Tumors of the Adipose (Fat) Tissue in Cats and Dogs
Lipomas (benign tumors)
Lipomas refer to benign (noncancerous) tumors of the fat tissue that can be distinguished from the malignant liposarcoma
tumors by
cytology or biopsy. They are relatively common in older dogs, especially in subcutaneous locations (the layer of
tissue directly underlying the skin), however, they can also occur in the chest cavity, abdominal cavity, spinal canal, and
the vulva nad vagina of dogs. They rarely cause any symptoms but can become a medical problem once they reach a size
large enough that can compress onto and interfere with adjacent tissues/organs. Once the lipomas begin to cause medical
problems in the pets, they are usually surgically removed which can be followed by radiation therapy to ensure that the
tumor won't grow back.

Intermuscular lipomas are a variant of the subcutaneous lipoma and are located in the intermuscular region of the thigh of
dogs. They can occasionally cause lameness and are recommended to be surgically removed.

Infiltrative lipomas (infiltrative tumors)
This is a relatively uncommon tumor that is differentiated from simple lipoma or liposarcoma by cytology or biopsy. They
are considered benign (noncancerous) and do not
metastasize (spread) to distant organs, however, they can invade
immediately adjacent tissues such as muscle, joint capsule or even bone. CT (computed tomography) imaging is used to
better characterize the mass but it can be difficult to distinguish the benign fat tumor from normal fat. Depending on the
location and extent of the tumor, surgical removal with or without radiation therapy has been used in some cases.

Liposarcomas (malignant tumors)   
Liposarcoma, a type of soft tissue sarcoma cancers, is an uncommon malignant tumor that originates from fat cells in older
dogs. It is usually reported in subcutaneous locations, especially along the extremities, but can occur in other sites such as
the abdominal cavity or bone. Liposarcomas can be distinguished from lipomas by
cytological examination of the cells
under the microscope. These tumors are locally invasive and, unlike lipomas, also have a low potential to spread
(metastasize) to distant organs in the body such as the lungs, liver, spleen, and bone. The prognosis for pets diagnosed
with liposarcoma is good as long as appropriate complete surgical removal has been done.

Are there any clinical trials investigating new treatments?
There are several clinical trials ongoing for dogs with soft tissue sarcomas in pets, which are partially funded by the
institutions. To learn more about these trials, please visit the
Clinical Trials for Soft Tissue Sarcoma in Dogs section.

Additionally, there are several clinical trials available for cats and dogs with any tumor type for which your pet may qualify.
To learn more these trials (which are partially or fully funded by the institutions), please visit the
Dog Clinical Trials (any
tumor type) or Cat Clinical Trials (any tumor type) section.  

To learn more about veterinary clinical trials in general, please visit the
Pet Clinical Trials section.

Do cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role in
educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets is to
prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.

To learn more about how to recognize pain in pets with cancer and what cancer pain management options are available for
your pet, please visit the
Cancer Pain Management section.

How important is nutritional support for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for example,
some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).

Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need to
be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more, please
visit the
Cancer Nutrition section.

Finding a qualified veterinary oncologist
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "
Locate a veterinary oncologist" section.  

Additional online resources

  • Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
  • Morrison Wallace B. Cancer in Dogs and Cats: Medical and Surgical Management. Baltimore: Williams&Wilkins, 1998
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017
Comprehensive guide to cancer diagnosis and treatment in cats and dogs