Squamous Cell Carcinoma in Cats
Squamous cell carcinoma (SCC) is a tumor that affects the cells of the skin. The skin is composed of several layers of cells. The squamous layer is located in the epidermis, which is the outermost part of the skin. Since the SCC develops from squamous cells, it can occur anywhere in the body where squamous cells are present. Thus, SCC may be found in the tip of the cat’s ears (pinnae), nose, nail bed, and corners of the eyes. Continue reading to learn more about how squamous cell carcinoma is recognized and treated in cats.
What do Squamous Cell Carcinomas look like?
Squamous cell carcinoma is the thirst most common type of skin tumor of cats, following basal cell tumors and mast cell tumors.
Squamous cell carcinomas usually develop as solitary lesions. But there is the so-called multicentric SCC in which two or more lesions develop in multiple locations on the cat’s body, including inside the mouth. Multicentric SCCs are also called ‘Bowen’s disease or Bowenoid carcinoma. Cases of multicentric SCCs in cats are rare. Only about a third of cats diagnosed with cutaneous SCC have multiple lesions.
How do cats develop Squamous Cell Carcinoma?
Most cases of SCCs in cats are caused by a mixture of risk factors that include genetic and environmental factors.
Environmental factors include exposure to ultraviolet (UV) rays of the sun, chemicals, or specific viruses. The most common cause, however, is excessive sun exposure. The sun’s UV radiation damages the DNA of cats, triggering the cells to divide and multiply.
Bowen’s disease can affect even areas of the skin that are protected by hair. The condition is considered to be caused by a virus rather than exposure to the sun’s UV rays.
Light-colored or white cats are more predisposed to getting these tumors. There is, however, a decreased risk in Persians, Siamese, and Himalayan breeds.
Physical trauma or serious burns that damage the cells of the epidermis are also risk factors for SCC in cats.
Symptoms of Feline Squamous Cell Carcinoma
Squamous cell carcinomas usually occur in areas of the skin that are devoid of hair or with sparse hairs and are lightly pigmented. These tumors tend to localize and don’t spread to other sites from the original site of growth (metastasize). If a large area of the skin is exposed to the sun, multiple skin lesions may develop.
The tumors are usually found in areas of the body that are more exposed to sunlight, such as the edge of the nose, lips, and eyelids.
The appearance of SCC is highly variable. At first, it may appear like a scab or a spot on the skin that is red and thickened. The tumors may gradually become ulcerated. Tumors may appear raised, red, or have a cauliflower-like growth. Multicentric SCCs may develop on areas of the skin that are pigmented. They may appear ulcerated, painful, bleeding, and have a scabby appearance. Multicentric SCCs can reach a diameter of 1.5 inches.
Most cases of SCC in cats appear on the face. But it can also occur anywhere in the body, including the cat’s toes, usually in the nail bed. A tumor in the nail bed can cause lameness because of the pain and swelling. It may also lead to the loss of the nail. Affected cats may lick or chew at the area persistently which will eventually lead to self-inflicted trauma. Measures should be undertaken to prevent cats from licking or chewing the tumors to avoid further tissue damage and infection.
Diagnosis of Squamous Cell Carcinoma in Cats
To arrive at a definite diagnosis, a tumor biopsy is often performed by your vet. Fine needle aspiration (FNA) of cells from the tumor may also be done so the cells can be microscopically evaluated (cytology).
If the results of the FNA and cytology are not clear, a complete biopsy may be necessary. There is a need to put the patient under general anesthesia to prevent any problems during a biopsy. The procedure involves the removal of a portion of the tumor which is then microscopically examined (histopathology).
If the SCC occurs on the cat’s toe(s), radiographs (x-rays) can help in the diagnosis. The reason x-rays may be necessary is that about 90% of toe tumors in cats are actually cancer that has metastasized from the lungs. This is referred to as “lung-digit syndrome”. Chest x-rays can help determine if the toe tumor is secondary to lung cancer or a true SCC.
Staging of the Tumor
Since some SCC in cats may spread to the lung or adjacent lymph nodes, your vet may find it necessary to do staging.
Staging is highly recommended for tumors that are malignant because of their tendency to spread. The procedure includes urinalysis, lung X-rays, bloodwork, and abdominal ultrasound. Samples may be taken from adjacent lymph nodes to check if the tumor has spread.
Treatment Options for Squamous Cell Carcinoma in Cats
Like most tumors, it’s best to treat SCC when tumors are still small. Treatment options include the following:
Surgical removal - This option provides long-term control. In some cases, surgery can cure skin SCC. If the tumor is on the cat’s ear, pinnectomy (removal of the external ear flap) may be necessary. After surgical removal of the tumor, about 75% of cats diagnosed with multicentric SCC will experience the growth of new tumors in other parts of the body.
Superficial radiation therapy - This is indicated for multiple small tumors. It’s an effective treatment option that is well-tolerated by affected cats.
Topical medication - This is often used to treat Bowenoid carcinoma (Bowen’s disease).
Other treatment options include:
- Cryotherapy - the tumor cells are destroyed by freezing.
- Laser ablation
- Photodynamic therapy
- Chemotherapy
If your cat has been diagnosed with SCC, you should consult your vet for the pros and cons of the available treatment options. Following treatment, you should monitor your cat closely for signs of new skin lumps and bumps. Limiting your cat’s exposure to the sun may also prevent the development of more SCC.
If left untreated, the tumor will become gradually more ulcerated. There will be swelling in the area that is usually accompanied by tissue damage around the tumor as it invades the deeper parts of the skin and eventually metastasizes to other areas of the body.
An excellent prognosis generally follows surgery or radiation therapy. But if large, more invasive tumors are not surgically removed, the long-term prognosis is poor.
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