A ‘lump’ is typically a general term to describe a swelling on or under the skin. Lumps can either be a primary issue or secondary to systemic or environmental changes. Understanding the potential causes, diagnostic steps, and treatment options can help you determine when to seek veterinary care.
Possible Causes of Lumps in Pets
Lumps in pets can result from a number of factors, ranging from local to systemic causes, and from internal (individual) to external (environment) causes. Some common causes include the following:
1. Food Allergies or Sensitivities
Some pets may develop adverse skin reactions to certain ingredients in their diet, leading to inflammation, swelling, and excessive licking in certain areas (between digits and paw pads). Secondary infections (abscess, cyst) may form as a result. In such cases, switching to a hypoallergenic or limited-ingredient diet under veterinary guidance can help manage symptoms effectively. Ant bites, bee stings, and vaccines may lead to an allergic reaction, thus hives may develop in a region or throughout the skin.
2. Infections
Bacterial, viral, fungal, or parasitic infections (such as papilloma virus in dogs, feline immunodeficiency and leukemia viruses in cats, Coccidioidomycosis, fleas, ticks, and mites) can lead to the development of lumps. These infections often have the potential to cause additional symptoms such as decreased appetite, fever, lethargy, weight loss, and dehydration. Prompt veterinary attention is essential to diagnose and treat the underlying infection, which may require antibiotics, anti-parasitic medications, antifungal medications, or supportive care including fluids, gastrointestinal support, and pain medications. Some infections may warrant aggressive treatment where hospitalization is necessary to aid in recovery.
3. UV/Sun Exposure
Solar-induced lumps may develop secondary to excessive sun exposure (sunbathing dogs, outdoor cats). Thin/short hair and less skin pigmentation may predispose certain breeds to solar-induced lumps. Sunscreen may be considered, but caution must be used with products that warn about toxicity from ingestion. Pet-safe sunscreen options are available.
4. Immune-mediated Disease
The body’s immune system may target normal tissues leading to swelling, inflammation, and development of lumps. Certain immune-mediated diseases may target cells/proteins that help support the skin’s normal integrity (Panniculitis, Pemphigus).
5. Cancer
Tumors involving the skin may develop as the primary cause (Fibrosarcoma/Soft tissue sarcoma) or secondary seeding of cancer cells from other areas of the body (Osteosarcoma, Hemangiosarcoma).
Identifying and Staging the Lump
If your pet develops a lump, your veterinarian may recommend a series of diagnostic tests to identify and evaluate the extent of disease. These tests include:
- Physical Examination: Checking for other lumps on the body, and lymph node and organ enlargement
- Blood Tests: Evaluating organ function, infection, or metabolic disorders that may be related to the lump.
- Fine Needle Aspiration and Cytology: Non-invasive collection of cells with a needle to identify the type of mass.
- X-rays, Ultrasound, Computed Tomography (CT): Screening for spread of the lump to other organs (lungs, liver, spleen, internal lymph nodes).
- Biopsy and Histopathology: Removal of part or all of a lump to identify, categorize, and evaluate cell behavior.
- Genetic sequencing: Additional testing to evaluate genetic markers of cancer cells to help identify weaknesses that may be targeted with specific treatment(s)
When to Seek Veterinary Care
While a small lump may not seem urgent, we still recommend contacting your veterinarian if one or more of the following criteria are met:
- Larger than the size of a pea
- Present for 30 days or longer
- Growing and changing appearance
- Causes chewing, biting, licking, and/or scratching
- Associated with redness, pain, bleeding, swelling, and/or discharge
Treatment Options for Lumps
Treatment depends on the underlying cause and may include:
- Dietary Management: Prescription diets designed for food allergies
- Medications: Treating underlying diseases, infections and managing dietary allergies.
- Surgery: Removing lumps for identification and evaluation
- Radiation: High-dose and Low-dose treatments of radiation to destroy cancer cells. A local/regional treatment option to address tumors that were incompletely removed, tumors that are not surgical, and palliative treatment for addressing pain and swelling
- Electrochemotherapy: Uses a combination of low-dose chemotherapy and electrocautery to increase chemotherapy levels within cancer cells and to cauterize blood flow to tumor cells. Most commonly used as a local/regional treatment option to address tumors that were incompletely removed. Less commonly used as a standalone treatment option for tumors in the US.
- Chemotherapy: A systemic treatment option involving intravenous and/or oral administration. General chemotherapy and targeted chemotherapy options are available. Can be used as a palliative option for pain and swelling
Addressing Lumps in Pets
While not all causes of lumps are preventable, you can take steps to minimize the risk:
- Feed a balanced, high-quality diet that your pet enjoys.
- Keep up with routine veterinary check-ups, blood testing, imaging, and vaccinations once to twice yearly.
- Document changes with video or pictures after a lump is identified.
- Early identification and removal can limit disease progression
- Administer medications as prescribed to limit resistance and recurrence
Conclusion and Next Steps
Lumps can develop for many different reasons. Early detection and treatments may help limit the extent and progression of disease. If there is ever concern about a lump, please seek guidance from your veterinarian.
