Dog Tumors vs. cysts: identification, differences, and care

June 17, 2024 - 5 min read

The information in this article has been reviewed by Dr. Rebecca MacMillan on June 14, 2024 . Although it may provide helpful guidance, it should not be substituted for professional veterinary advice.

A drawing of a dog's foot with a circled area highlighting a red, inflamed spot on the heel

While cysts and tumors in dogs are distinct conditions, both can present serious health challenges. By understanding the differences between them — and the specifics of each — and you can make informed decisions about your pup’s care. 

With early detection and appropriate treatment, you and your vet can prevent or mitigate serious health complications, helping your dog stay happy and healthy as long as possible.

Understanding tumors in dogs

Understanding potential causes, signs, and treatment options can help dog parents care for a dog with a tumor.

adult Cocker Spaniel dog lying on warm floor indoors

What is a tumor in dogs?

Just like in humans, a tumor is an abnormal mass of tissue that forms on your dog when cells grow and divide more than they should, or do not die when they should. Tumors can develop in any part of the body and vary in their behavior. They’re classified into two main types: 

  • Benign tumors: Non-cancerous tumors that don’t spread to other parts of the body, though they can still grow large enough to cause health problems.

  • Malignant tumors: Cancerous tumors that can invade nearby tissues and spread to other areas of the body like the lymph nodes and lungs, making them more dangerous.

What does a tumor look like on a dog?

Tumors on dogs can have various appearances depending on their type and location. They may present as lumps or masses on or under the skin and can be firm or soft to the touch. Tumors can range in size from tiny nodules to large, noticeable growths. The surface of the tumor can be smooth or it might be  irregular, and some dog tumors may bleed, become ulcerated, or start oozing fluid. 

A dog at the vet

Common tumor types

  • Lipomas: Benign, fatty tumors that are usually soft, movable, and found under the skin. Common in older dogs, lipomas are typically harmless but can become large and uncomfortable.

  • Mast cell tumors: Malignant tumors that can appear in various forms, often as raised, red, and sometimes ulcerated lumps. They’re known for their unpredictable behavior and potential to release histamines causing allergic reactions.

  • Fibrosarcomas: Malignant tumors originating from fibrous connective tissue. These tumors are usually firm, fast-growing, and can be invasive, often requiring aggressive treatment.

  • Histiocytomas: Benign tumors that often appear as small, button-like lumps which may or may not be inflamed. These are classically found on young dogs. They usually resolve on their own without treatment.

  • Melanomas: Skin tumors arising from pigment-producing cells, which can be benign or malignant. Malignant melanomas are more commonly found in the mouth or on the digits and can be aggressive.

Causes of tumors in dogs

The development of tumors in dogs can be influenced by various factors, including genetics, environmental exposures, and age. Some breeds have a genetic predisposition to certain types of tumors. Environmental factors such as exposure to toxins, chemicals, and sunburns/ultraviolet radiation can also play a role. The risk of developing tumors increases with age, as the body’s ability to regulate cell growth and repair diminishes over time.


Symptoms of tumors in dogs can vary widely depending on type and location. Common signs include:

  • Visible lumps or masses on or under the skin

  • Changes in size, shape, or color of existing lumps

  • Unexplained weight loss or loss of appetite

  • Lethargy or decreased activity levels

  • Difficulty breathing, eating, or moving, depending on the tumor’s location

  • Persistent sores or wounds that do not heal

  • Bleeding or discharge from any part of the body

Early detection and prompt veterinary evaluation of any new or changing lumps might help improve your dog’s prognosis. 

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Understanding cysts in dogs

While cysts and tumors are different, cysts can still pose significant medical challenges for dogs. Identifying and understanding cysts can help you seek the appropriate care and treatment.

What is a cyst in dogs?

A cyst is a sac-like structure that can contain fluid or semi-solid material. Cysts are typically benign and can form on or under the skin. Unlike tumors, which involve abnormal cell growth, cysts are often the result of blocked glands or ducts, infections, or other skin conditions. While generally harmless, cysts can sometimes cause discomfort or become infected.

What does a cyst look like on a dog?

Cysts on dogs usually appear as smooth, round lumps under the skin. They can range in size from very small to several centimeters in diameter. The surface of a cyst on a dog is typically smooth, and it may feel firm or fluctuant (soft and compressible) to the touch. Cysts are often not painful unless they become infected or rupture.

Common cyst types

Some common types of dog cysts:

  • Sebaceous cysts: Formed when a sebaceous gland becomes blocked and fills with sebum, a greasy substance. These cysts are usually small and slow-growing.

  • Follicular cysts: Occur when a hair follicle becomes blocked, leading to the formation of a fluid-filled sac. These cysts can sometimes rupture and release their contents.

  • Dermoid cysts: Rare congenital cysts that contain hair, skin, and other tissues. They can be present at birth or develop later in life.

  • Apocrine sweat gland cysts: Form in the sweat glands and can appear as small, clear or bluish lumps under the skin.

  • Interdigital cysts - Swellings between the digits (toes) usually as a result of chronic inflammation. They are often seen in overweight dogs or those with underlying skin allergies.

A Golden Retriever sitting on a patterned rug, looking up with a curious expression.

Causes of cysts in dogs

Cysts in dogs can develop due to several reasons, including blocked glands or hair follicles, trauma to the skin, or genetic predispositions. Infections and inflammatory skin conditions can also lead to cyst formation. Some breeds are more prone to developing certain types of cysts.


Common symptoms of cysts in dogs include:

  • Smooth, round lumps under the skin

  • Discharge from the cyst if it ruptures

  • Redness or inflammation if the cyst becomes infected

  • Discomfort or pain if the cyst is in a sensitive area or becomes large

Regular monitoring and veterinary check-ups can help reduce significant discomfort or complications for your dog.

Key differences between tumors and cysts

While it’s crucial for a veterinarian to make the ultimate diagnosis, understanding the major differences between tumors and cysts in dogs may help pet owners recognize potential issues early and seek timely professional care.

Dog cyst vs. tumor: physical characteristics and growth patterns

Here’s a comparison of their physical characteristics, growth patterns, and potential for harm:

Feature Tumors Cysts
Physical characteristics Hard or soft, often irregularly shaped, may change over time Smooth, round, may contain fluid or semi-solid material
Growth patterns Can grow rapidly, may spread (malignant tumors) Typically grow slowly, do not spread
Potential for Harm Malignant tumors can be life-threatening Usually benign, less harmful, can cause discomfort if infected or ruptured

Diagnosing tumors and cysts in dogs

Ultimately, only a veterinarian can diagnose tumors and cysts in dogs. But having knowledge about these conditions can help you recognize early signs, seek timely medical advice, and make informed decisions about your pet’s care.

Veterinary examination

The first step in diagnosing tumors and cysts in dogs is a thorough veterinary examination. Your vet will take a detailed medical history, then evaluate the size, shape, texture, and location of the growth. They’re also likely to ask about any changes in its appearance or your dog's behavior

X-ray film of dog lateral view with red highlight in hip and knee joint pain areas or joint dysplasia dog- Veterinary medicine- Veterinary anatomy Concept

Diagnostic tests

Several diagnostic tests can help differentiate between tumors and cysts and determine their nature:

  • Fine needle aspiration (FNA): This procedure involves using a small thin needle to extract cells or fluid from the lump for microscopic examination. FNA provides information about the types of cells present in the growth.

  • Biopsy: A biopsy involves taking a larger tissue sample from the lump for more detailed tissue analysis. Biopsies provide a more comprehensive understanding of the growth's nature and whether it’s benign or malignant.

  • Imaging: X-rays, ultrasound, or MRI scans may be used to evaluate the internal structure of the lump and check for any spread of the growth to other parts of the body. 

Interpreting results

Once the diagnostic tests are completed, the veterinarian will interpret the results to determine the nature of the lump. If the growth is identified as a benign cyst, the vet will discuss monitoring and potential treatment options. If the lump is diagnosed as a tumor, your vet will explain whether it is benign or malignant and recommend an appropriate treatment plan. 

Treatment options

Understanding the various treatment options for tumors and cysts in dogs can help you work with your veterinarian to choose the best plan for your pet’s health and recovery.

Treatment for tumors

The treatment for tumors in dogs depends on the type, location, and whether the tumor is benign or malignant. Common treatment options include:

  • Surgical removal: This is often the preferred method for both benign and malignant tumors. Surgery involves excising the tumor along with some surrounding healthy tissue to ensure complete removal. 

  • Chemotherapy: Used primarily for malignant tumors, chemotherapy involves administering drugs to kill or slow the growth of cancerous cells. Chemotherapy can be given orally or through injections and is often used in conjunction with surgery to treat malignant cancer.

  • Radiation therapy: This treatment uses high-energy rays to target and destroy cancerous cells. It's often used for tumors that are not easily accessible by surgery or to eliminate any remaining cancer cells after surgery.

Treatment for cysts

Cysts generally require less aggressive treatment compared to tumors. Treatment options for cysts include:

  • Surgical removal: If the cyst is large, recurrent, or causing significant discomfort, surgical removal may be necessary. The procedure involves excising the cyst and ensuring that the entire sac is removed to prevent recurrence.

  • Drainage: In some cases, cysts can be drained to remove the fluid buildup. This is often a temporary solution, and the cyst may refill over time. Repeated drainage can increase the risk of infection.

  • Antibiotics: If the cyst becomes infected, antibiotics may be prescribed to treat the infection and reduce inflammation. Topical or oral antibiotics can help manage bacterial infections within the cyst.

Home care and monitoring

Old mutt terrier dog lying down on the floor near couch

Home care and monitoring play a crucial role in managing tumors and cysts. Here are some tips for pet owners:

  • Regular monitoring: Keep an eye on any lumps or masses on your dog. Note any changes in size, shape, or appearance, and report these changes to your veterinarian.

  • Follow veterinary instructions: Adhere to your veterinarian's recommendations for wound care, medication administration, and follow-up visits. 

  • Comfort and support: Make sure your dog is comfortable during recovery. Provide a quiet, anxiety-free environment, and offer plenty of love and support.

Early detection and treatment can significantly improve the prognosis for dogs with tumors or cysts. Regular veterinary check-ups and vigilant monitoring at home are key components of effective care.

Prognosis and management

Learning about prognosis and management strategies for dogs with tumors or cysts can equip you with the knowledge to enhance your pet’s care and overall quality of life.

Long-term outlook

The long-term outlook for dogs with tumors or cysts varies greatly depending on the type, size, and location of the growth, as well as whether it is benign or malignant. Benign tumors and cysts generally have a good prognosis, especially if they are effectively treated and monitored for any changes. 

Malignant tumors can be more challenging, but early detection and appropriate treatment can significantly improve the outcome. 

Regular veterinary visits

Regular veterinary visits are essential for the early detection and management of tumors and cysts. Consistent veterinary care allows for timely interventions, which can prevent benign conditions from becoming serious and ensure that any malignant conditions are treated as soon as possible.

Quality of life considerations

Maintaining your dog's quality of life is paramount, especially if they’re dealing with tumors or cysts. Here are some considerations to keep in mind:

  • Pain management: Work with your veterinarian to manage any pain or discomfort your dog may experience. This can include medications, physical therapy, or other supportive treatments.

  • Diet and exercise: Make sure your dog maintains a healthy diet and gets regular exercise to support overall well-being and strengthen their immune system.

  • Emotional support: Provide a loving, stress-free environment for your dog.

Taking these steps can help your dog live comfortably and happily, even if they’re managing a chronic condition.

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Treating your dog's tumors or cysts can get very costly. Fortunately, dog insurance is designed to help reimburse you for accidents and illnesses*, including specialized care. Just remember, covering your dog early in life can help you avoid pre-existing conditions, which generally aren't covered.

*see your policy for coverage details.

David Teich
Lead Editor

David oversees content strategy and development at ManyPets. As Lead Editor, he focuses on delivering accurate information related to pet care and insurance. David’s editorial background spans more than a decade, including a pivotal role at Digiday, where he wrote content and managed relationships with media and tech companies. As an Associate Editor at Cynopsis Media, David wrote the Cynopsis Digital newsletter and interviewed executives and digital marketing experts in the TV industry. His background also includes film journalism. His diverse experiences in journalism and marketing underpins his role in shaping content within the pet care industry.