Squamous Cell Carcinoma in Cats

Key Takeaways

Squamous cell carcinoma (SCC) is a cancer of the flat cells that line many tissues in cats, such as the skin, mouth, and esophagus. 

• SCC occurs most commonly where hair is sparse or light-colored as there is less protection from UV rays

• Typically, SCC is found on the ears, nose, lips, inside the mouth, and at the nail beds

• The characteristic symptom is a small, rough sore on the surface of the skin or membrane

• Immediate veterinary attention is required since early detection is crucial to good outcomes

• Diagnosis requires biopsy

• If the tumor is caught in the early stages, treatments include radiation, chemotherapy, and surgical excision

• Later stages usually impact quality of life, resulting in euthanasia

• Prevention is possible by reducing sun exposure and maintaining regular dental and veterinary health checks

A Closer Look: What is SCC in Cats?

Developing cancer is uncommon in cats, with squamous cell carcinoma being the second most common cancer in this species. Common locations for squamous cell carcinomas include the skin,  mouth, and nasal sinuses. In some cases, SCCs can develop in the lungs. 

The severity of SCC depends on how far the cancer has progressed before it is treated. Early stages are characterized by discrete, individual tumors that have not grown deeply and have not spread to other tissues. Later stages are characterized by deep invasion into the skin or mucous membrane, spreading to other tissues and metastasizing to other structures in the body.

In cases where SCC is detected early, treatment is straightforward and often curative. Left untreated, squamous cell carcinoma progresses, often spreading to other organs in the body. Once this has occurred, treatment is more complex and prognosis is poor.

Risk Factors

Cats with light-colored or patchy fur, particularly those who spend a lot of time outside or in sunlight, and cats with underlying conditions like papillomavirus, are most at risk. Older cats are more susceptible than young ones. 

In rare cases, two or more skin tumors occur in different locations on the body at the same time. This is called multicentric SCC, Bowen’s disease, or Bowenoid carcinoma. 

Cats who chew, bite, lick or scratch at affected areas are at risk of causing injury and infection.

Possible Causes

Squamous cell carcinoma is a cancer of the flattened cells that line external organ structures such as the skin, mouth, and esophagus. SCC develops when the DNA of the cells is damaged, causing cells to proliferate and form a tumor. 

Many cases of SCC are related to exposure to ultraviolet light. UV radiation is directly damaging to DNA. These tumors are most commonly seen on the tips of the ears, the nose, and the lips.

Cases of oral SCC are often related to chronic inflammation or dental disease.

Cases of SCC at the nail beds are often offshoots of lung cancer. The connection between the toes and the lungs is known as the lung-digit syndrome.

Main Symptoms

Most squamous cell carcinomas in cats noticed at home are found on the skin or nail beds. The symptoms of early-stage SCC of the skin are small sores. Other signs of skin or nail bed SCC include:

• Scabby, reddened, raised growths that may have a cauliflower-like appearance

• Masses that ooze or are ulcerated 

• Hair loss surrounding the mass

• Swelling of the skin surrounding the mass

Oral SCC symptoms can sometimes be mistaken for dental disease or other diseases of the mouth. They include:

• Masses, ulcers, or reddened areas on the upper or lower jaw, tongue, gums or tonsils

• Increased saliva production and drooling • Swelling of the jaw

• Loss of appetite • Weight loss

Nasal sinus SCC symptoms include:

• Ongoing runny nose • Occasional bloody nose • Excessive sneezing

• Tearing • Bad breath • Bulging eyes 

• Changes to the shape of the nose

Lung SCC symptoms include:

• Ongoing cough • Coughing up blood • Lethargy

• Exercise intolerance • Lameness if the tumor spreads to the paws (lung-digit syndrome)

• Rapid breathing • Weight loss

Testing and Diagnosis

Cats with small, scabby bumps on their ear tips, nose, lips, or toes, as well as cats with lesions in their mouths, require immediate veterinary care. Diagnostic tools include:

• Physical examination

• Fine needle aspiration

• Biopsy

• X-rays and ultrasounds

If the diagnosis is SCC, it is often recommended to determine which stage the cancer is in. Staging tools include:

• Blood work • Urinalysis • X-ray and ultrasound

Steps to Recovery

Referral to a veterinary oncologist is possible to determine the most effective treatment routes.  Early stage SCC is treated with:

• Cryosurgery (freezing the tumor) • Surgical excision 

• Radiation • Chemotherapy  • Pain medications 

• Antibiotics if secondary infections develop

Late stages of SCC are more complex. Additional treatments include:

• Debulking (removing part of the tumor to help preserve function of the underlying structure)

• Amputation of the affected area, in the case of SCC of the nail bed or of part of the nose 

• Immune-response modifiers 

Treatment of late stage SCC aims to slow the cancer’s progression and improve quality of life. Since it is not curative, euthanasia is sometimes the best option for these cases. 

SCC is a progressive disease. If it is detected early and treated appropriately, prognosis is good.  In cases where the cancer is not detected until later stages, especially where metastasis has occurred, the prognosis is poor.

Prevention

Limiting UV exposure by keeping cats indoors during daylight hours and by using UV protectant shades on windows where cats spend their time is recommended. 

Routine veterinary check ups are helpful to detect SCC early. Routine dental check-ups conducted annually are equally important, particularly in senior cats.

Is SCC Common in Cats?

Squamous cell carcinoma is the second most common type of cancer in cats.

Typical Treatment

• Surgery

• Radiation

• Chemotherapy