Squamous Cell Carcinoma in Dogs: UV and Skin Cancer

By Emiel Maddens  ·  Reviewed in consultation with licensed veterinary professionals  ·  Updated June 2026  ·  10 min read

Photo by Anya Prygunova on Unsplash

Squamous cell carcinoma (SCC) is a malignant tumor that arises from the squamous epithelial cells (keratinocytes) that form the outermost layers of the skin, mucous membranes, and nail bed. Among canine skin cancers, SCC ranks as one of the most frequently diagnosed, accounting for approximately 5% of all cutaneous tumors in dogs. The biological behavior of SCC varies considerably depending on the anatomical location of the tumor, with some forms being locally invasive but rarely metastatic while others carry a significant risk of spreading to regional lymph nodes and distant organs. Understanding the different presentations of canine SCC is essential for early recognition, appropriate diagnostic workup, and optimal treatment planning.

The relationship between ultraviolet (UV) radiation and cutaneous SCC is well established in dogs, paralleling the association observed in humans. Dogs with lightly pigmented skin, sparse hair coverage, and significant cumulative sun exposure are at highest risk for developing UV-induced SCC. The ventral abdomen, groin, medial thighs, and nasal planum are the most commonly affected sites because these areas receive the most intense reflected UV radiation and have the least protective pigmentation and hair coverage. Breeds with white or lightly colored coats and pink skin, such as Dalmatians, Bull Terriers, Pit Bull Terriers, and Beagles, are disproportionately at risk, particularly in geographic regions with high UV indices.

Beyond the UV-induced cutaneous form, SCC also occurs in locations where sun exposure is not a contributing factor. Nail bed SCC is the most common tumor of the canine digit and presents a distinct clinical entity with its own diagnostic and therapeutic challenges. Oral SCC, arising from the gingival or sublingual epithelium, is an aggressive tumor with a more guarded prognosis. Each form of SCC requires specific diagnostic and treatment approaches, and the prognosis varies significantly based on the tumor's location, size, and stage at the time of diagnosis. Early detection through regular skin examination and prompt veterinary evaluation of any suspicious lesion offers the best opportunity for successful treatment.

UV-Induced Cutaneous Squamous Cell Carcinoma

Pathogenesis of Solar Damage

UV-induced SCC develops through a progression of solar damage that accumulates over the dog's lifetime. Chronic UV exposure causes direct DNA damage in epidermal keratinocytes, producing pyrimidine dimer mutations that, if not repaired, can lead to uncontrolled cell proliferation. The earliest clinical sign of solar damage is actinic keratosis, characterized by reddened, scaly, and sometimes crusted patches on sun-exposed skin. These precancerous lesions represent a field of damaged cells from which SCC can eventually emerge. Dogs with established actinic keratosis are at significantly elevated risk for developing invasive SCC and should be monitored closely and protected from further UV exposure.

Clinical Presentation

UV-induced cutaneous SCC typically presents as a raised, firm, often ulcerated mass on sun-exposed skin. Early lesions may appear as non-healing sores, crusted plaques, or small nodules that bleed intermittently. Advanced tumors can become large, crater-like ulcers with raised, rolled borders and a necrotic center. The ventral abdomen and groin are the most common locations, where reflected UV radiation from ground surfaces strikes the sparsely haired, lightly pigmented ventral skin. Nasal planum SCC presents as crusting, depigmentation, and progressive ulceration of the nose, often initially mistaken for sunburn or an immune-mediated condition.

Breeds at Highest Risk

Several breeds are predisposed to UV-induced SCC due to their coat and skin pigmentation characteristics. Dalmatians, with their white base coat and tendency to develop large areas of unpigmented skin, are particularly vulnerable. Bull Terriers, American Staffordshire Terriers, and Pit Bull Terriers with white or predominantly white coats face similar elevated risk. Beagles, Basset Hounds, and Whippets with lightly pigmented ventral skin are also commonly affected. Any dog with pink, unpigmented skin in sun-exposed areas, regardless of breed, is potentially at risk for UV-induced SCC, especially in sunny geographic regions.

Nail Bed Squamous Cell Carcinoma

Clinical Presentation of Digital SCC

Nail bed SCC is the most common tumor of the canine digit, accounting for the majority of digital tumors in dogs. The condition typically presents with swelling of a single toe, loss or deformation of the associated nail, and varying degrees of lameness. Owners may first notice the dog licking excessively at one toe or a nail that appears to have fallen off without obvious trauma. As the tumor grows, the affected digit becomes progressively swollen, painful, and may develop secondary bacterial infection that produces purulent discharge. The insidious onset and initial resemblance to a simple nail injury or infection frequently leads to delayed diagnosis, with many cases having been treated for presumed infection for weeks before the correct diagnosis is established.

Breed Predisposition and Dark Nails

A striking epidemiological feature of nail bed SCC is its strong predilection for large breed dogs with dark-colored nails. Labrador Retrievers, Standard Poodles, Giant Schnauzers, and Rottweilers are among the most commonly affected breeds. Research has identified a possible association between melanin content in the nail bed and SCC development, though the mechanism is not fully understood. Unlike UV-induced cutaneous SCC, nail bed SCC is not associated with sun exposure, and the pathogenesis may involve chronic mechanical trauma, chronic inflammation, or breed-specific genetic susceptibility factors.

Diagnostic Approach and Staging

Radiographs of the affected digit typically reveal bone lysis (destruction) of the third phalanx (P3), which helps distinguish SCC from infectious causes of toe swelling. Fine needle aspirate cytology or incisional biopsy confirms the diagnosis. Staging evaluation for nail bed SCC includes thoracic radiographs or CT to evaluate the lungs for metastatic disease, and assessment of regional lymph nodes through palpation, fine needle aspirate, or sentinel lymph node mapping. Metastatic rates for nail bed SCC are reported at approximately 5% to 20%, with the lungs and regional lymph nodes being the most common metastatic sites.

Veterinary evaluation of any non-healing skin lesion is critical for early cancer detection.

Photo by Tima Miroshnichenko on Pexels

Staging and Prognostic Factors

TNM Staging System

Squamous cell carcinoma staging follows the TNM (Tumor, Node, Metastasis) system that classifies tumors based on the primary tumor size and invasiveness (T), involvement of regional lymph nodes (N), and presence of distant metastasis (M). Stage I tumors are small (less than 2 cm) and superficially invasive, Stage II tumors are larger (2 to 5 cm) or moderately invasive, Stage III tumors involve regional lymph nodes, and Stage IV tumors show distant metastasis. Each progressive stage carries a more guarded prognosis, underscoring the importance of early detection when tumors are still small and localized.

Location-Dependent Prognosis

The prognosis for canine SCC varies dramatically depending on tumor location. Cutaneous SCC of the trunk and limbs generally carries a favorable prognosis with wide surgical excision, as these tumors tend to be locally invasive but have low metastatic rates (less than 20%). Nail bed SCC has a variable prognosis: when treated with digit amputation at an early stage, many dogs achieve long-term disease-free intervals. Nasal planum SCC can be locally aggressive and may require radiation therapy in addition to or instead of surgery. Oral SCC, particularly sublingual and tonsillar SCC, carries the most guarded prognosis due to high metastatic rates and the difficulty of achieving complete surgical excision in the oral cavity.

Histological Grade

The histological grade of the tumor, determined by the pathologist evaluating the biopsy or excision specimen, provides additional prognostic information. Well-differentiated SCCs, which closely resemble normal squamous epithelial tissue under the microscope, tend to behave less aggressively than poorly differentiated tumors. The degree of local invasiveness, presence of lymphovascular invasion (tumor cells within blood or lymphatic vessels), and the mitotic rate (how quickly tumor cells are dividing) all influence the likelihood of local recurrence and metastatic spread. This information helps the veterinary oncologist develop an individualized treatment and monitoring plan.

Treatment Options

Surgical Excision

Wide surgical excision with clean margins is the primary treatment for most forms of canine SCC and provides the best chance of cure for early-stage tumors. For cutaneous SCC, a margin of at least 1 to 2 centimeters of apparently normal tissue around the tumor is recommended to ensure complete removal. Nail bed SCC is treated with amputation of the affected digit at the level of the third or second phalanx, and most dogs adapt well to the loss of a single digit with minimal long-term impact on mobility. Nasal planum SCC may require partial or complete nose amputation (nasal planectomy), which, while cosmetically significant, is typically well-tolerated by dogs.

Radiation Therapy

Radiation therapy plays an important role in the management of SCC, particularly for tumors that cannot be completely removed surgically or for which surgery would produce unacceptable functional or cosmetic outcomes. SCC is generally considered a radiation-responsive tumor type, and definitive radiation protocols can achieve local tumor control rates of 50% to 80% depending on tumor size and location. Radiation may be used as a sole treatment for inoperable tumors, as adjunctive therapy after incomplete surgical excision, or as a palliative treatment to reduce tumor size and improve quality of life in advanced cases.

Additional Treatment Modalities

For advanced or metastatic SCC, additional treatment modalities may be employed alongside surgery and radiation. Chemotherapy has limited efficacy against SCC compared to some other tumor types but may be considered for cases with confirmed metastatic disease. Non-steroidal anti-inflammatory drugs (NSAIDs), particularly piroxicam and meloxicam, have demonstrated anti-tumor activity against SCC in some studies and may be used as adjunctive therapy. Photodynamic therapy, electrochemotherapy, and intralesional chemotherapy are emerging treatment modalities that show promise for select SCC cases, particularly superficial tumors that are not amenable to conventional surgery.

Sun Protection for At-Risk Dogs

Identifying At-Risk Dogs

Dogs at highest risk for UV-induced SCC share several characteristics: lightly pigmented (pink) skin in sun-exposed areas, sparse hair coverage over these areas, and living in geographic regions with high UV indices. Dogs that spend significant time outdoors, particularly during peak UV hours (10 AM to 4 PM), accumulate UV damage more rapidly than indoor dogs. Owners of at-risk breeds should examine their dog's ventral abdomen, groin, and nasal planum regularly for any signs of solar damage, including redness, scaling, crusting, or non-healing sores.

Practical UV Protection Strategies

Effective sun protection for at-risk dogs involves multiple complementary strategies. Limiting outdoor exposure during peak UV hours reduces the most intense radiation exposure. Providing shaded areas in yards and outdoor spaces allows dogs to enjoy time outside while avoiding direct sun. UV-blocking dog clothing, including lightweight sun shirts and belly bands, provides physical protection for vulnerable skin areas. Pet-safe sunscreen formulated without zinc oxide (which is toxic if ingested) can be applied to exposed skin areas, including the nose, ears, and ventral abdomen, although frequent reapplication is needed as dogs tend to lick off topical products.

Managing Actinic Damage

Dogs that have already developed actinic keratosis, the precancerous sun damage that precedes SCC, require vigilant monitoring and aggressive sun protection to prevent progression to invasive cancer. Regular veterinary skin examinations, ideally every 3 to 6 months, allow early detection of any lesions progressing toward malignancy. Suspicious areas should be biopsied to distinguish actinic keratosis from early SCC. Topical treatments including imiquimod cream and 5-fluorouracil may be used under veterinary guidance to treat localized areas of actinic damage, though these medications require careful application and monitoring to prevent toxicity.

Living with a Diagnosis of SCC

Post-Treatment Monitoring

Following treatment for SCC, regular monitoring is essential for early detection of local recurrence or metastatic disease. Monitoring schedules typically involve physical examinations every 2 to 3 months for the first year after treatment, then every 4 to 6 months thereafter. Thoracic radiographs are performed periodically to screen for pulmonary metastasis. Regional lymph nodes should be palpated at each visit and aspirated if enlargement is detected. For nail bed SCC, monitoring also includes examination of the remaining digits, as multiple digit involvement can occur, though typically not simultaneously.

Quality of Life Considerations

Most dogs treated for early-stage SCC enjoy an excellent quality of life after treatment. Dogs that undergo digit amputation for nail bed SCC adapt remarkably well, typically returning to normal activity levels within a few weeks of surgery. Dogs that undergo nasal planectomy for nasal planum SCC similarly adapt well despite the cosmetic change. Quality of life assessment should be an ongoing process throughout treatment and monitoring, with the veterinary team and owner working together to ensure that the dog's comfort, mobility, and enjoyment of life are maintained.

Early detection remains the single most important factor in achieving a favorable outcome for dogs with SCC. Regular skin examinations, prompt veterinary evaluation of any suspicious lesion, and sun protection for at-risk dogs all contribute to the early diagnosis that allows the most conservative and effective treatment approaches. Working with a veterinary oncologist when SCC is diagnosed ensures access to the full range of treatment options and the expertise needed to develop an optimal management plan.

Squamous Cell Carcinoma in Dogs FAQ

Q: Is squamous cell carcinoma fatal in dogs?

The prognosis for canine SCC depends heavily on the tumor's location and stage at diagnosis. Early-stage cutaneous SCC treated with wide surgical excision carries an excellent prognosis, with many dogs achieving cure. Nail bed SCC treated with digit amputation also has a generally favorable prognosis. However, oral SCC, particularly sublingual and tonsillar forms, carries a more guarded prognosis due to higher metastatic rates. Early detection and prompt treatment significantly improve outcomes across all SCC types.

Q: Can dogs get sunburned?

Yes, dogs with lightly pigmented, sparsely haired skin can experience sunburn, particularly on the ventral abdomen, nose, ears, and around the eyes. Repeated sunburn contributes to cumulative UV damage that increases the risk of SCC development. Dogs with white or light-colored coats and pink skin are most vulnerable. Sun protection measures, including limiting midday sun exposure, providing shade, and using pet-safe sunscreen, help reduce this risk.

Q: What does squamous cell carcinoma look like on a dog?

SCC can present in various forms depending on location. Cutaneous SCC often appears as a raised, firm nodule or a non-healing ulcer with raised borders on sun-exposed skin. Nail bed SCC presents as swelling of a single toe with nail loss or deformity. Nasal SCC shows as crusting, depigmentation, and ulceration of the nose. Any persistent, non-healing skin lesion, particularly on lightly pigmented skin, should be evaluated by a veterinarian.

Q: Can squamous cell carcinoma spread to other parts of the body?

Yes, SCC can metastasize (spread), though the risk varies by location. Cutaneous SCC of the trunk has a relatively low metastatic rate (under 20%). Nail bed SCC has a variable metastatic rate of 5% to 20%. Oral SCC, particularly tonsillar, has the highest metastatic rate, exceeding 70% in some studies. Staging evaluation with radiographs and lymph node assessment helps determine whether spread has occurred.

Q: How can I protect my white-coated dog from skin cancer?

Key protective strategies include limiting sun exposure during peak UV hours (10 AM to 4 PM), providing abundant shade in outdoor areas, using UV-blocking dog clothing to cover vulnerable skin areas, and applying pet-safe sunscreen (avoiding zinc oxide products) to exposed skin. Regular skin examinations help detect early solar damage or suspicious lesions. If your dog has already developed actinic keratosis (precancerous sun damage), more frequent veterinary monitoring is recommended.

Sources

Goldschmidt, M.H., Hendrick, M.J. (2002). Tumors of the skin and soft tissues. In Meuten, D.J. (Ed.), Tumors in Domestic Animals, 4th ed. Iowa State Press.

Wobeser, B.K., et al. (2007). Diagnoses and clinical outcomes associated with surgically amputated canine digits submitted to multiple veterinary diagnostic laboratories. Veterinary Pathology, 44(3), 355-361.

Bronden, L.B., et al. (2009). The prognostic value of histological grading of canine squamous cell carcinoma. Veterinary Pathology, 46(1), 72-79.

Gross, T.L., Ihrke, P.J., Walder, E.J., Affolter, V.K. (2005). Skin Diseases of the Dog and Cat, 2nd ed. Blackwell Publishing. Chapters on neoplastic diseases.

Nikula, K.J., Benjamin, S.A., Angleton, G.M., Saunders, W.J., Lee, A.C. (1992). Ultraviolet radiation, solar dermatosis, and cutaneous neoplasia in Beagle dogs. Radiation Research, 129(1), 11-18.

Henry, C.J., et al. (2005). Clinical outcome of dogs with appendicular squamous cell carcinoma treated with limb amputation: 42 cases (1993-2004). JAVMA, 227(8), 1295-1297.

Related Reading

• Mast Cell Tumors in Dogs, The most common malignant skin tumor in dogs
• Melanoma in Dogs, Understanding this pigmented tumor and treatment approaches
• Histiocytoma in Dogs, Benign tumors that resolve spontaneously in young dogs
• Skin Tags and Warts, When skin growths warrant veterinary attention
• Understanding Skin Biopsy Results, How pathology reports guide cancer diagnosis

Emiel Maddens

Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.