Are you a dog lover worried about your furry friend’s health? Hepatoid gland tumors may be a cause for concern. In this article, we will delve into the world of hepatoid gland tumors – a type of skin cancer that affects dogs. Read on to learn more and discover how to identify and manage these tumors effectively.
What are hepatoid gland tumors?
Hepatoid gland tumors are a specific type of cancer that originates from hepatoid glands, which are modified sebaceous (sweat) glands found in the skin of dogs. These glands are primarily located in the perianal area, including the region around the anus, as well as the prepuce, base of the tail, groin, inner thigh, and back. The tumor cells in hepatoid gland tumors bear a striking resemblance to liver cells.
Approximately 10% of all diagnosed skin cancer cases in dogs are hepatoid gland tumors. The perianal area is the most common location for these tumors. Within the perianal area, three primary types of tumors can occur: adenomas (benign), adenocarcinomas (malignant), and epitheliomas (borderline malignant). Perianal adenomas, accounting for 80% of perianal tumors, are more prevalent in intact (unneutered) male dogs and rank as the third most common tumor type in unneutered males. Adenocarcinomas are uncommon, while epitheliomas are rare.
What causes this cancer?
The development of hepatoid gland tumors in dogs is not attributed to a single cause. Rather, it is influenced by a complex interplay of various risk factors, including genetic and hereditary factors as well as environmental influences. Hormones, particularly testosterone and estrogen, play a significant role in tumor development and growth. Testosterone promotes the onset of these tumors, making perianal adenomas and adenocarcinomas more common in unneutered male dogs. Conversely, estrogen inhibits their development, resulting in a higher incidence in spayed female dogs. These tumors are also associated with other forms of cancer, such as testicular and adrenal gland tumors, as well as Cushing’s Disease (hyperadrenocorticism).
Additionally, certain breeds are more susceptible to hepatoid gland tumors. Siberian Huskies, Cocker Spaniels, Pekingese, and Samoyeds are more prone to perianal adenomas, while Siberian Huskies, Bulldogs, and Alaskan Malamutes have a higher incidence of perianal adenocarcinomas.
What are the signs of these tumors?
The manifestation of hepatoid gland tumors can vary depending on whether they are benign or malignant. In the case of benign perianal adenomas, you may notice small, round, pink, hairless nodules appearing around the anus. Although these growths primarily occur around the anus, they can also develop in the prepuce, scrotum, and under the tail. Occasionally, they may ulcerate and become infected, leading to irritation and discomfort, prompting your dog to frequently lick the affected area.
Adenomas and adenocarcinomas bear a resemblance, but adenocarcinomas tend to grow more rapidly and can reach sizes of up to 4 inches (10 cm) in diameter. Furthermore, adenocarcinomas are more likely to occur as multiple tumors. Due to their potential to spread to the lymph nodes and underlying tissues, they can exert pressure on the rectum, causing difficulty in defecating (straining) and constipation.
Moreover, adenocarcinomas can induce a condition called paraneoplastic hypercalcemia, characterized by elevated blood calcium levels. This condition occurs in approximately 30-50% of dogs with adenocarcinoma. Hypercalcemia may present as increased drinking and urination, loss of appetite, weight loss, lethargy, weakness, vomiting, and constipation.
How are these tumors diagnosed?
A veterinarian can suspect hepatoid gland tumors based on their characteristic appearance or by detecting a mass or enlarged lymph nodes during a rectal palpation. Remarkably, 35-40% of perianal adenocarcinomas are discovered incidentally during rectal palpation, showing no external signs of disease.
To diagnose a suspected tumor, a microscopic examination of the tissue is required. Veterinarians may employ various methods to obtain a tissue sample for diagnosis. The most common approaches include fine needle aspiration (FNA), biopsy, or complete excision of the tumor.
Fine needle aspiration involves using a small needle and syringe to extract a sample of cells directly from the tumor, which are then placed on a microscope slide for examination by a veterinary pathologist. In some cases, FNA results may not provide a definitive diagnosis, necessitating a biopsy. Biopsies involve surgically removing one or more pieces of the tumor, which are subsequently examined under a microscope by a veterinary pathologist in a process called histopathology. Histopathology not only aids in making a diagnosis but also provides insights into the tumor’s behavior. Alternatively, the entire tumor may be excised and sent for histopathology.
How does this cancer typically progress?
Perianal adenomas tend to grow slowly and reach a limited size, typically less than 1 inch (3 cm) in diameter. Epitheliomas behave similarly to adenomas, but they can infiltrate the surrounding tissues. Both adenomas and epitheliomas are prone to ulceration and infection.
On the other hand, perianal adenocarcinomas exhibit rapid growth, infiltrate underlying tissues, and can metastasize to the local lymph nodes, abdominal organs, and lungs. Tissue invasion and lymph node involvement can cause difficulties in defecation. Metastasis to other organs may result in organ damage, systemic illness, lethargy, and weight loss. To assess potential spread to other parts of the body, staging is highly recommended for adenocarcinomas. Staging procedures may include bloodwork, urinalysis, radiographs (X-rays) of the lungs, and possibly an abdominal ultrasound. If any lymph nodes appear enlarged or abnormal upon examination, further sampling may be pursued to ascertain the presence of metastasis.
What are the treatments for these tumors?
The choice of treatment for hepatoid gland tumors depends on various factors, including the tumor type, size, malignancy, and presence of metastasis. Treatment options typically include surgical removal of the tumor, neutering in male dogs, cryotherapy, laser ablation, radiotherapy, chemotherapy, and occasionally hormone therapy.
For most perianal adenomas in intact male dogs, the treatment of choice involves castration and tumor removal. Often, small tumors regress or do not progress after neutering and may not require surgical intervention if they are not ulcerated. In cases where the tumors are large, multiple, or located in proximity to the anal sphincter, neutering is advised first, followed by a waiting period of several months before tumor removal. Without the influence of testosterone from the testes, the tumors will shrink, making their removal safer and easier. Surgical removal is indicated for adenomas in female and neutered male dogs.
When adenomas measure less than 1 to 2 cm in diameter, cryotherapy or laser ablation may be employed as alternatives to surgical removal. If adenomas recur after neutering and initial tumor removal, a second biopsy is strongly recommended to exclude adenocarcinoma, along with testing for underlying hyperadrenocorticism.
For perianal adenocarcinomas, complete surgical excision of the tumor, sometimes with removal of nearby lymph nodes, and neutering constitute the preferred treatment. Radiation or chemotherapy may also be recommended for these tumors. Successful therapy will result in a return to normal blood calcium levels in cases of paraneoplastic hypercalcemia.
Is there anything else I should know?
The prognosis for perianal adenomas is generally favorable with neutering and tumor removal, with recurrence rates below 10%. Failure to neuter often leads to the reoccurrence of adenomas and the development of new tumors. Epitheliomas generally carry a good prognosis, although occasional regrowth may occur.
The prognosis for perianal adenocarcinomas is fair to guarded due to the potential for tumor regrowth, tissue invasion, and metastasis. For dogs initially presenting with hypercalcemia, vigilant monitoring of blood calcium levels is necessary as increases may indicate tumor recurrence or metastasis. Your veterinarian and veterinary oncologist will provide guidance on the most suitable treatment options to achieve the best possible outcomes.
In conclusion, hepatoid gland tumors in dogs require timely and appropriate management. By familiarizing yourself with the signs, causes, and treatment options, you can become an informed and proactive advocate for your beloved canine companion. Stay informed and always consult with your veterinarian for personalized advice and guidance on managing hepatoid gland tumors to ensure the wellbeing of your furry friend.
