Squamous cell carcinoma (SCC) is a common form of skin cancer affecting dogs. This malignant tumor originates from squamous cells, flat, scale-like cells found in the outermost layer of the skin, the epidermis. Early detection and proper management can significantly influence a dog’s outcome.
Recognizing Squamous Cell Carcinoma
Squamous cell carcinoma lesions often present as raised, firm masses or nodules on the skin. These lesions can appear red, inflamed, or covered in thickened, crusty skin. They may also resemble non-healing sores or warts and can sometimes ulcerate or bleed.
These tumors are frequently found in areas with thin hair or unpigmented skin, such as the nose, ears, abdomen, toes, nail beds, and scrotum. For example, a tumor on the toe or nail bed might cause a missing toenail, lameness, or pain around the feet. Consulting a veterinarian promptly for any suspicious skin changes is advised.
Causes and Risk Factors
Chronic exposure to ultraviolet (UV) radiation from sunlight is a primary factor increasing a dog’s risk for squamous cell carcinoma. This is especially true for dogs with light-colored or thin coats, which offer less natural protection against UV rays, and those spending significant time outdoors.
The canine papillomavirus has been implicated in some SCC cases. Chronic inflammation or non-healing wounds can also act as predisposing factors. Certain dog breeds, such as Dalmatians, Bull Terriers, Beagles, Bloodhounds, Keeshonds, and Standard Schnauzers, show a genetic predisposition. Older dogs, between 6 and 11 years of age, also have a higher incidence of SCC.
Diagnosis and Treatment Approaches
Diagnosis begins with a thorough physical examination by a veterinarian. A definitive diagnosis relies on a biopsy, which involves taking a tissue sample from the lesion. This sample is then sent for histopathological examination to confirm cancerous cells and determine the tumor type.
A fine needle aspirate (FNA) can provide a preliminary diagnosis, but a biopsy offers a more comprehensive assessment. For advanced cases or suspected metastasis, imaging techniques like X-rays or ultrasound may evaluate for spread to local lymph nodes or distant organs. This staging helps determine the cancer’s extent and guides treatment.
Surgical excision is the primary treatment for SCC, aiming for complete tumor removal. This often requires wide surgical margins, at least 2 centimeters around the visible tumor. For tumors on a toe, amputation of the affected digit may be necessary. Tumors on the nose or ear may require partial removal of those structures.
Radiation therapy is another treatment option, often used when surgical removal is incomplete or for tumors in difficult-to-access areas. Cryotherapy and photodynamic therapy can be considered for early-stage or superficial lesions. Electrochemotherapy may also be employed. Chemotherapy alone is less commonly effective for SCC but might be considered in advanced cases or as an adjunct to other therapies, especially if metastasis has occurred. Treatment strategy is tailored to the tumor’s size, location, invasiveness, and the dog’s overall health.
Prognosis and Prevention
The prognosis for dogs with squamous cell carcinoma varies, depending on the tumor’s location, size, and whether it has spread. Early diagnosis and complete surgical removal offer a good outlook. Tumors on the skin that are completely removed tend to have a favorable prognosis. However, SCC in certain locations, such as the nail bed, can be more aggressive and have a higher likelihood of spreading or recurring even after amputation. Tumors in the tonsils also tend to be aggressive with a poorer prognosis due to their tendency to spread to regional lymph nodes.
Preventing squamous cell carcinoma involves limiting a dog’s exposure to known risk factors. For at-risk dogs, especially those with light-colored or thin coats, limit sun exposure during peak UV hours (10 AM to 4 PM). Providing ample shade outdoors or using protective clothing, like UV-protective vests, can help. Applying pet-safe sunscreens to vulnerable, thinly haired, or unpigmented areas, such as the nose and ear tips, also offers protection. Regular home skin checks and routine veterinary examinations contribute to early detection.