Benign Tumors in Dogs and Cats: Symptoms, Diagnosis, and Treatment
A lump found on or under the skin of a dog or cat does not necessarily mean cancer. Benign tumors, also known as non-cancerous tumors, are among the common masses seen in pets. They generally grow slowly, do not spread to distant organs, and have a low risk of recurrence when completely removed. However, it is not possible to determine whether a mass is benign simply by looking at its appearance or feeling its texture. A veterinary examination and, when necessary, cytological or histopathological evaluation are important for an accurate diagnosis. In this article, we explain what benign tumors are, their symptoms, how they are diagnosed, when treatment may be necessary, and what pet owners should know about monitoring these masses.
What Is a Benign Tumor?
Benign tumors develop when cells multiply in an uncontrolled but limited manner, resulting in masses that are generally well-defined and sometimes encapsulated. They usually remain localized, do not invade surrounding tissues, and do not spread to distant organs through metastasis.
These tumors typically grow slowly and may have clearly defined borders. Some benign tumors are encapsulated, and when they are completely removed surgically, the risk of recurrence is generally low.
Common benign tumors found in dogs and cats include:
Lipomas
Fibromas
Papillomas (wart-like growths)
Histiocytomas
Certain benign skin-origin masses
An important point to remember is that not every slow-growing or movable mass is benign. Some malignant tumors may initially have similar characteristics. For this reason, newly discovered or growing masses should be evaluated by a veterinarian.
What Is the Difference Between Benign and Malignant Tumors?
Tumors are generally classified as benign or malignant.
Benign tumors usually remain localized to the area where they develop, while malignant tumors may invade surrounding tissues and, in some cases, spread to other parts of the body through the blood or lymphatic system.
However, benign and malignant tumors cannot be reliably distinguished by appearance alone.
Depending on the case, a veterinarian may recommend:
Fine-needle aspiration (FNA)
Cytological examination
Biopsy
Histopathological examination
Diagnostic imaging
These methods help determine the nature of the mass and establish an accurate diagnosis.
Symptoms of Benign Tumors in Dogs and Cats
The signs of a benign tumor can vary depending on its location and size.
Common characteristics may include:
A mass noticed on or under the skin
A generally well-defined and movable mass
Slow growth
Usually little or no pain
No obvious redness or signs of inflammation
Cosmetic concerns in some cases
Functional problems when the mass is located near the eyes, mouth, or joints
For example, a mass around the eye may interfere with vision, while a mass in the mouth may cause problems with chewing or eating. Masses located near joints can sometimes restrict movement.
How Are Benign Tumors Diagnosed?
When a mass is detected, the veterinarian will first perform a thorough physical examination.
1. Physical Examination
During the examination, the veterinarian evaluates the mass's:
Size
Shape
Consistency
Mobility
Depth
Relationship with surrounding tissues
The veterinarian may also assess whether the mass has changed over time and whether it affects the animal's daily activities or quality of life.
2. Fine-Needle Aspiration (FNA)
Fine-needle aspiration (FNA) is a minimally invasive technique used to collect cells from a mass for examination.
The collected sample can be evaluated cytologically and may provide valuable information about the nature of the mass. However, FNA does not always provide a definitive diagnosis in every case.
3. Histopathological Examination
When FNA results are inconclusive or the mass is considered suspicious, a biopsy or complete surgical removal followed by histopathological examination may be necessary.
Histopathology allows the tumor cells and tissue structure to be examined under a microscope and can help determine the tumor type and its biological behavior.
4. Diagnostic Imaging
Ultrasound and other imaging techniques may be recommended for large, deep-seated masses or tumors located close to important anatomical structures.
Imaging can help evaluate the relationship between the mass and surrounding tissues and may also assist with surgical planning when necessary.
Do Benign Tumors Require Treatment?
Not every benign tumor needs to be surgically removed.
The treatment approach depends on the tumor's size, location, growth rate, and effect on the pet's quality of life.
Monitoring and Observation
Some small, stable masses that do not cause discomfort or functional problems may simply be monitored.
The veterinarian may periodically measure the mass and evaluate its characteristics to monitor its growth behavior over time.
Surgical Excision
Surgical removal may be recommended for benign masses that are growing, causing discomfort, interfering with normal functions, or creating significant cosmetic concerns.
Surgical excision may also allow the removed tissue to be submitted for histopathological examination, helping establish a definitive diagnosis.
Cryotherapy and Laser Excision
For certain superficial benign growths, techniques such as cryotherapy or laser excision may be considered as alternative treatment options. The most appropriate method depends on the type, size, and location of the mass.
What Is the Prognosis for Benign Tumors?
The prognosis for most benign tumors is generally excellent.
When a benign tumor is completely removed, the likelihood of recurrence is usually low, and these tumors typically do not have a negative effect on life expectancy.
However, not all masses behave in the same way. Therefore, newly detected masses or masses that change over time should be properly evaluated by a veterinarian.
What Should Pet Owners Watch For?
When you notice a new mass on your dog or cat, the safest approach is to consult your veterinarian rather than assuming that it is benign.
When monitoring a mass at home:
Check its size regularly.
Observe any changes in its shape or consistency.
Monitor for rapid growth.
Look for redness, bleeding, or ulceration.
Observe whether the mass causes pain or discomfort.
Pay particular attention to masses around the eyes, mouth, or joints.
Follow your veterinarian's recommended monitoring schedule.
When Should a Mass Be Examined by a Veterinarian?
Every newly discovered mass in a dog or cat should be evaluated by a veterinarian. Veterinary assessment should not be delayed, particularly when:
The mass is growing rapidly
Its shape or consistency changes
Bleeding or ulceration develops
The mass becomes painful or sensitive
It affects movement
It causes difficulty eating or chewing
It is located around the eye and affects vision
A previously evaluated mass starts growing again
Frequently Asked Questions
Are benign tumors cancer?
No. Benign tumors are non-cancerous tumors that generally do not invade surrounding tissues or spread to distant organs. However, a mass cannot be reliably classified as benign based on appearance alone.
What is one of the most common benign tumors in dogs?
Lipomas are among the most common benign tumors of fatty tissue found in dogs. However, not every lump under a dog's skin is a lipoma and should be assumed to be one without veterinary evaluation.
Can cats develop benign tumors?
Yes. Cats can also develop various benign tumors and non-cancerous masses. Veterinary evaluation may be necessary to determine the type and nature of a mass.
Does a benign tumor need to be removed surgically?
Not necessarily. Small and stable masses may be monitored. However, surgical removal may be recommended when a mass is growing, causing discomfort, or interfering with normal body functions.
Can a benign tumor come back?
Many benign tumors have a low risk of recurrence when completely removed. However, the risk can vary depending on the specific tumor type and whether complete surgical removal was achieved.
Conclusion
Many masses found in dogs and cats may be benign, but a mass that looks harmless should not automatically be assumed to be benign. Early evaluation, accurate diagnosis, and appropriate monitoring are important for identifying potential risks.
If you notice a new mass on your pet or observe changes in the size, shape, or appearance of an existing mass, we recommend having it evaluated by a veterinarian.
Veterinary Clinical Oncology
At Veterinary Clinical Oncology, we provide a scientific and patient-focused approach to the diagnosis, treatment, and monitoring of tumors and cancer in dogs and cats, with a focus on veterinary oncology.
Disclaimer
This article is intended for general informational purposes only and does not replace an individual veterinary examination, diagnosis, or treatment recommendation. If you notice any mass on your pet, we recommend consulting a veterinarian as soon as possible.
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