Hair Follicle Tumors in Cats

Although hair follicle tumors are often benign, they are similar in appearance to other types of tumors that are potentially malignant and dangerous. Any time a cat presents with an unexplained mass, a trip to the vet is warranted. Early detection and treatment is often critical to increasing the chances of recovery.

Hair follicle tumors often begin as small cysts (1 to 5 centimeters) in the middle or lower layers of the skin. If the cyst grows or the cat scratches or bumps the area, skin ulcers may develop. The tumors are generally round and firm, and there is typically only a singular tumor in the affected area, although multiple tumors are possible. The condition is fairly rare in cats, and the tumors are usually slow-growing, non-invasive, and unlikely to metastasize.

Hair follicle tumors usually do not cause symptoms other than lumps below the surface of the skin. If the tumor ulcerates, it may ooze a blood-tinged fluid and infection is possible.

If the tumor is malignant, it may cause one or more of the following symptoms:

• Extensive inflammation
• Tissue death
• Fibrosis

Types

There are two primary types of hair follicle tumors that are found in cats. Trichoepitheliomas are small and usually benign. These tumors are often found on the shoulders, back, limbs, flank, or tail. Pilomatricomas, a rare type of tumor, generates directly from the hair-follicle producing cells. This is usually found on the cat’s trunk or torso. 

No definitive cause has been found, but there is speculation that hair follicle tumors could be linked to a genetic predisposition. There has been some evidence that it may be more prominent in the Siamese breed.

The veterinarian will review the cat’s full medical history and discuss its overall health and details regarding the onset of symptoms. A physical exam will be performed and a standard set of laboratory tests will be ordered including complete blood count (CBC), electrolyte panel, and urinalysis.

Skin follicle tumors are often hairless and are similar in appearance to basal cell carcinoma, so a differential diagnosis is often needed. The vet will typically remove a sample of the tumor using a fine needle aspiration, which pulls a fluid from the tumor, or a biopsy which extracts a piece of the tissue. Biopsies often require anesthesia, while aspirations may be less invasive. The sample will be sent to a lab for analysis to determine the specific type of tumor and whether it is malignant or benign.

The recommended course of treatment will depend on the size, type, and location of the tumor, and whether it is malignant or benign.

Surgical Removal

In most cases, removal of the tumor is recommended. This is often the most effective and least expensive treatment option. Generally, a portion of the surrounding healthy tissue will also be removed in order to ensure that the entire tumor has been extracted. Since most hair follicle tumors are benign, prognosis following treatment is generally excellent and the condition is considered completely cured once the tumor has been successfully removed.

Laser and Cryotherapy

Small tumors located near the surface of the skin may be removed non-surgically using lasers or cryotherapy (freezing).

Treatment of Malignant Tumors

If the lab tests determine that the tumor is malignant, a consultation with a veterinary oncologist may be needed. In this case, it is possible that the cancer may spread to other areas of the body. If the tumor cannot be completely removed, partial removal may still increase survival chances. Radiation treatment or chemotherapy may also be recommended to reduce tumor size and increase the chances of survival. Unfortunately, malignant hair follicle tumors often metastasize very rapidly and may have spread significantly before the primary tumor has been noticed. In this case, prognosis is guarded at best. 

Following surgery, antibiotics will be prescribed and the cat may need to be placed in an Elizabethan collar to prevent licking of the surgical area. High doses of omega-3 fatty acids may be recommended to aid in healing.

Once a cat has been treated for hair follicle tumors, it will need to be continually monitored. It is likely that additional tumors will develop on other areas of the body. Owners should frequently check the cat for any new lumps. If new symptoms are noticed, the vet should be notified immediately. It is important not to assume that subsequent tumors will be the same type. Each mass should be examined separately to determine whether it is benign or malignant. The vet will recommend the proper course of treatment for each separate incidence.