Abbreviated: SCC

Definition

Squamous cell, a flat scaly cell that is of epithelial origin. Squamous cell carcinoma is a metastatic lesion.

Clinical Signs

• A slightly elevated lesion with or without a cutaneous horn (outgrowth of tough protein substance called keratin).
• Swelling and interference with function (e.g., mobility, chewing, etc.) depending on location, and as growth advances.

*Note: for information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

Squamous cell carcinoma is a malignant type of growth that can metastasize either locally or systemically. It arises both on the skin and in mucous membranes, and may develop from an already present ulcerated area. A lesion may appear rough and scaly and its border wide with signs of swelling and inflammation.
Infections can accompany a lesion particularly if located in and around an area where the rat is likely to be able to scratch.

Common sites for squamous cell carcinoma are the face, jaw, inner ear canal, and near the base of the ear involving the Zymbal’s gland; the auditory sebaceous gland in rats. However, it can arise in other areas of epithelial tissue (e.g., the tail) and mucous membranes.

The prognosis for this type of cancer, depending upon the area involved, is extremely poor.

Figures

Case Histories Involving Squamous Cell Carcinoma

• Fig. 1: Squamous ca of the jaw in male rat (Bob)
• Fig. 2: Squamous ca involving Zymbal’s gland in male rat (Ramekin)
• Fig. 3: Squamous ca of the eye
• Fig. 4a: Squamous ca of the inner ear canal with ulceration, abscess, and infection (Jet’s case history). Includes link to cleaning of wound and supplies used.
• Fig. 5: Squamous ca involving Zymbal’s gland in female rat (Lauren). *Warning– graphic.*
• Fig. 6: Exophytic squamous cell carcinoma: preputial mass in male rat (Remus). *Warning– graphic.*

Diagnostics

A lesion or growth which may show biologic activity that includes a change in shape, size, color, or a bleeding ulceration.

A radiologic exam may be useful.

When attempting to excise, debulk, or debride, tissue may appear to have white fibrous strands or be of white powdery substance.

Histologic examination or cytology for cell type.

Treatment

Excise and remove if possible.

Scraping or debulking of tumor for comfort, if complete excision is not feasible.

Wound drain placement for removal of pus or fluid build-up if determined to be beneficial.

If infection is present, treatment with broad-spectrum antibiotics recommended.
Refer to the Rat Medication Guide for information on medications.

Rats do experience pain with surgical procedures. The type of pain medication used post-op should be determined based on extent of procedure and the anticipated severity of pain.

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.
  

• *Note: for pain not controlled by the use of an NSAID (e.g., Banamine, meloxicam, or carprofen), alone, consider alternating or co-administering with a narcotic (e.g., buprenorphine or butorphanol) or narcotic-like (e.g., tramadol) medication.

Palliative Care

Provide pain medication if: rat exhibits signs of pain, lesion is in advanced stage, or if the rat is not physically able to tolerate surgery. A nonsteroidal anti-inflammatory agent (e.g., Metacam or piroxicam); or a corticosteroid such as dexamethasone or prednisone may be included to help reduce inflammation and swelling of surrounding tissue.

*Note of interest: some forms of cancer such as SCC appear to exhibit COX-2 activity. Studies suggest that an NSAID, such as piroxicam, may have anti-tumor effects besides their anti-inflammatory effects. This may make them useful depending on the location and extent of the cancer.

Refer to Rat Medication Guide for information on medications.

*Note: Always check with a veterinarian when giving any medications to determine appropriate use or contraindication.

Euthanasia should be considered if tumor growth affects quality of life.

Nursing Care

• Provide hospital cage during recovery, or if there are concerns that the rat’s 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 product 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.
• Give medications as prescribed by veterinarian.
• In the event of dried or excess drainage, the incision site may be cleaned with a moistened Q-tip (swab), using warm water or normal saline.
• Contact veterinarian if any of the following develop: swelling, redness, increased pain at the incision site, or there are signs of increased weight loss, lethargy or changes in habits.
• Assess nutritional status:
  • Provide fluids to prevent dehydration. If the rat is willing to drink on its own or by syringe (using needless syringe), the following are suggested: fresh water, or a glucose mixture of 3 teaspoons of honey in 1 pint of warm water (be sure water is warm enough to dissolve honey and then cooled just enough so as not to burn rat’s mouth), or 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.
  • Care should be taken to prevent aspiration when giving fluids with an oral syringe. If the rat is not drinking discuss providing warmed SQ fluids with your vet.
  • For 24 to 48 hrs post-op, feed iron-rich foods to prevent anemia (cooked liver, scrambled or hard-boiled eggs).
  • Provide additional nutritional supplement, such as soy baby formula, Ensure, Boost, NutriCal paste (for dogs and cats found in pet store), mashed avocado, and baby foods. If the rat is not willing to eat on its own, provide feeding in an oral needless syringe every 2 hours being careful to prevent aspiration. Providing small amounts of food in this fashion will help to promote intestinal motility during illness. Include multi-vitamin supplement (can be found in pet store) if food intake is poor.
  • It may be necessary to provide softer or puree foods, or baby foods for those rats with jaw involvement.
• Assist rat with grooming and cleaning if needed.
• If condition continues to deteriorate and precludes further comfort or quality, discuss euthanasia with veterinarian.

Outcome

• A reduction in pain and swelling of surrounding tissue.
• The incision site is free from infection.
• Increase of comfort and mobility.
• Preserve the quality of life.
• Emotional support for those having to consider euthanasia for their rat.

Prevention

• Physical assessment of rat for injuries and obtain early treatment for abrasions, bites, lesions or growths.
• Early detection of and treatment of growth, while still limited, improves quality of life.