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Sweat Gland, Hair Follicle, and Sebaceous Gland Tumors

By Christopher Pinard, DVM

Tumors, Pet Services

What are sweat gland, hair follicle, and sebaceous gland tumors?

skin_layers_sweatglandshairsebaceousglands_2018These tumors develop from disordered growth of cells related to either the sweat glands (which dogs and cats still have, even though they do not sweat the same way people do), hair follicles, and sebaceous glands (the glands that produce the oils of the skin).

Some pets will develop one or more of these kinds of tumor in more than one location. These tumors are mostly benign, but some (e.g., matrical carcinoma and sebaceous gland adenocarcinoma) are not. These malignant tumors, however, are very rare.

What causes these tumors to develop?

The reasons why a particular pet may develop these or any other kinds of tumors is not straightforward. Very few 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. In the case of sweat gland, hair follicle, or sebaceous gland tumors, there is no known cause.

What are the signs that my pet has one of these types of tumors?

The most notable thing you will observe is solid, firm or raised areas (lesions) on the skin. These masses may be haired or ulcerate (break open) and bleed, and are well-defined (meaning you can feel the edges of the mass).

Occasionally these masses develop in undesirable locations that can become irritated, ulcerated, or infected. This may cause your pet to chew or lick the area which can cause further damage to the surrounding skin.

"Occasionally these masses develop in undesirable locations that can become irritated, ulcerated, or infected."

If a mass grows near, or on the edge of, the eyelid, it can irritate the eye or cause corneal ulcers (scratches on the clear surface of the eye). In this case, you may see your pet squinting or scratching at their face excessively.

How are these tumors diagnosed?

These masses are usually diagnosed either by fine needle aspiration (FNA) or by surgical removal. FNA involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide. A veterinary pathologist then examines the slide under a microscope. Because it is very common for these tumors to contain secretions (the liquid produced by the glands) these samples are not always useful for diagnosis.

These tumors are sometimes surgically biopsied or completely removed. A biopsy is a surgical excision of a piece of the tumor. Pieces of the tumor are then examined by a veterinary pathologist under the microscope. This is called histopathology. Histopathology is not only helpful to make a diagnosis but can indicate how the tumor is likely to behave.

How do these types of tumors typically progress?

These tumors typically progress by growing in the same location that they developed. They do not tend to spread to other areas of the body. Their growth can be slow or fast, depending on the type of tumor and the pet.

What is the treatment for these types of tumors?

If these masses grow, become bothersome, or are of any concern, the best treatment is to surgically remove them. Given that they are typically benign, the surgical procedure tends to be straightforward. Once the mass is removed, it is sent to a pathologist to confirm that it is benign.

"Given that they are typically benign, surgical removal tends to be straightforward."

In cases of the malignant forms (matrical carcinomas or sebaceous gland adenocarcinomas) your veterinarian may recommend one or more of surgery, chemotherapy, and radiation.

Is there anything else I should know?

In most cases, these masses are not bothersome. After fine needle aspiration or surgical procedure, the area may be irritated. Pain medications – and an Elizabethan collar (E-collar or cone) to prevent licking – can help to reduce pain and inflammation after biopsy or surgery. Your pet should not be allowed to bite, lick, or scratch the area.

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