What is Anal Gland Cancer in Dogs?
When Charlie, a five-year-old Golden Retriever, started experiencing some discomfort around his hindquarters, his owner, Lisa, became increasingly concerned. After a trip to the vet and a series of tests, the diagnosis was both unexpected and devastating: anal gland cancer. As Lisa embarked on a journey to help Charlie fight this rare form of cancer, she realized how little information was available on the subject.
Anal gland cancer in dogs is rare affecting dogs’ anal glands. The anal glands produce a lubricating fluid that helps keep the anus clean and moist. When these glands become inflamed or infected, they secrete pus instead of liquid. This causes painful swelling and irritation of the area.
Most anal gland cancers form masses, called polyps, that can be felt during rectal exams. These polyps usually do not cause symptoms, but some people notice blood in their stools. It must be removed immediately if you find a mass in your dog’s anus. This cancer rarely affects older dogs, but younger ones may develop it.
Anal gland cancer is one of the most commonly diagnosed cancers in dogs. It accounts for about 2% of all canine tumors. This type of tumor usually affects older dogs, especially those over ten. There are three types of anal gland cancer: squamous cell carcinoma, adenocarcinoma, and transitional cell carcinoma. Squamous cell carcinomas account for 70% of cases, while adenocarcinomas make up 20%. Transitional cell carcinomas are rarer.
- Squamous Cell Carcinoma
Most SCCs occur spontaneously, meaning they aren’t caused by external factors such as chemicals, radiation, or viruses. However, some SCCs are associated with certain diseases or conditions, including diabetes mellitus, hyperthyroidism, chronic kidney disease, immune suppression, and genetic disorders.
Anal sac adenocarcinomas are rare in dogs. They occur most often in middle-aged male dogs. They are less common in female dogs and very uncommon in puppies. Treatment includes surgical removal of the tumor and radiation therapy.
- Transitional Cell Carcinoma
This type of cancer occurs when cells change into another kind of cell. It’s also known as urothelial carcinoma because it develops in the bladder, urethra, or both. Urothelial carcinomas are more likely to affect males than females.
Causes of Anal Gland Cancer in Dogs
The most common cause of anal gland cancer in dogs is chronic irritation due to parasites. Other causes include anal sacculitis (an infection), genetic predisposition, trauma, hormonal imbalance, and neoplasia (cancer).
- Chronic Irritation
Chronic irritation from parasites causes anal gland cancer in dogs. The most common parasite causing this problem is roundworms. Roundworm eggs hatch inside the dog’s intestines and release larvae that burrow through the intestinal wall and enter the bloodstream.
These larvae travel to the liver, where they mature into adult worms. Adult roundworms live in the dog’s intestine and produce eggs that pass out of the body in feces.
Roundworms irritate the lining of the small intestine and colon. This inflammation leads to ulcers, bleeding, and, eventually, tumors.
- Genetic Predisposition
Some breeders say that some dogs are predisposed to developing the disease. This includes certain dog breeds such as German Shepherds, Golden Retrievers, Labrador Retrievers, Boxer Dogs, Poodles, Doberman Pinschers, and Bull Terriers.
An equal number of men and women are affected by anal gland cancer. However, research suggests that female dogs are less likely to develop the disease.
- Anal Sacculitis
Anal sacculitis is inflammation of the anal sacs (saclike structures) located at the base of each dog’s tail. The condition usually occurs when bacteria enter the anus and infect the glands.
When dogs lick themselves excessively, they may ingest fecal matter containing harmful bacteria, viruses, and parasites. This causes diarrhea, vomiting, fever, lethargy, loss of appetite, weight loss, and sometimes death.
Trauma causes inflammation and irritation of the anal glands, leading to cell growth and cancer. Trauma includes dog bites, fights, car accidents, and being hit by a moving vehicle.
- Hormonal Imbalance
Anal gland cancer in dogs is often associated with hormonal imbalance. Hormones play a significant role in regulating our body functions. They control growth, development, metabolism, reproduction, sexual function, moods, sleep patterns, and many other bodily processes.
When hormones become imbalanced, they may cause problems in various body parts. This includes glands, organs, tissues, and systems. For example, the most common hormone imbalance in dogs is called hyperadrenocorticism (also known as Cushing’s disease). Hyperadrenocorticism causes excessive amounts of cortisol to be produced by the adrenal glands. Cortisol is a steroid hormone that helps regulate blood pressure, immune system response, stress responses, and metabolism.
Neoplasia means cancerous growth. Neoplasms are tumors that grow out of control and spread through the body. They’re usually benign (noncancerous) but sometimes malignant (cancerous).
Anal gland neoplasia is a type of anal gland tumor that occurs when cells in the glands become abnormal. The most common types of anal gland neoplasia include squamous cell carcinoma and adenocarcinoma. Squamous cell carcinomas tend to be more aggressive than adenocarcinomas.
Symptoms of Anal Sac Cancer in Dogs
A lump near the anus is usually associated with cancer. However, it could also be caused by something else, such as hemorrhoids, parasites, or even anal glands. If you notice blood in the stool, there are several possible causes. Kidney disease, liver disease, and intestinal blockage are the most common reasons for bloody stools. Other conditions include ulcers, colitis, and pancreatic disease.
Here are some symptoms of anal gland cancer in dogs. These include:
- Abdominal pain
- Rectal bleeding
- Urination problems
If any of these symptoms occur, contact your veterinarian right away.
Diagnosis of Anal Gland Tumors in Dogs
Anal gland cancer is one of the most common cancers affecting male dogs. It accounts for about 10% of all canine tumors. This type of cancer usually affects older males, although younger dogs are sometimes affected. Most cases occur in intact males, but castrated males can develop anal gland cancer too.
Vets usually perform a rectal examination to check for lumps or masses in the area around the anus. Sometimes an ultrasound exam will be done to look at the lymph nodes in the abdomen and pelvis. In addition, blood tests may be performed to determine if there is anemia (low red blood cell count), hypoproteinemia (low protein levels), or high alkaline phosphatase (ALP) levels.
- Fine needle aspiration is the most commonly used diagnostic test for anal gland cancer. This involves taking a small sample of cells from the tumor under local anesthesia. If the cells look abnormal, a biopsy with histopathology examination is needed to confirm whether the cells are malignant.
- A biopsy with histopathologic examination is needed to confirm anal gland cancer. In addition, your veterinarian needs to know if any other medical conditions are causing the symptoms before diagnostics anal gland cancer.
- Chest radiographs can detect lung metastasis, but abdominal ultrasound can show if the tumor has spread to internal organs such as the liver, kidney, bladder, etc.
Treatment Options for Anal Sac Tumors in Dogs
There are several types of anal gland cancers. Most occur in the anal sacs, tiny structures containing lymph nodes. These tumors are called anal sac adenocarcinomas. Other forms of anal gland cancer include squamous cell carcinoma and transitional cell carcinoma. Treatment of anal gland tumors depends on the stage of cancer.
Surgical removal of the anal gland is usually performed if the dog is diagnosed early enough. A biopsy is used to determine whether the tumor is malignant. If the tumor appears benign, no treatment is needed. However, chemotherapy and radiation therapy may be recommended if the tumor is malignant.
Prednisone is administered before surgery to reduce inflammation and help prepare the body for the procedure. Afterward, the dog receives antibiotics to prevent infection.
- Radiation Therapy
Another option is radiation therapy. Radiation therapy uses X-rays to kill cells actively dividing (growing). This helps prevent the spread of cancer.
Radiation therapy is often combined with chemotherapy. Chemotherapy drugs work by killing rapidly growing cells. They’re typically given after surgery or radiation therapy.
Radiation therapy is still recommended if the tumor is not removed during surgery. However, radiation therapy does not cure anal gland cancer in dogs but can help control the disease.
Other options include cryosurgery, where liquid nitrogen freezes the tumor, and immunotherapy, where antibodies are injected directly into the tumor.
Cryosurgery is usually only used when the tumor cannot be completely removed surgically. Immunotherapy is rarely used because it requires multiple injections over a long period.
When deciding between surgery and radiation therapy, consider the following factors:
- Location of the tumor – Is the tumor close to the anus or rectum?
- Size of the tumor – Does the tumor grow slowly or quickly?
- Age of dog – Is the dog’s immune system strong enough to fight off cancer?
- The dog’s overall health – Is the dog overweight or underweight?
Recovery and Management of Anal Gland Cancer in Dogs
The anal glands are located inside the anus and produce a fluid called anal mucus. They secrete this liquid into the rectum, where it helps keep fecal matter soft and moist. When anal gland cancer occurs, the cells lining the glands become abnormal and produce too much mucus. This causes the feces to harden and dry out. As the disease progresses, the anal glands enlarge and eventually rupture. Left untreated can lead to painful bowel movements and even death.
Treatment options depend on the stage of cancer. Surgery is often used to treat the early stages of anal gland cancer. Radiation therapy is another option for treating early-stage tumors. Chemotherapy drugs such as doxorubicin and cisplatin are sometimes administered to patients with late-stage anal gland cancer.
A biannual visit schedule for dogs who had anal gland cancer surgery is recommended. During the initial recovery period, owners must watch for signs of infection. Infections can occur because the surgical site becomes inflamed and swollen. Therefore, owners should monitor their pets closely during this time. Once the swelling subsides, the wound should heal without complications.
Fecal incontinence can develop following anal gland cancer surgery. This is caused by damage to nerves that control the muscles responsible for controlling defecation. The problem typically resolves within six months, although some dogs experience symptoms for more extended periods.
Frequently Asked Questions
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