entire body and dog’s skin, as lumps, cysts, or growths can appear in unexpected places, including less obvious areas. Lumps can also appear on the dog's head and should be checked during regular inspections.

Differentiating Benign Growths from Malignant Tumors

Finding a lump on your dog can be stressful, but not all lumps are dangerous. Cysts and lipomas are among the most common and benign types of growths in dogs.

There are many other types of growths and tumors in dogs, each with unique characteristics. Basal cell carcinomas, for example, rarely spread to other organs. Squamous cell carcinoma risk increases with sun exposure, especially in light-coated breeds. Spaying a female dog before her first heat cycle significantly reduces the risk of developing mammary masses, which can be either benign or malignant. Oral tumors, including oral melanoma, can develop in the mouth or even in the nail bed, while epulis arises from the gum tissue surrounding the teeth. Mast cell tumors, the most common malignant tumors in dogs, can cause allergic reactions due to histamine release, especially if manipulated. The immune system plays a role in resolving some growths, such as papillomas and histiocytomas, particularly in young dogs. Papillomas are viral, wart-like growths often found around the mouth of young dogs and may resolve as the immune system matures. Histiocytomas are benign skin growths that usually occur in dogs less than 2 years old, often on the head or legs, and typically regress spontaneously.

If you notice a lump on your dog, don’t panic, but don’t ignore it either. Differentiating between malignant tumors and benign ones is of utmost importance. A quick check by your vet can give you peace of mind and ensure your dog stays healthy and comfortable.

References

Adedeji, A. O., Affolter, V. K., & Christopher, M. M. (2017). Cytologic features of cutaneous follicular tumors and cysts in dogs. Veterinary Clinical Pathology, 46(1), 143-150.

Duclos, D. D., Hargis, A. M., & Hanley, P. W. (2008). Pathogenesis of canine interdigital palmar and plantar comedones and follicular cysts, and their response to laser surgery. Veterinary Dermatology, 19(3), 134-141.

Kim, D., Dobromylskyj, M. J., O'Neill, D., & Smith, K. C. (2022). Skin masses in dogs under one year of age. Journal of Small Animal Practice, 63(1), 10-15.

Maddens, E., & Takeaways, K. (2026). Dog Skin Lumps and Bumps: Types, Causes & When to Worry. Veterinary Dermatology.

O’Neill, D. G., Corah, C. H., Church, D. B., Brodbelt, D. C., & Rutherford, L. (2018). Lipoma in dogs under primary veterinary care in the UK: prevalence and breed associations. Canine Genetics and Epidemiology, 5(1), 9.

Tenekeci, G. Y., Tunç, A. S., & Demirtaş, O. B. (2024). Pathomorphological approach on canine sebaceous tumors. Mediterranean Veterinary Journal, 9(3), 403-409.

Volta, A., Bonazzi, M., Gnudi, G., Gazzola, M., & Bertoni, G. (2006). Ultrasonographic features of canine lipomas. Veterinary Radiology & Ultrasound, 47(6), 589-591.