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Perianal Tumors In Dogs

Perianal Tumors In Dogs

What Is Perianal Tumors In Dogs?

Tumors in the perianal and perineal regions are common in dogs. The perianal region consists of the area immediately around the anus (posterior or lateral to the anus) whereas the perineal region is clinically defined as the region of the perineum (between the anus and the Labia Magna or scrotum).

Perianal Tumors are the ones that develop on or close to the anus. Tumors that frequently develop in this area include perianal adenocarcinoma, perianal adenoma (Also called hepatoid tumors, circumanal tumors), and anal sac adenocarcinoma (Anal gland adenocarcinoma). Other rare cutaneous and subcutaneous tumor types such as squamous cell carcinomas, soft tissue sarcoma, and mast cell tumors may occur in this location.

Greater than 80% of perianal tumors are benign perianal adenoma in non-neutered male dogs. These are typically slow-growing, androgen-dependent, non-painful masses that occur in the sebaceous glands (sweat glands) in the perianal region. They can be single, multiple, or diffused and if the dog traumatizes the mass, they can become infected or ulcerated.

The malignant counterpart of perineal adenomas is perianal adenocarcinomas. clinically similar but adenocarcinoma, these tumors tend to be more invasive, faster-growing, relapse following excision, and occur in intact males, or females and castrated males.

Anal gland adenocarcinoma (AGA) is reported to represent 17% of perianal tumors in dogs and usually tends to occur in middle-aged to older dogs.

AGA has no breed disposition and occurs in both males as well as females. This uncommon cancer tends to be locally invasive in the surrounding tissues and has a high rate of metastasis (spread to distant tissues).

Symptoms Of Perianal Tumors In Dogs

General Symptoms of tumors in the perianal region may include:

  • Scooting
  • Constipation, Obstipation, Dyschezia, Tenesmus
  • Excessive licking of the perianal area.
  • Narrow or ribbon-like stools or blood in stools.
  • Inflammation of external swelling in the perianal region.
  • Polyuria, Polydipsia

Dog owners may also observe symptoms of kidney failure from the elevated calcium (paraneoplastic syndrome).

These symptoms generally include:

  • Increased thirst and urination may occur.
  • Vomiting
  • Lethargy
  • Anorexia
  • Muscle Weakness

Treatment Options For Perianal Tumors In Dogs

Usually, many tests are suggested to detect the tumor, evaluate for metastasis and present a clear clinical picture of overall health:

  • For dogs with small (diameter less than 3cm): primary tumors and if the tumor hasn’t spread, the most appropriate therapy is local surgical excision. Post-operatively to improve the tumor control, radiotherapy may be used.
  • Dogs with primary tumors (greater than 3cm), no evidence of metastasis: chemotherapy (e.g. mitoxantrone or carboplatin) can be used to attempt to shrink the tumor. More recently, melphalan is tested to be an efficient chemotherapy agent and Palladia (tyrosine kinase inhibitors ) was found to be beneficial.
  • Again, radiotherapy may be used post-op to reduce the duration of the resulting remission.
  • Due to the fact that locally invasive nature and a high rate of local metastasis of AGA, If the spread has happened to distant sites such as the liver or lungs, surgery or radiation as a definitive treatment is generally not recommended.
  • In dogs with distant spread, treatment is aimed at palliation (hypofractionated radiation therapy) to provide dogs more comfortable by relieving clinical signs).
  • Hypofractionated megavoltage radiation therapy provides partial regression or stabilization of tumor size with alleviation of clinical signs in 75% of affected dogs.

Home Remedies For Perianal Tumors In Dogs

  • After surgery, Dog activities should be restricted activity for about 2 weeks to allow recovery and incision healing.
  • A restrictive collar usage is recommended for 10-14 days. This prevents the natural tendency of dogs to lick and chew at a wound.
  • A diet of roughly 50% meat and 40–50% whole grains or non-starchy vegetables is optimal.
  • A home-prepared diet with Dark leafy greens.
  • Fish oils or fish meals, or whole fish are rich in omega-3 fatty acids.

Prevention Of Perianal Tumors In Dogs

Pet owners may not notice the few clinical signs and the condition in its early stages of development.

As the disease progresses, if your dog’s anal area becomes inflamed, has an open sore or you see pus around its anus, you should contact the vet.

The affected dog will usually lick excessively at its tail and rectal regions; there will be blood in the feces and strain during defecation.

Affected Dog Breeds Of Perianal Tumors

Siberian Husky, Beagle, Cocker Spaniel, Cavalier King Charles Spaniel, English Bulldog, Samoyed, Senior Dogs, Fox Terrier

Additional Facts For Perianal Tumors In Dogs

  1. Causes:
  • Hereditary Reasons
  • Excessive Testosterone Production
  • Hyperadrenocorticism
  • Testosterone-producing Adrenal Tumors
  • Testicular Tumors
  1. Types:

Benign Adenomas:

  • While most perianal bumps are benign, meaning the bumps are non-cancerous, there are some perianal bumps that are cancerous (perianal adenocarcinomas).
  • Non-cancerous (benign) tumors pose the greatest risk to non-neutered male dogs.

Malignant Carcinomas:

  • Perianal Adenocarcinomas usually occur in intact males, or females and castrated males.
  • Anal Sac Adenocarcinoma is a rare type of cancer of the apocrine glands located in the walls of the anal sacs. These sacs can be found by the anus, more or less at 4 o’clock and 8 o’clock (imagine the back end of the dog as a clock face).
  1. Morbidity:
  • Anal gland tumors occur in male and female dogs with roughly an equal incidence.
  • They occur in any breed but are more common in Spaniel breeds.
  • The average age of affected dogs is 10 years. Older dogs are most affected.
  • With anal sac adenocarcinoma, the average survival time is approximately 12-18 months for dogs. The survival time is typically shorter if there is a metastatic disease or elevated blood calcium without surgery.
  • In most dogs, Anal sacs are the only site where this type of cancer is found, but in some cases, they may spread to the lymph nodes or via the bloodstream to places like the spleen, liver, and lungs.
  1. Mortality:

Sadly less than 50% of dogs live more than 10 - 12 months from the time of diagnosis of malignant perianal tumors. For non-cancerous tumors (such as Perianal Adenomas), the survival time is not typically associated with the presence or absence of the tumors.

  1. Diagnosis:
  • Complete blood count (CBC), serum chemistry panel (including calcium levels).
  • Fine-needle aspirate or by a surgical biopsy.
  • Abdominal radiographs, ultrasound, or CT scan.
  1. Prognosis:

For benign cases, castration and tumor removal offer a good prognosis and complete regression in the majority of these cases. Almost 75% of the dogs with perianal adenoma experience improvement in their clinical signs, ~ 30% had disease stabilization, 50% experienced a reduction in the size of the tumor and tumors recur in less than 10% of cases.

Malignant perianal tumor in dogs offers a poor prognosis. Frequent veterinary visits for treatments are required.

When To See A Vet For Perianal Tumors In Dogs?

Contact your vet right away, if you notice any of the following:

  • Scooting
  • Excessive licking of the perianal area.
  • Narrow or ribbon-like Stools or blood in stools.

Food Suggestions For Perianal Tumors In Dogs

High Protein, Good Fats and Low Carbs, antioxidants, and cancer-fighting nutrients.

Dogs: 50% veggies (dark leafy greens, carrots, broccoli, green beans, etc are good choices) + 50% protein (chicken or beef is best).

To the dog’s diet, add fiber via fiber supplements.

Unprocessed wheat bran (depending on the size of your dog - 1 to 5 tablespoons per day).

Plain canned pumpkin (5 teaspoons to ½ cup) or psyllium (Metamucil -5 teaspoons/day).

Add Grains:Barley and Oatmeals.

Add prebiotics/probiotics to your dog’s diet.

Add digestive enzymes to your dog’s diet (from herbs, seeds, and spices).


Regardless of the severity of a diagnosis of malignant cancer, most dogs can enjoy an excellent quality of life with appropriate therapy.

The most favorable prognosis can be expected with early detection and appropriate treatment. This emphasizes the significance of a rectal examination as part of a routine physical examination in all dogs.

For benign perianal tumors, recovery is very good. Complete regression of benign tumors is possible by neutering. Proper post-operative care should be provided for 3 months to monitor tumor regression.

Malignant perianal tumor recovery is poor. Many dogs can die within a year from diagnosis, or sometimes be euthanized.

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