고양이 지방종 vs 악성 지방육종 증상과 원인, 진단·치료와 관리 포인트 총정리

Is the Lump Under Your Cat’s Skin Benign or Malignant? — Key Points for Distinguishing Lipomas from Liposarcomas

Oncology/CancerDiseasesMeongsiljang Veterinary Advisory Board

Feline lipomas are common benign tumors, whereas liposarcomas are malignant, invasive tumors with a high risk of metastasis. Accurate diagnosis is key.

What Are Feline Lipomas and Malignant Liposarcomas?

Image of a lipoma that has developed under a cat's skin

Feline lipomas are benign tumors caused by the abnormal proliferation of fat cells. They typically develop under the skin and are characterized by slow growth, a soft texture, and mobility. However, while lipomas are common in dogs, they are relatively rare in cats. In contrast, liposarcomas are malignant tumors arising from fat cells that can invade local tissues and have the potential to metastasize. - Lipoma: Benign; surgical removal is an option if the tumor grows large or interferes with movement. - Liposarcoma: The prognosis is significantly influenced by complete surgical excision whenever possible. Because these two tumors can appear similar externally, a biopsy is necessary to distinguish their nature and determine the appropriate treatment approach.

What Are the Main Causes of Lipomas and Malignant Liposarcomas?

The exact cause of lipomas remains unclear. However, they are most commonly seen in older animals, and obesity is known to be a contributing factor. Similarly, there is no single, clearly identified cause for malignant liposarcomas, and information regarding their development is limited. To date, there is no strong evidence suggesting that specific breeds are more prone to developing these tumors. - Senior Cats: Lipomas are more frequently observed in older animals. - Weight Management: Since obesity can be a contributing factor, maintaining a healthy weight is beneficial. Regular checks of the skin and underlying tissues are important for early detection.

Comparison image of normal and abnormal proliferation of fat cells

Check for Key Symptoms and Signs

Feline lipomas typically grow slowly and present as soft, movable lumps. In contrast, malignant liposarcomas tend to enlarge rapidly, feel firm, and are often fixed to the skin. While both tumor types may be painless, malignant ones can invade surrounding tissues. Please watch closely for the following signs.

Subcutaneous lump: Be cautious if a soft, movable lump on the body continues to grow for more than two months.

Firm lump: The development of a hard, fixed lump suggests a higher likelihood of malignancy.

Skin changes: Redness or peeling of the skin around the lump may indicate inflammation or tissue invasion.

Mobility issues: If a lump forms near a joint, it can restrict movement.

Weight loss: Malignant tumors may be accompanied by systemic symptoms, including weight loss.

Images of subcutaneous lumps and skin changes in cats

Situations Requiring Immediate Veterinary Attention

If a lump grows rapidly within a month, feels fixed and immovable, or is accompanied by redness or peeling of the skin, immediate veterinary attention is necessary. Signs of pain, decreased appetite, and reduced activity levels may indicate a malignant condition.

Diagnostic Methods for Accurate Diagnosis

An accurate diagnosis begins with a physical examination by a veterinarian. This is followed by an ultrasound to assess the mass's boundaries, density, and blood flow. - Tissue Examination (FNA or Biopsy): Cytological analysis is used to clearly determine whether the mass is benign or malignant. For malignant liposarcoma, chest X-rays or abdominal ultrasounds are also performed to check for metastasis. - Imaging Tests: These are essential for determining whether the cancer has spread. Starting treatment without a proper diagnosis can lead to incorrect management, so thorough and accurate testing is absolutely necessary.

Image of a fine-needle aspiration test for a subcutaneous mass in a cat

Treatment Options and Step-by-Step Approach

If a lipoma is small and asymptomatic, observation alone is sufficient. However, if the mass grows or interferes with movement, surgical removal is recommended. For malignant liposarcoma, complete removal is the top priority. In some cases, additional radiation therapy or chemotherapy may be necessary after surgery. - Surgical scope: It is important to remove the tumor along with surrounding normal tissue. - Prevention of recurrence: Regular imaging tests are essential for monitoring after surgery. The treatment plan varies depending on the tumor's size, location, and whether it has metastasized.

Surgical images of a cat with malignant liposarcoma

Home Care and Precautions

After surgery, keep the wound area clean and use an Elizabethan collar or cage to prevent your cat from scratching it. For malignant liposarcoma, regular vet visits and imaging tests are essential to carefully monitor for recurrence. Feed a balanced diet and prevent obesity. Creating a low-stress environment also helps. - Regular check-ups: For senior cats, we recommend check-ups every 3 to 6 months. - Environmental management: Maintain a comfortable space for your cat.

An image of a cat in a calm, stable environment after surgery

Preventing Recurrence and Breed-Specific Considerations

Invasive tumors, including malignant liposarcomas, have a high rate of local recurrence if incompletely excised, making regular postoperative check-ups and imaging monitoring essential. To date, no clear evidence has been reported that specific breeds are more susceptible to this tumor; therefore, regardless of breed, it is important to closely monitor older cats for any changes in the size, firmness, or fixation of lumps.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Are lipomas malignant?

Lipomas are benign tumors. However, it is difficult to definitively distinguish between benign and malignant tumors based solely on appearance or palpation, so confirmation through a fine-needle aspiration (FNA) biopsy is the most accurate approach.

Is malignant liposarcoma treatable?

If the tumor is completely removed through wide surgical excision, the prognosis is generally favorable. However, if the excision is incomplete, local recurrence is common, and additional radiation or chemotherapy may be necessary for progressive or recurrent cases.

Do lipomas grow?

Lipomas typically grow slowly. However, if they become large enough to interfere with movement, surgical removal should be considered.

How can you tell the difference between a lipoma and a malignant liposarcoma?

We differentiate the condition by analyzing the morphology and characteristics of cells through fine-needle aspiration (FNA), and if necessary, we confirm the diagnosis with a biopsy (histopathology). Since cytology and histopathology results can differ, tissue biopsy is often preferred.

Can cats develop lipomas?

Yes, cats can develop both benign lipomas and malignant liposarcomas. However, lipomas are common in dogs but relatively rare in cats.

Comparison Table: Lipoma vs. Malignant Liposarcoma

Item	Lipoma	Malignant Liposarcoma
Nature	Benign	Malignant
Growth rate	Very slow	Fast
Mobility	Movable	Fixed
Metastatic potential	None	High
Treatment method	Observation or surgery	Surgery + radiation/chemotherapy

An accurate diagnosis is possible only through a tissue biopsy. Since symptoms can be identical, consultation with a veterinarian is essential.

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References

[1] Veterinary Surgical Oncology, 2nd Edition. 2018. Wiley-Blackwell.

[2] Clinical Medicine of the Dog and Cat, 4th Ed. 2015. Elsevier.

[3] BSAVA Manual of Canine and Feline Dermatology, 4th Ed. 2019. BSAVA Publications.