Animal Reference Pathology

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Perianal Gland Adenoma

General Information

            The perianal glands are modified sebaceous gland and are also sometimes referred to as hepatoid glands or circumanal glands. Thus, other names for perianal gland adenomas are hepatoid gland adenoma and circumanal gland adenoma. The function of perianal glands is not fully understood, but it is thought that their secretions play a role in steroid metabolism, production of pheromones, and territorial marking. They are only found in canines (dogs, wolves, and their relatives). These glands are located in the skin around the flank, groin, anus, and the top and bottom of the tailhead, but can be found anywhere in the skin. The perianal glands are usually much larger and more extensive in adult males.

            Perianal gland adenomas are benign tumors. The most common locations for perianal gland adenomas are around the perineum, the groin, and the top and/or bottom of the tailhead. Dogs may have a single or multiple perianal gland adenomas and individual tumors can vary in size. Perianal gland adenomas are usually very slow growing, non-painful and dogs usually don’t show any symptoms associated with the tumor. Occasionally, some tumors may become inflamed and infected which can cause pruritus, irritation and mild pain.  If tumors around the perineum are large enough, they can interfere with defecation.

            The cause of perianal gland adenomas is unknown, but androgen production may stimulate tumor formation. Estrogen has suppressive effects on perianal gland adenoma formation.

Factors that Increase the Risk of Developing Perianal Gland Adenoma

  • Older intact males
  • Age: 8 years and older
  • Breeds at an increased risk of developing this type of tumor: Siberian Huskies, Samoyeds, Pekinese’s, Cock-a-poos, Cocker Spaniels, Brittany Spaniels, Lhasa Apso's, Shih Tzu’s, mixed breeds, and Beagles

            Breeds that are at a decrease risk of developing perianal gland adenomas are German Shepherds, English Springer Spaniels, Standard Poodles, Labrador Retrievers, Miniature Schnauzers, Great Danes, Golden Retrievers, Doberman Pinschers, Boxers, and Rottweiler’s.

            Females that have not been spayed are also at a decreased risk because of estrogen’s suppressive effects on tumor development.

Treatment

            For intact male dogs that have a perianal gland adenoma, surgical removal of the tumor and castration are the best treatment options. In males that have large tumors, castration prior to tumor removal may help decrease the size of the tumor and facilitate complete excision.

            For females, surgical removal is the treatment of choice.

It is always easier to remove smaller tumors than larger tumors, so surgery is generally recommended before the tumor reaches a size that can make excision more challenging, particularly when the tumor is located in regions that make closing the surgical wound problematic.

Prognosis

            With complete excision the prognosis is excellent. Return of the tumor is very rare after complete excision. Incompletely excised tumors can come back.  The completeness of excision requires microscopic examination by a veterinary pathologist

Some dogs can develop de novo perianal gland adenomas from the remaining non-neoplastic perianal glands that were not removed.

Comparative Aspects

            Since the perianal glands are unique to the canine species, perianal gland adenoma is not seen commonly in other species, including humans.          

References

Kennedy, Peter and Nigel Palmer. "Tumors Arising from Sebaceous or Modified Sebaceous Glands." Pathology of Domestic Animals. By Kenneth Jubb. 5th ed. Vol. 1. St. Louis: Elsevier Mosby, 2007. 756-57. Print.

McGavin, M. Donald., and James F. Zachary. "The Integument." Pathologic Basis of Veterinary Disease. 4th ed. St.Louis: Elsevier Mosby, 2007. 1115. Print.

Withrow, Stephen J., David M. Vail, E. Gregory. MacEwan, and Rodney L. Page. "Perianal Tumors." Withrow & MacEwen's Small Animal Clinical Oncology: Stephen J. Withrow, David M. Vail, Rodney L. Page. 5th ed. St. Louis, MO: Saunders Elsevier, 2013. 423-31. Print.