Squamous Cell Carcinoma in Cats: Causes, Symptoms, Treatment, and Prognosis

Squamous Cell Carcinoma (SCC) is a type of skin cancer that commonly affects cats, particularly older ones. This aggressive malignancy arises from squamous cells in the outer layer of the skin and can also affect areas like the mouth, nose, and ears. While SCC is a serious condition, understanding its causes, symptoms, and treatment options can help cat owners make informed decisions to improve their pet’s quality of life and potentially extend their lifespan.

Causes of Squamous Cell Carcinoma in Cats

The exact causes of squamous cell carcinoma in cats are not fully understood, but there are several factors that have been linked to the development of this cancer:

1. Exposure to Ultraviolet (UV) Light:
   • Cats with lighter skin or those that spend a lot of time in direct sunlight are at a higher risk of developing SCC, particularly on sun-exposed areas like the nose, ears, and eyelids. UV radiation can damage the DNA in skin cells, leading to the development of cancer over time.
   • White or light-colored cats, such as the Domestic Shorthair or Siamese, are particularly prone to SCC due to their lack of protective pigmentation.
2. Chronic Irritation and Inflammation:
   • Long-term irritation, infections, or chronic wounds can contribute to the development of squamous cell carcinoma. Cats with recurring skin injuries or chronic inflammation in certain areas may develop cancerous growths over time.
3. Viral Infections:
   • Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are known to suppress a cat’s immune system. Cats with these viral infections may be more susceptible to developing various forms of cancer, including SCC.
4. Environmental Toxins:
   • Exposure to certain carcinogenic chemicals or environmental pollutants may increase the likelihood of a cat developing SCC. However, this is considered less common than UV exposure or chronic inflammation.

Symptoms of Squamous Cell Carcinoma in Cats

The symptoms of squamous cell carcinoma can vary depending on the location of the tumor. Common areas affected by SCC in cats include the nose, ears, mouth, and digits (toes). The most noticeable symptom is the appearance of abnormal growths or lesions on the skin or mucous membranes.

1. Skin (Nasal Planum, Ears, Eyelids)

• Lesions or Sores: Non-healing wounds or ulcers on sun-exposed areas such as the nose, ears, or eyelids are common. These sores may appear red, crusted, or scabbed and do not heal with typical treatment.
• Bleeding: The affected areas may bleed easily if scratched or disturbed.
• Swelling or Lumps: Raised, irregular lumps may form around the affected area. Over time, the tumor may grow and become more prominent.
• Hair Loss: The area around the lesion may experience localized hair loss.

2. Oral Cavity

• Difficulty Eating or Drooling: SCC in the mouth often presents with signs of oral discomfort, difficulty chewing, excessive drooling, or reluctance to eat.
• Foul Breath (Halitosis): An SCC tumor in the mouth can cause infections that lead to bad breath.
• Weight Loss: As eating becomes painful, cats may eat less and lose weight over time.

3. Paws (Nail Bed or Toes)

• Swelling of the Digits: Cats may develop swelling around the affected toe, accompanied by limping or discomfort when walking.
• Ulcers or Lesions: Non-healing sores may appear on the toes, resembling infections or other skin conditions.

Diagnosis of Squamous Cell Carcinoma in Cats

Early detection of squamous cell carcinoma can improve treatment outcomes, making it important for cat owners to monitor their pets for any abnormal growths or lesions. A veterinarian will typically follow these steps to diagnose SCC:

1. Physical Examination:
   • The vet will perform a thorough physical exam to evaluate the affected area, check for other abnormal growths, and assess the overall health of the cat. The appearance of non-healing wounds or suspicious lesions may immediately suggest SCC.
2. Biopsy:
   • A biopsy is the most definitive way to diagnose SCC. This involves taking a small sample of the lesion or tumor for microscopic examination. The pathologist will examine the cells to determine whether they are cancerous and, if so, confirm the diagnosis of squamous cell carcinoma.
3. Imaging:
   • In cases where the SCC is suspected to have invaded deeper tissues, such as bone, or metastasized (spread) to other parts of the body, imaging techniques like X-rays or CT scans may be recommended. This is especially common when SCC is found in the oral cavity or around the nose.
4. Fine Needle Aspiration (FNA):
   • In cases of lumps or swelling, the veterinarian may perform a fine needle aspiration to collect a small sample of cells for cytological examination. This is less invasive than a biopsy but may provide enough information for diagnosis.

Treatment Options for Squamous Cell Carcinoma in Cats

Treatment for SCC in cats depends on the location, size of the tumor, and whether the cancer has spread to other parts of the body. The primary goal of treatment is to remove or destroy the cancerous cells while minimizing pain and discomfort for the cat.

1. Surgery:

• Wide Surgical Excision: The most common and effective treatment for SCC is surgical removal of the tumor. In many cases, this involves removing not only the tumor but also a margin of healthy tissue to ensure all cancerous cells are eliminated. For tumors on the ears or nose, partial or complete removal of the affected area may be necessary.
• Toe Amputation: If SCC is present in the digits, amputation of the affected toe may be recommended to prevent further spread of the cancer.

2. Cryotherapy:

• Cryotherapy involves freezing the cancerous tissue with liquid nitrogen. This is typically used for smaller, superficial tumors, particularly on the skin. It is a less invasive option compared to surgery but is not effective for larger or deeper tumors.

3. Radiation Therapy:

• Radiation therapy is often used in cases where the tumor cannot be fully removed with surgery, or in cases where surgery is not feasible due to the location of the tumor. Radiation can help shrink tumors and relieve symptoms, especially for SCC in the nasal or oral regions. However, it may require multiple sessions and can be expensive.

4. Photodynamic Therapy:

• This is a newer treatment method that uses a light-sensitive drug and a specialized light to target and destroy cancerous cells. Photodynamic therapy is still not widely available but has shown promise for treating superficial skin cancers like SCC in cats.

5. Chemotherapy:

• Chemotherapy is generally not the first line of treatment for SCC, but it may be used in conjunction with surgery or radiation for more aggressive cases or when the cancer has metastasized. Chemotherapy drugs may also be used to manage inoperable tumors or provide palliative care to reduce pain and improve the cat’s quality of life.

6. Topical Therapy:

• In some cases, topical treatments like imiquimod (an immune response modifier) can be applied to small or early-stage SCC lesions on the skin. These treatments help stimulate the cat’s immune system to fight the cancerous cells and may be used in combination with other therapies.

Prognosis for Cats with Squamous Cell Carcinoma

The prognosis for cats with squamous cell carcinoma varies widely depending on several factors, including the tumor’s location, size, and stage at diagnosis.

Factors That Affect Prognosis:

• Tumor Location: Cats with SCC affecting the skin (particularly the ears or nose) tend to have a better prognosis if the tumor is detected early and surgically removed. In contrast, oral and nasal SCC often have a poorer prognosis due to the difficulty of complete surgical removal and the likelihood of local invasion into bones or other tissues.
• Tumor Size and Spread: Small, localized tumors that have not yet spread to other tissues are associated with a more favorable outcome. In cases where the cancer has metastasized to lymph nodes or other organs, the prognosis is typically worse.
• Response to Treatment: Cats that undergo successful surgery or radiation therapy may achieve long-term remission, though recurrence is possible. Early intervention typically leads to better outcomes.

General Prognosis:

• For Skin SCC: If treated early, cats with skin SCC can have a good prognosis, with many living for years following treatment. However, recurrence is possible, and regular monitoring is crucial.
• For Oral or Nasal SCC: The prognosis is often guarded to poor, with median survival times ranging from 3 to 6 months after diagnosis, even with aggressive treatment. Palliative care may be required to manage symptoms and maintain quality of life.

Preventing Squamous Cell Carcinoma in Cats

While it is impossible to completely prevent SCC, there are steps you can take to reduce your cat’s risk:

• Limit Sun Exposure: Keep cats indoors during peak sunlight hours, especially if they are light-skinned or have a history of skin issues.
• Use Sunblock: For cats that enjoy spending time outdoors, applying pet-safe sunblock to areas like the ears and nose can help protect against UV damage.
• Regular Veterinary Check-ups: Regular vet visits can help detect early signs of cancer or other skin abnormalities. Early detection is key to improving the chances of successful treatment.

Conclusion

Squamous cell carcinoma is a serious form of cancer in cats, but with early detection and appropriate treatment, some cats can achieve remission or enjoy a better quality of life. Understanding the causes, recognizing the symptoms, and seeking prompt veterinary care are crucial steps in managing this disease and giving your cat the best possible outcome.