Many dogs, particularly brown or liver-colored Labrador retrievers, some American pit bulls and all pharaoh hounds, sport light-brown noses and light-colored eye rims. A white- or light-haired dog can be genetically predisposed to have a pink or mottled nose. As a dog of any breed ages, owners may notice black spots growing and changing on the animal's nose and eyelids. While your dog's new spots may not be symptomatic of any disease, two types of skin cancer can show up as black lesions on the face, and you should seek a veterinary diagnosis to ensure your pet's continued health.
Heavy pigmentation often results in black spots, particularly those found on the nose and tongue of dogs, says Lisa Peterson, the American Kennel Club director of communications. Depending on the breed, your dog's "points" -- the nose, toe pads, toenails and eye rims -- may be colored light pink, brown or black. The melanin that gives the dog's skin and hair its dark color often bleeds over to lighter-skinned areas, creating random spotting.
Melanoma develops in the melanocytes -- the cells that manufacture pigment -- of dogs. A form of skin cancer, cutaneous melanoma typically presents as dark-colored tumors seen anywhere on the face, feet, trunk and scrotum of dogs. While black dogs may be predisposed to melanoma, this type of cancer also shows most commonly in Boston terriers, cocker spaniels, chow chows, boxers, Irish setters, springer spaniels, Scottish terriers, Doberman pinschers and Airedale terriers. Oral melanoma tumors affect the cells of the mouth and nose, can be both light and dark and can metastasize quickly to the dog's lungs and other organs.
Squamous Cell Carcinoma
Squamous cell carcinoma originates in the flat, epithelial cells that make up the outer skin cells of your dog's mouth, skin and nose. These cells form plate-like layers that also compose its gastrointestinal, urinary, respiratory and reproductive tracts. Squamous tumors can show as black, crusty lesions anywhere on the lips, nose and eyelids of white-faced dogs. Typically caused by over-exposure to the sun, this type of skin cancer invades the system rapidly and, because of placement, can be challenging to remove surgically. Often, a diagnosis of squamous cell carcinoma comes too late to allow for surgical intervention.
Diagnosis and Treatment
Veterinarians typically recommend running a full blood panel and taking a biopsy or fine needle aspirate of the spot to make an initial diagnosis. Depending on the location of the spots, radiographs of your dog's head and nasal passages may need to be taken to determine if there is evidence of internal tumor growth. If a cancerous tumor is suspected, treatment revolves around surgery on the tumor and a histopathologic examination of the tumor cells to define the cancer's exact cause. Your veterinarian may also suggest chemotherapy and radiation therapy as further treatment.