Basal cells are found underneath the upper layer of the skin, i.e. the epidermis. A basal cell tumor is simply a benign growth of these cells, but a basal cell carcinoma is a malignant growth of the cells.
Canine basal cell tumors usually develop in middle-aged and elderly dogs, forming on the neck, head (especially the ears), and forelimbs. The most predisposed breeds are Kerry Blue and Wheaten Terriers, and Wirehaired Pointing Griffons. These tumors usually take the form of hard, raised, solitary, dome-shaped lumps; often being hairless or ulcerated. They tend to be dark in colour. The tumors may stand out like stalks from the surface of the skin, varying in diameter from less than 0.4 inches (1 cm) to more than 4 inches (10 cm). Though benign, basal cell tumors can be huge and may lead to widespread secondary inflammation and ulceration. They may break the skin, drain fluid or pus, and result in skin tissue death. All these effects make the dog uncomfortable, necessitating surgical removal of the tumor, thus lessening the possibility of inflammation and secondary infection.
Basal cell carcinomas tend to affect more cats than dogs, appearing as ulcers on the neck, head, and legs of elderly dogs. In contrast to benign basal cell tumors, basal cell carcinomas are not normally raised beyond the surface of the skin. Nevertheless, they increase and create new ulcers. As a result, surgical removal is necessary. The most affected breeds are Saint Bernards, Norwegian Elkhounds, and Scottish Terriers. Basal cell carcinomas can form roughly anywhere on the body, in contrast to basal cell tumors. Although these tumors spread to neighbouring skin, they rarely spread to other organs. The preferred mode of treatment is surgical removal. During surgery, the veterinarian removes some normal skin around the tumor, ensuring that the entire tumor has been taken out.
Benign Fibroblastic Tumors
Benign masses of fibrous proteins (collagen) are known as Collagenous nevi. They are commonly found in middle-aged or older dogs, with the head, legs, and neck areas being the most vulnerable to trauma. The tumors can appear as flat or raised lumps that grow in the skin or fat underneath the skin. It is possible to efficiently treat both forms by surgical removal. However, there are rare cases where some become too large to be removed via surgery.
Skin tags are unique, benign, lumps on the skin of elderly dogs. They are mostly found in large dog breeds, though any breed may be affected. Skin tags can appear in clusters or as a single lump. They usually appear as long, stalk-like growths, frequently enclosed by a wart-like surface. The best way to verify a diagnosis is to perform a biopsy, though surgical removal is non-compulsory.
Fibromas look a lot like skin tags or collagenous nevi. Though all breeds can be affected, old dogs are the primary victims of fibromas, with Golden Retrievers, Boxers, and Doberman Pinschers being the most prone. Fibromas emerge as hairless, isolated, raised lumps originating under the skin of the head and legs. They can either be spongy and soft (fibroma molle) or hard and rubbery (fibroma durum). Such tumors may not require treatment, as they tend to be benign. Nevertheless, total removal via surgery should be done as the tumor may get very big.
Benign, Non-viral, Wart-like Tumors
Contrary to their name, these tumors are not really warts, though they may resemble them. They are simple to remove and are not really big health threat to the dog.
Canine warty dyskeratomas are uncommon, benign tumors that develop close to hair follicles or sweat glands. They look like lumps with a dark spot in the middle. How they are created is unknown, and is typically treated surgically.
Epidermal hamartomas (nevi) are darkened, pointed lumps on the surface of the skin, frequently growing in a line. Though quite rare, the disease is hereditary in Cocker Spaniels, especially puppies. Although they are benign, they look unpleasant and are susceptible to secondary bacterial infection. As such, epidermal hamartomas should be treated or removed, while minor hamartomas may be removed surgically. Big or compound hamartomas might respond to medical treatment.