A lipoma in dogs refers to a fatty tumor, presenting as a lump on the side, chest, or legs of the affected dog. This benign skin growth commonly occurs in older animals and is one of the most frequent subcutaneous tumors, with abdominal lipomas being rarer. The malignant form, liposarcoma in dogs, is extremely uncommon.
How does a lipoma affect the dog?
Even though a lipoma is benign, it can still cause issues. It usually manifests as soft nodules under the skin, especially in females and overweight dogs. These nodules encapsulate and form well-defined tumors that can be moved around.
However, in some cases, they may grow infiltratively, not encapsulated but invading surrounding tissue, such as muscles, displacing or merging with them. In this scenario, they are not movable and result in significant swelling in that area.
Liposarcoma in dogs is the malignant form of a lipoma and is very rare. Lipomas in dogs mostly grow on the sides of the abdomen, chest, and legs. They often become quite large and can cause problems due to their size, such as difficulties during movement. Other issues like warmth or pain are usually not present. Therefore, they do not bother the dog until they reach a certain size, often being discovered by the owner while petting the dog.
What causes a lipoma in dogs?
The causes of a lipoma in dogs are currently unknown. Suspicions point towards a hereditary predisposition, but this has not been confirmed.
What symptoms does a dog with a fatty tumor exhibit?
As there are two types of lipomas in dogs, their symptoms can vary.
- Lipoma: one or more soft, movable nodules under the skin. They are not painful and not warm.
- Infiltrative lipoma: soft and extensive. Cannot be moved and lacks a clear boundary. It may be painful. Can occur throughout the dog’s body.
Symptoms usually arise when the lipomas become very large and impair the dog’s movement. A special case is the very rare malignant liposarcoma, which typically occurs singly and is rather firm to hard. Despite this, it is poorly demarcated from the surrounding tissue.
As it tends to metastasize to the liver, bones, and lungs, it should be promptly examined if suspected. Therefore, if a dog owner notices any skin growth on their dog, it is crucial to have a veterinarian examine it. The veterinarian can determine the type and initiate timely treatment if necessary.
How is a Lipoma Diagnosed in Dogs?
The veterinarian will conduct a general examination and palpate the nodules to assess the lipomas. Lipomas can be well-recognized by an experienced examiner based on their appearance, and their nature can be determined. The veterinarian pays attention to both the texture of the nodules and their painfulness to differentiate between a “typical” lipoma and an infiltrative lipoma.
To confirm that it is indeed a lipoma and, if so, whether it is benign or a liposarcoma, further examinations are required. This involves a two-step process:
- Fine-needle aspiration biopsy: A small amount of fluid is drawn from the nodule using a syringe and examined. This harmless procedure for the dog is done to confirm that it is a fatty tumor and not another type of tumor, such as a mast cell tumor. This can be determined through a microscopic examination.
- Tissue biopsy: For further determination of the type of lipoma, a small surgical procedure is performed. The nodule is opened, and a tissue sample is taken. During this procedure, the veterinarian can directly observe whether the lipoma is infiltratively growing or not. If necessary or if there is suspicion of malignancy, it can also be removed directly.
How is a Lipoma Treated in Dogs?
A fatty tumor in dogs is usually harmless, and treatment is not mandatory. However, the condition should be regularly monitored by the veterinarian.
If the dog experiences discomfort due to the location and size of a lipoma, it can be surgically removed. A “typical” lipoma can be relatively easily removed as it is well encapsulated and does not involve other tissues.
An infiltrative lipoma requires a more extensive surgical removal, involving the removal of adjacent tissue. If it is fused with tendons, the procedure becomes more complex.
In the case of a rare liposarcoma, a large amount of healthy tissue around it must be removed. This is done to ensure the complete removal of all malignant cells. Subsequently, radiation and/or chemotherapy may be administered. Both are not necessary for benign lipomas.
What Should the Owner of an Affected Dog Consider? Can it be Prevented?
Lipomas can recur, so the dog should be regularly examined, and new nodules should be promptly shown to the veterinarian. This allows for quick action if necessary.
Simple lipomas rarely recur and do not proliferate as much as infiltrative lipomas. The prognosis is also somewhat worse for infiltrative lipomas even after removal. They tend to reoccur more frequently and can cause long-term damage to tissues such as muscles and tendons.
The prognosis for liposarcoma is not as favorable as for benign forms. It depends heavily on the size and location, as well as the success of the operation and follow-up treatment. During surgery, it is crucial to determine whether all tumor tissue could be completely removed, which may not always be possible due to surrounding structures. The amount of tissue that can be removed is limited, especially around the leg. Additionally, the prognosis depends on whether the tumor has already metastasized, and if there are existing metastases.
Prevention is not possible as the direct cause of lipoma formation in dogs is not yet known.
