Definition

A fatty tumor that can sometimes be seen as multiples. This type of tumor is not metastatic.

Clinical Signs

• It can be felt as a soft, easily movable, subcutaneous nodule either on the shoulders, along the back, or on the extremities.

Etiology

Lipomas are slow growing, generally harmless, benign fatty tumors. These tumors are made up of normal, mature, fat cells surrounded by a thin fibrous capsule. The cause of lipomas is yet to be understood. It is believed that there is a familial or genetic link to the development of lipomas. It is also believed that minor injuries may trigger their growth. Lipomas can, in most cases, be easily removed through surgery when necessary.

While lipomas may occur anywhere on the body, they are seen most frequently in the subcutaneous tissues of the shoulders, back and extremities. Lipomas occur more often as a single nodule, but can occasionally develop as multiple nodules. Because these tumors are mostly benign (non-cancerous) harmless growths, they are highly unlikely to undergo malignant changes, and do not metastasize to other areas of the body. Hemorrhage and necrosis are rarely seen with lipomas.

Treatment is not usually required, unless there is a change noticed in the size or shape of the nodule. If this occurs it is recommended that the vet do a biopsy. Lipomas are primarily removed if they cause pressure, irritation, decrease in mobility for the rat, or if the tumor is continuing to grow.

Lipomas can sometimes have other tissue involvement such as connective tissue, blood or bone marrow. Although rare, malignant liposarcomas could occur. For this reason lumps suggestive of tumors should be evaluated and removed if necessary.

Figures

Case Histories of Lipoma In Rats

• Fig. 1: View of excised lipoma
• Fig. 2: Excised lipoma from adult male rat (Stat!)
• Fig. 3: Lipoma in a 30-month-old male rat (Badger)

Diagnostics

Assess the location, duration, firmness, and size.

A needle aspirate with histological examination or cytology as necessary.

Magnetic resonance imaging (if available for small animals) may be useful if suspecting additional tissue involvement.

Treatment

Excision and removal is recommended if tumor growth continues or tissue type is suspicious.

If surgery is required, the following is recommended for pain control post-op:

• For severe pain or first 24 hours post-op: Buprenex (buprenorphine), or Torbugesic (butorphanol).
  

• For mild to moderate pain: Banamine (flunixin meglumine), Metacam (meloxicam), or carprofen. Do not use if a corticosteroid has already been prescribed.
  

• For mild pain: Tylenol (acetaminophen) if no contraindications.

For information on above listed medications, refer to the Rat Medication Guide.

Nursing Care

• Provide hospital cage during recovery, or if there are concerns that their cage mates may groom sutures or wound site.
• Provide clean bedding daily such as felt, soft t-shirt type material or ink-free paper towels. Avoid using material such as terry cloth type towels that can ravel. Also avoid litter-type bedding, post-op, until healed to prevent the chance of wound contamination or infection.
• Provide additional warmth to maintain body temperature within normal limits. It is essential that the rat does not become overheated or dehydrated. The rat should also be able to move away from the heat source if it becomes uncomfortable. If the rat is unconscious or immobile extreme care must be taken to keep the heat low and stable.
  • You can use an isothermic product that is heated in the microwave such as SnuggleSafe®. Make sure to follow the product directions carefully and wrap in a towel before placing in the cage. SnuggleSafe® will provide heat for 12 hours before needing to be reheated. Other similar types of products may vary in re-heat time. Check directions for individual product.
  • If using a heating pad (good for long term use) use only the low heat setting, put a thick towel in between the pad and the cage bottom, and place beneath a corner of the cage.
  • If none of these options are available you can use a plastic bottle filled with hot water, and wrapped in a towel, in the corner of the cage.
• May require body wrap if thread sutures are used, to prevent rat from chewing.
• In the event of dried or excess drainage, the incision site may be cleaned with a moistened Q-tip (cotton swab), using warm water or normal saline.
• Medicate for pain as needed or as necessary.
• Assess nutritional status:
  • For 24 to 48 hrs post-op, feed iron-rich foods to prevent anemia (e.g., cooked liver, scrambled or hard-boiled eggs).
  • Provide additional high calorie foods or food supplements such as Nutri-Cal Paste, canned Ensure, soy or soy formula, during recuperation. Include multi-vitamin supplement (can be found in pet store) if food intake is poor.
  • Encourage fluid intake while recuperating, such as water, Jell-O water, or electrolyte replacement drinks such as Pedialyte or Gatorade (which can be found in local grocery stores). Please note that Pedialyte is only good refrigerated for 24 hours after opened, but can be frozen as ice cubes and thawed as needed.
    *Note: a juicy type of fruit also provides an additional fluid source in the diet.
• Contact veterinarian if any of the following are observed: swelling, redness, or pain at the incision site, or if there are signs of increased weight loss, lethargy, or changes in habits.

Outcome

• Pain relieved
• Incision site free from infection
• Increased comfort and mobility
• Increased quality of life

Prevention

• Attention is given to proper diet, and the prevention of obesity.
• Maintain a safe environment free of preventable injury.
• Early detection of the tumor while the growth is still small decreases operative time and enhances recovery period.