Lipoma (Fatty Tumor) in Dogs

Overview of Lipoma (Fatty Tumor) in Dogs

A lipoma is a benign fatty tumor usually composed of mature fat cells. They are usually soft, well defined, and subcutaneous (under the skin). Lipomas are variable in size and shape and may occur anywhere, although they are commonly found on the ventral (under) surfaces of the chest and abdomen.

All dog breeds may be affected, but they are most common in older dogs, especially older female dogs. Lipomas are very common in dogs, and less common in cats.

Infiltrative lipomas are those that develop in deeper tissue and between muscle layers. These lipomas tend to be firmer and more broad-based than typical lipomas. These tumors also grow slowly, but are more invasive and less well defined. They grow by expanding into the tissue and may cause pain. Infiltrative lipomas are much less common than typical lipomas.

What to Watch For

Signs of fatty tumors in dogs may include:

• Skin swellings
• Lumps and bumps
• Usually they are spherical or oval in shape

Diagnosis of Lipomas in Dogs

Your veterinarian may recommend the following diagnostic tests:

• Fine needle aspirate. This easy diagnostic test involves placing a needle attached to a syringe into the mass and withdrawing a sample of cells. The contents of the needle and syringe are expelled onto a glass slide for analysis.
• Cytology. The slides are evaluated microscopically for evidence of adipose (fat) cells.
• Biopsy. If there is no conclusive evidence on aspiration, a biopsy (tissue sample) may be taken. If the mass is small, an excisional biopsy, which is a biopsy where the entire mass is removed, may be done. Biopsies usually require sedation with local anesthesia or general anesthesia.

Treatment of Lipomas in Dogs

If a lipoma is small and slow growing, your veterinarian may advise an owner to observe the mass for any changes. If there are no significant changes, treatment is not necessary. In other cases, the following treatments are available:

• Excision (removal) of a lipoma should be considered if it is growing rapidly, causing discomfort, or it interfering with the mobility or life style of the animal.
• Infiltrative lipomas should be aggressively treated with a wide surgical excision. Most of the times, excision will be incomplete, as some of the tumor cells will remain on the body. If the remaining tumor is slow to return, this may be all the treatment needed.
• Radiation therapy is available if the lipoma is invasive and cannot be completely removed.
• If surgery is required to remove a lipoma, preoperative blood work (complete blood count and profile) are generally recommended.

Home Care

Note any changes in previously diagnosed lipomas that are not being treated. Significant changes should be re-evaluated.

After a lipoma has been removed, watch the incision for any swelling, redness or discharge. Make sure your pet is not licking or chewing at the incision line. Sutures are generally removed in 7 to 10 days.

There is no way to prevent the occurrence of lipomas. Once lipomas are noted, they should be closely monitored. Lipomas should not be allowed to become so large that they are difficult to remove or they interfere with function.

Infiltrative lipomas may need more aggressive treatment.