Background:
 Composed of mature fat cells and connective tissues, a lipoma is a benign growth commonly felt beneath the skin in dogs. These "fatty tumors" are quite common in middle-aged and older female dogs, although they affect both sexes. Generally, they do not pose a serious health risk to pets, although occasionally they can grow quite large and begin to cause problems.

A tumor is a lump of cells that does not obey the normal rules of cell growth. Normally, cells grow until chemical messengers in the body tell them to stop growing. Tumor cells do not listen to these messengers and continue to grow. There are two types of tumor. The first type is called benign, usually growing slowly and does not generally spread to other parts of the body. The other type of tumor is malignant, which push through nearby organs or may spread to other tissues. Most fatty tumors are benign. They are neither painful, nor will they cause serious problems unless they grow between muscles or are so large that they cause mechanical problems, such as difficulty walking. Though rare, fatty tumors may become malignant, in which case they need to be surgically removed. Hopefully, your pet's tumor does not match any of the above criteria. It is very important that you keep a close watch on your pet's tumor. Although your pet's tumor is not a problem at this point in time, it may become a problem later down the road. It is good to document the size of your pet's tumor using general terms to identify the size (pea size, egg size). Each month you should reevaluate the size of the tumor. If any changes occur, you should contact your veterinarian immediately. Your veterinarian can evaluate the size and appearance of your pet's growth at each subsequent examination and stay alert, well in advance, if surgery becomes necessary. With a little extra care, you make sure that your pet lives a long, happy, healthy life.

Clinical Signs:
Lipomas appear as bulges under the skin which range in size from pea-sized to wide masses spanning a section of the abdomen or chest wall. They usually feel somewhat spongy and are freely moveable under the skin. They may grow very slowly, or not at all once they appear. You should always carefully monitor any mass or tumor on your pet’s body, including lipomas.
Have your pet examined by a veterinarian, if any of the following occurs:
The tumor is growing rapidly.
The tumor, after a long period of no growth, has suddenly started to grow again.
The tumor begins to change its appearance. It was formerly soft and now is hard. Or was formerly smooth and circular and now is beginning to grow nodular and lumpy.
The tumor is beginning to interfere with walking or movement, which may happen if the lump is near the hip or elbow.
The tumor is in a location where any growth will cause it to either be difficult or impossible to remove such as on the paw or leg.
Your pet is biting at the tumor and causing it to become infected or bleed.
In these cases, your veterinarian will probably suggest that the tumor be either biopsied or removed altogether.

Diagnosis:
Any visible tumor or mass should be shown to a veterinarian to rule out the possibility of a cancerous mass. Lipomas are usually quickly diagnosed by obtaining a small sample of cells with a syringe and viewing them under the microscope. Sedation is rarely necessary to obtain a cell sample.

Treatment:
Most lipomas are left untreated because they pose few health risks. However, very large or unsightly tumors may be surgically removed.