What causes this type of tumor?
The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary.
How are these types of tumors diagnosed?
Typically, these types of tumors can be diagnosed by fine needle aspiration (FNA). FNA involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide.
In some cases, results from FNA may not be entirely clear and a biopsy may be necessary. A biopsy is the surgical removal of a piece of the tumor. Pieces of the tumor are then examined by a veterinary pathologist under the microscope (histopathology). Histopathology is helpful to make a definitive diagnosis. Advanced imaging, such as a CT scan, may also be recommended.
What is a fatty tumor (lipoma)?
Lipomas, also known as adipose tissue tumors, arise from fat deposits that grow at a different rate from the surrounding fat, leading to the formation of a lump below the skin of dogs (humans get them, too). The pronounced lump often feels soft and moveable, and is usually not attached to the muscle below. The tumor is usually well-encapsulated, meaning it has a defined border, which makes it easy to remove surgically, if needed.
Lipomas are usually harmless, but in certain locations — such as under the armpit or in the groin — they can limit mobility. The majority are benign, meaning they’re not cancerous and will not spread (or metastasize) throughout the body in the way malignant tumors can. However, some dogs will form multiple lipomas in various locations on their body throughout their life.
There is also a more aggressive form of lipoma, called an infiltrative lipoma. This type of growth is still benign but has less defined borders and is more difficult to remove surgically.
Note: “Lipoma” sounds very similar to, but is not the same as, lymphoma in dogs, which refers to a very aggressive form of cancer in the lymph nodes.
In very rare cases, a fatty tumor is actually a malignant growth called a liposarcoma. This type of cancerous mass develops from fat cells, grows quickly, is very locally invasive, but will rarely metastasize (or spread) to other areas of the body.
Liposarcomas require aggressive surgery to remove. Unfortunately, depending on the tumor’s size, location, and invasiveness, it may not be possible to remove it entirely. For these cases, follow-up therapy, such as radiation, is recommended.
Masses on a dog. When to worry and when to remove. Lipoma on an older lab.
If you notice a lump has appeared overnight on your dog’s neck, chest, leg, or back, don’t panic. Many pet parents will fear their dog has cancer, but before you jump to the worst-case scenario, schedule an appointment with your vet to evaluate the lump. It may be a lipoma.
A lipoma is a common type of tumor that affects approximately 16% of dogs1. Though the word “tumor” may sound frightening, it’s important to know that these abnormal growths are benign fat build-ups and typically harmless.
In this article, we’ll cover everything you need to know about canine lipomas, removal costs, treatment methods, and more.
Pro Tip: Not sure whether you should take your dog to the vet to get a lump checked out? With pet insurance, you can worry less about the cost of vet visits with peace of mind knowing that you’ll be reimbursed for out-of-pocket expenses spent on covered medical conditions.