Hair Follicle Tumors in Dogs

Hair follicle tumors develop as a result of the disordered growth of the hair follicles. There is a genetic predisposition to developing hair follicle tumors, and they are more likely to occur in the Golden Retriever, Standard Poodle, Miniature Schnauzer, English Springer Spaniel, Irish Setter, German Shepherd, Cocker Spaniel, Norweigan Elkhound, Keeshond, Kerry Blue, Bedlington Terrier, Bichon Frise, and Basset Hound breeds.

The primary symptom of hair follicle tumors is the palpable tumor on the surface of a dog’s skin. Tumors may ulcerate and ooze bloody fluid and are at a risk of becoming infected.

Types

Infundibular Keratinizing Acanthoma tumor develops in the upper part of the hair follicle and may be solitary or multiple. These are likely found on the back of the neck and trunk. They discharge keratin and pus and/or blood. These more commonly occur in males than females, and the average age of occurrence is five years.

Trichoepithelioma tumor is typically found in middle age dogs, on the back, shoulders, trunk, tail and limbs. They ulcerate and can discharge pus and/or blood. In German Shepherds, they are likely to occur in multiple sites, although they can occur singularly.

Trichoblastoma tumors develop in hair matrical cells (cells at the root of the hair follicle), are usually solitary, and are likely found at the head, neck and base of the ear. They are most likely to occur in the Standard Poodle and Cocker Spaniel breeds.

Pilomatricoma tumors develop in hair matrical cells and are usually solitary. However, there is an extremely rare malignant form of pilomatricoma that can metastasize and spread throughout the body. However, only five cases of multiple malignant pilomatricoma have ever been recorded in the United States. Certain breeds with continuous hair growth are most susceptible to developing this type of tumor because of the constant cell division occurring in their hair follicles. These are the Kerry Blue, Poodle, Bedlington Terrier, Schnauzer, and Bichon Frise breeds.

The cause of hair follicle tumors is unknown, although there seems to be a genetic connection, as the correlation of certain physical structures of follicles of certain breeds, that may contribute to their development. Development of hair follicle tumors is also associated with excess production of the naturally occurring chemical B-catenin, which enables hair follicles to develop from skin cells.

Diagnosis depends upon a thorough reporting of the onset of your dog’s health history and the onset of symptoms, as well as a complete physical examination. This will include a chemical blood profile, a complete blood count, and a urinalysis that will include an electrolyte panel. These tests will determine the overall health of your dog and reveal any other issues.

The veterinarian will suspect a hair follicle tumor upon physical examination, and will then take samples of the tumor through biopsy or fine needle aspirate to submit to a veterinary pathologist for histopathologic laboratory analysis. The veterinary pathologist will report the results, of which the analysis will help provide transparency to the type of hair follicle tumor and if it is benign or malignant.

Treatment is surgical removal of the tumor itself, and this is a simple procedure for singular, benign hair follicle tumors.

Multiple infundibular keratinizing acanthomas will each be removed surgically, and your dog’s coat may need to be shaved completely. This will be followed by antibiotics and high doses of omega-3-fatty acids.

Trichoepithelioma may be found to be malignant; however, this type of cancer does not metastasize and is usually cured by removal of the tumor or tumors themselves.

In the unlikely event your dog is diagnosed with malignant pilomatricoma, you will be referred to a veterinarian oncologist to discuss treatment. Prognosis for this incredibly rare form of cancer is poor.

Recovery involves the proper care of the surgical site and your dog’s skin. The area must be kept clean and monitored for healing. You cannot allow your pet to rub, scratch, lick or bite the affected area; an Elizabethan Collar, which is provided to prevent your dog from licking or biting due to irritation, may be necessary. Report any negative changes to the site to the veterinarian immediately.

Most tumors are completely cured by surgical excision. Prognosis of benign hair follicle tumors is typically excellent; however, your veterinary pathologist will be able to give you an accurate prognosis based on your dog’s tumor that will include the probability of local recurrence. It is important to monitor your dog’s coat throughout its life in order to identify the recurrence of any hair follicle tumors and contact the veterinarian immediately if you identify one.