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Our star, the Sun, can induce cancerous change in the skin cells of humans as well as our pet cats and dogs. Long term ultraviolet light exposure is a known risk factor for development of skin cancers in white cats and lightly pigmented short haired breeds of dogs. The presumed reason is that white coats reflect instead of absorbing the sun’s rays and as a result these pets tend to sunbake for extended periods.

Cats

The nose and ears of white haired cats are the most common sites for the development of squamous cell carcinomas (SCC).  Initially the solar radiation causes a shallow crust like lesion followed by red firm plaques. In cats these tumours tend to appear erosive and ulcerative and instead of proliferating above the skin they invade the deeper structures in an inwards direction. Treatment is surgical (blade or cryo) and best done in the early stages of the disease. Prevention by keeping white cats as 100% indoor pets is preferred.

Dogs

The skin of the inner thighs and groin region is a common site for the development of two darkly pigmented skin cancers called melanoma and dermal hemangiosarcoma (HSA). Both appear as well defined dome shaped dark red to purple/black masses usually less than 5-10mm initially. Canine melanomas are predominantly benign (85%) but dermal HSA has a less predictable biological behaviour especially if it invades into the space below the skin called the subcutaneous space. Here the malignant vascular cancer spreads rapidly through the dog’s own blood vessels to the liver, lungs and brain. Treatment for both is initially surgical and best done in the early stages of the disease.

Owners should have any new pigmented skin lumps checked by fine needle aspirate biopsy by their vets. If they look like blood blisters remove them ASAP if they are pigmented skin cells they should be monitored and if growing or ulcerative removed surgically. Prevention is by keeping light coated dogs out of the sun during periods of high UV from puppyhood onwards.