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Medical Oncology: Canine Apocrine Gland Anal Sac Adenocarcinoma (AGASACA)

What Is An Anal Gland Tumor?

Apocrine gland anal sac adenocarcinomas (AGASACA) are tumors of the anal glands. These are paired glands located on either side of the rectum. Anal glands are sweat glands that contain a brown, foul-smelling liquid eliminated upon defecation.

AGASACAs are locally invasive tumors with a high rate of metastasis (spread) to lymph nodes.

Tumors can also spread to internal organs including the liver, spleen, and lungs. Metastasis is possible even in cases where the anal gland tumor is small.

These tumors can cause blood levels of calcium to rise above normal. Dogs with high blood calcium levels show increased thirst, urination, upset stomach signs, and lethargy. In severe cases, this causes heart and kidney damage.

Spaniels are affected more frequently than other breeds. Only one gland is usually affected, however, the disease can occur in both glands at the same time, or several years apart.

What Are The Clinical Signs?

Clinical signs include “scooting,” licking/chewing the affected area, straining to defecate and/or urinate, constipation, bloody stool, vomiting, decreased appetite, lethargy, increased thirst or urination, or swelling in the rectal region. The mass may be found on routine physical examination or by a groomer attempting to empty a pet’s anal glands.

What Diagnostics Are Performed?

If an anal gland mass is found, a fine needle aspirate is recommended. During this procedure, a small needle is inserted into the mass to obtain a sample of cells. Sedation may be necessary. Some cases require surgery for a definitive diagnosis. Blood tests (complete blood count and serum chemistry panel) are done to assess the patient’s overall health and record the serum calcium level. Further tests include abdominal ultrasound and thoracic radiographs or whole-body CT scan, and sampling of lymph nodes to evaluate for disease spread.

Treatment Options Available And Prognosis:

Surgery to remove a tumor is recommended in most cases. Complete excision can be challenging, especially when tumors are large or invasive. Surgery can include the removal of internal lymph nodes, especially in cases presenting with elevated calcium levels or signs of constipation. Referral to a boardcertified veterinary surgeon is recommended to discuss the surgery and potential complications of resection of these tumors given their location.

Radiation therapy is used for incompletely excised tumors or palliation of signs associated with nonresectable tumors and/or metastatic lymph nodes. There are several options for radiation therapy that will be discussed during your consultation.

Chemotherapy is sometimes recommended for dogs when there is a concern about the spread of disease. Options include intravenous or oral treatments. Oral steroids are sometimes used to help treat dogs with elevated blood calcium levels. Alternatively, an oral non-steroidal anti-inflammatory drug (NSAID) can help with pain and inflammation.

The prognosis for anal gland tumors is variable. It depends on the biopsy report, size of the tumor, the extent of disease, presence of hypercalcemia, ability to remove the disease with surgery, and type of treatment pursued. Some dogs can be cured with surgery alone. Dogs with more aggressive tumors that are treated with surgery, radiation therapy, and chemotherapy have an average survival of over 2.5 years. When less intensive treatment plans are pursued, the prognosis is typically shorter. Anal gland adenocarcinoma is one of the most challenging tumor types to predict survival. Dogs with widespread metastases can live many months with their disease.

Navigating Through My Options:  

TreatmentIndicationTreatment ScheduleCost*
Surgery Primary or recurrent tumors and metastatic lymph nodes Pre-surgery CT scan, preliminary
diagnostics, and followup
$4,000 - $6,000
Radiation Therapy

  • Definitive

  • Stereotactic

  • Palliative

Definitive: Incompletely excised anal gland tumors (+/- regional lymph nodes)
Stereotactic or Palliative: Non-resectable tumors and metastatic lymph nodes
CT scan, radiation treatments Definitive: $8,000-$10,000
Stereotactic: $10,000-$12,000
Some tumors after surgery
Non-resectable tumors
Metastatic tumors
IV every 1-3 weeks depending on drug and
treatment plan
$450-$600 per treatment
Tyrosine Kinase
Non-resectable tumors and metastatic lymph nodes Oral medication every other day or three times per week $300-$650 per month depending on pet size
Non-Steroidal Anti-
Inflammatory Drugs
 Relief of pain and inflammation Oral medication daily $100-$200 per month
Bisphosphonate (Zoledronate) High blood calcium levels IV injection every 4 weeks $300-$350 per treatment

* Cost estimates are based on individual appointments and the overall cost is dependent on patient response and does not include additional supportive care or hospitalization if required.

Getting started

Once you have determined the best therapeutic option for your pet, you will work with our oncology team to develop an appointment plan.

Scheduling: Patients undergoing treatments must have a scheduled appointment before arrival.

  • Schedule future appointments at reception upon checkout.
  • Drop-offs are between 7:30-8:30 am.
  • Pick-up times are arranged on the morning of the appointment: usually between 3:45-5:30.
  • No discharges are done from 2:30-3:30 pm as our oncology team is in rounds.