How Do I Know If My Dog Has An Infiltrative Lipoma?

What are infiltrative lipomas in dogs?

Infiltrative lipomas are benign fatty tumors that grow invasively into surrounding tissues in dogs, as opposed to regular lipomas which are encapsulated and noninvasive (Livs). Infiltrative lipomas often originate in the subcutis and spread between tissue planes into underlying muscles, nerves, and fascia (Ethosvet). These tumors commonly develop on the torso, legs, head and neck of dogs (NCBI).

Common Symptoms

Some of the most common symptoms of infiltrative lipomas in dogs include:

  • Lumps under the skin – Infiltrative lipomas often start out feeling like benign fatty tumors under the skin. However, they tend to grow larger and feel firmer than regular lipomas. The lumps are not discrete but rather feel interconnected under the skin (1).
  • Pain or discomfort – As infiltrative lipomas invade surrounding tissues, they can cause pain and discomfort. They may limit mobility if growing around joints or impinge on nerves. Dogs may cry out or whine when pressure is applied to affected areas (2).
  • Difficulty moving – Lipomas that infiltrate muscle tissue can make movement difficult and awkward. Dogs may hesitate to run, jump, or climb stairs. They may also develop limping or lameness in affected limbs (3).
  • Changes in appetite – If lipomas press on internal organs or impede breathing, dogs may show reduced appetite. Weight loss may also occur even if eating normal amounts. Pain may also suppress appetite (4).

In some cases, infiltrative lipomas may not initially cause any symptoms noticeable to owners. But they will still slowly invade surrounding tissues. Catching them early allows for more treatment options.


Diagnostic tests

If an infiltrative lipoma is suspected, the veterinarian will perform a thorough physical exam, feeling for any abnormalities in the skin, fat, or muscle tissue (Ethosvet, 2016). This may help narrow down the location for further testing.

The next step is often a fine needle aspirate of cells from the mass. This involves inserting a small needle into the tumor and pulling out cells for examination under a microscope. If the aspirate shows fat cells, it supports a lipoma diagnosis, but cannot definitively differentiate between a regular lipoma and an infiltrative lipoma (NCBI, 2013).

For a definitive diagnosis, a surgical biopsy is required. This involves surgically removing all or part of the mass and sending it for pathological analysis. Examining the tissue under a microscope can reveal if the fatty tumor has infiltrated the muscles, fascia, nerves, or other structures (Animalsurgicalcenter, n.d.).

Advanced imaging such as x-rays, CT scans, or MRIs may also be used. These imaging tests can reveal the tumor’s size, location, and any spread into surrounding tissues (Ethosvet, 2016). However, a biopsy is still needed to confirm it is an infiltrative lipoma.

Treatment options

There are a few main treatment options for infiltrative lipomas in dogs:1

Surgery is often the first line of treatment. The goal is to remove as much of the tumor as possible. However, infiltrative lipomas can be difficult to fully excise due to their invasive growth. Aggressive surgical removal may help slow the progression of the disease.

Pain medication may be prescribed to keep the dog comfortable before and after surgery. Common medications include NSAIDs, tramadol, gabapentin, or steroids.

Radiation therapy may be used alone or in combination with surgery to improve local tumor control. It helps destroy remaining cancer cells and reduce pain. Treatments are typically scheduled a few times per week for 4-6 weeks.

Recovery and aftercare

The recovery period after infiltrative lipoma surgery in dogs varies but generally takes several weeks to months. Incision care is crucial during recovery to prevent infection and allow proper healing. The vet will likely prescribe antibiotics, anti-inflammatories, and pain medication. The incision site should be monitored daily for signs of infection like discharge, swelling or redness. Some mild swelling and bruising around the incision is normal initially. Keep the area clean and dry. An Elizabethan collar may be recommended to prevent licking or chewing at the stitches. Stitches are often absorbable and do not need to be removed.

Activity will need to be restricted during recovery to allow the surgical site to heal. The vet will provide instructions on limiting activity, which often means no running, jumping or rough play. Short, leashed walks are recommended to allow the dog to relieve itself. Over-activity can cause internal bleeding, swelling or seromas to develop. Close confinement or crate rest may be prescribed for the first few weeks. Increased activity can gradually be resumed over several weeks as long as the incision site is healing properly.

Follow-up vet visits are crucial to monitor recovery and check for recurrence. The vet will want to examine the surgery site and may recommend periodic bloodwork or imaging tests to look for signs of remaining cancer cells. Recurrence rates are high with infiltrative lipomas despite surgery. Early detection improves the chances of successful retreatment if the cancer returns. Most dogs will need lifelong periodic vet checks after infiltrative lipoma surgery. Additional surgery, radiation or chemotherapy may be warranted if the cancer recurs. With an aggressive combination treatment approach, survival times up to 4 years have been reported in some dogs after infiltrative lipoma surgery.


With early detection and treatment, dogs with infiltrative lipomas generally have a good prognosis. However, infiltrative lipomas can be challenging to fully remove or control. Studies show around a 40% recurrence rate within the first 8 months after surgery.

Regular monitoring and check-ups are crucial even after treatment. If the lipoma does recur, additional surgery, radiation, chemotherapy, or alternative therapies may be pursued. With a combination approach, median survival times of 6 months to 4 years have been reported. Prompt veterinary care and owner vigilance are key to maximizing prognosis.


Unfortunately, there is no known way to prevent infiltrative lipomas from developing in dogs [1]. However, there are some steps dog owners can take to try to minimize their dog’s risk:

Monitor your dog’s body frequently for any new lumps or bumps. Catching an infiltrative lipoma early can allow for more treatment options. Perform monthly checks of your dog’s body to look for any changes.

Maintain a healthy weight for your dog. Obesity is a risk factor for many cancers in dogs, and likely also increases the risk of infiltrative lipomas. Feed your dog an appropriate diet for their size, breed, and activity level, and avoid overfeeding.

Bring your dog for annual wellness checkups at the veterinarian. Your vet can monitor for any suspicious lumps during the physical exam. Staying current on exams and vaccines supports your dog’s overall health.


Infiltrative lipoma treatment in dogs can become quite expensive depending on the type and extent of care needed. Some costs to expect include:

The initial veterinary exam to diagnose an infiltrative lipoma usually costs $50 to $100. Your vet may recommend additional diagnostic tests like an aspirate, biopsy, or imaging which can range from $100 – $500 (Source).

If surgery is recommended, infiltrative lipoma removal can cost $500 – $3,000+. This is considered a complex procedure that requires general anesthesia and expert surgical skills. The large size and infiltrative nature makes full removal challenging (Source).

Medications, follow-up exams, physical therapy, and other treatments will incur additional expenses. Pet insurance can help manage the costs by reimbursing vet bills.

Overall, owners should budget several hundred to a few thousand dollars to treat an infiltrative lipoma. Getting an accurate diagnosis first allows you to better estimate the total costs involved.

When to seek help

You should take your dog to the vet if you notice any new lumps or bumps. While lipomas are generally benign, any new growth could potentially be cancerous. It’s important to have your vet examine and test any new lumps or bumps to determine if they are harmless lipomas or something more serious.

Look out for changes in your dog’s behavior as well. If your dog is normally active but becomes reluctant to run or play, take them to the vet. Difficulty moving or signs of pain when the lump is touched warrant an urgent vet visit.

According to Embrace Pet Insurance, you should have your vet evaluate fast-growing lumps over a 2-4 week period. Rapid enlargement may indicate a more serious issue. Schedule an appointment if the lump interferes with your dog’s mobility or quality of life.

While most lipomas are benign, it’s better to be safe than sorry. Seek veterinary care for any suspicious new lumps or bumps. Early evaluation and treatment can lead to better outcomes if cancer is detected.


Infiltrative lipomas are fatty tumors that can develop in dogs under the skin, in the subcutaneous tissue, and sometimes invade the muscle. While lipomas are typically benign, infiltrative lipomas can cause problems due to their size and location.

Getting an accurate diagnosis involves a veterinary exam, palpation of the lump, imaging tests like x-rays or ultrasound, and sometimes a biopsy. Treatment usually involves surgery to remove the tumor. The prognosis is generally good if infiltrative lipomas are diagnosed and treated promptly before they spread or cause issues.

With surgical removal and proper aftercare, most dogs recover well. However, infiltrative lipomas can recur in some cases. Catching them early and monitoring lumps regularly are key to minimizing complications. Overall, being aware of the signs and seeking veterinary assessment can help dog owners address infiltrative lipomas effectively.

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