Basal Cell Tumors

skin_layers_basalcell_2018What is a basal cell tumor?

A basal cell tumor is an abnormal growth or mass resulting from the uncontrolled division of basal cells or cells from the sweat glands, hair follicles, or sebaceous glands. Basal cells make up the bottom (or basal) layer of the outermost layer of the skin, the epidermis. The basal layer is essentially the defensive layer of the epidermis. It contains many different types of cells, including those involved with inflammation.

Basal cell tumors are one of the most common skin tumors in dogs and cats. A basal cell carcinoma is a type of basal cell tumor that is malignant or cancerous. Fortunately, less than 10% of basal cell tumors are malignant.

"Fortunately, less than 10% of basal cell tumors are malignant."

What causes basal cell tumors?

The reason why a particular pet may develop a basal cell tumor, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary. Certain breeds of dogs are more likely to develop basal cell tumors, including Kerry Blue and Wheaten Terriers, Cocker Spaniels, Poodles, Shelties, and Siberian Huskies. Siamese, Persian, and Himalayan cats are most often affected.

What are the clinical signs of basal cell tumors?

Basal cell tumors vary in size, from a few centimeters to inches in diameter, and most commonly appear as single, firm, hairless, raised masses in the skin, often on the head, neck, or shoulders. Occasionally, they may be cystic or ulcerate, and some may stick out like stalks from the skin surface. The tumors are sometimes pigmented, especially in cats.

How are basal cell tumors diagnosed?

Typically, these tumors can be diagnosed by fine-needle aspiration (FNA). FNA involves using a small needle with a syringe to suction a sample of cells that a veterinary pathologist will examine under a microscope. In some cases, results from FNA may not be entirely clear and biopsy (surgical removal of a tissue sample) may be necessary. Examination of this sample is called histopathology. Histopathology is helpful to make a diagnosis and can also indicate how the tumor is likely to behave.

How do basal cell tumors typically progress?

Although these types of tumors are most often benign and will not spread (metastasize) to the surrounding tissues or internal organs, they may continue to grow, with greater chances of ulceration, infection, and difficulties with removal. Metastasis, though rare, is more common in cats than in dogs. If the tumor is removed, the prognosis is excellent.

"If the tumor is removed, the prognosis is excellent."

What are the treatments for this type of tumor?

Surgery is the treatment of choice for basal cell tumors and basal cell carcinomas. Surgery reduces the risk of secondary infection and inflammation as well, especially with tumors that are cystic or ulcerate. There are some reports of tumors recurring at surgical sites, but this is rare. Cryosurgery, a technique that uses a liquid nitrogen spray to freeze the tumor, may be an option for treating smaller tumors.

Is there anything else I should know?

Your pet should not be allowed to bite, lick, or scratch the tumor, as this may cause it to ulcerate and bleed. As secondary infection is possible, your veterinarian may prescribe antibiotics if necessary.

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