The following information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinary physician for confirmation of any diagnosis. Your pets life may depend on it.
An adenocarcinoma is a malignant tumor of any soft tissue. An anal sac adenocarcinoma is a form of cancer much more common in female dogs and is thought to be hormone related, although as yet there is no confirmed evidence available. It does not appear to be an inherited trait.
It is an extremely aggressive and invasive type of cancer in the female, particularly since it is associated with high calcium levels in the blood. Calcium hyperplasia causes such conditions as arthritis, hip dysplasia and renal failure.
Diagnosis is confirmed by a number of routine tests including blood tests and serum chemistry levels. Palpation of the area will add confirmation to the diagnosis. Chest and abdominal X-rays will need to be done to ascertain the presence of growths, and a fine needle aspiration biopsy taken to confirm the diagnosis.
The treatment of choice in suitable patients is excision followed by radiation to halt the growth and shrink the size and then chemotherapy to kill the malignant cells. Treatment is then needed to deal balance the calcium levels if present, and to treat any existing renal disease, and careful follow up over the years to deal with any subsequent growth before it becomes too large.
Treatment for the female dog is usually only palliative since the prognosis for this condition in female dogs is extremely poor. However in the case of male dogs it appears the prognosis can be good and that they will often pull through if it is caught early enough.
Anal sac adenocarcinomas are tumors arising from the apocrine glands present on either side of the rectum. They occur primarily in older (average 10 years) female dogs. Dogs might have symptoms such as straining to have bowel movements (either due to the tumor itself or due to enlarged lymph nodes in the pelvic area), or the tumors might be found incidentally on a routine physical examination. Sometimes dogs may have symptoms such as increased drinking and urinating which results from very high calcium levels in the blood (due to hormones produced by the tumor) which in turn can affect the kidneys. There is not much written about the tumors that appear in the very last inch of the GI tract in pets. Each sex has its own syndrome. Intact male dogs develop tumors of the tiny perianal glands that surround the anus. Senior female dogs develop malignancies of the anal sacs some of which manifest hypercalcemia.
The last inch of the G.I. tract in pets has the potential to develop tumors that can be fatal. If our profession continues to educate pet guardians regarding the value of neutering male dogs, many lives would be saved. Veterinarians can include rectal exams in their well dog annual physical exams. The public could also request that their pet receive a rectal exam from their vet if it is not offered initially. Awareness is the best medicine we can offer for this important last inch of the GI tract.
IN MALE DOGS:
Half of the cases initially presented to their local veterinarian with one large perianal mass which affected elimination behavior. Half of the tumors were discovered by their local vet on a routine physical exam or when the pet was presented for another reason. Some dogs presented with several nodules around the anus involving the sphincter muscles. Some of the tumors may be infected, ulcerated and cause the dog to worry the area with persistent licking and chewing the site. Generally, the dog had one or two excisional biopsy procedures prior to the metastatic event which led them to our service.
Symptoms typical of hypercalcemia are increased thirst and urine output, polydypsia and polyuria. Renal injury is a sequelae of hypercalcemia in that calcium precipitates lodge in the nephrons causing elevations of BUN and Ceatinine levels.
Affected dogs must be treated for malignant hypercalcemia with saline diuresis and monitored closely during and post surgically. Once the primary tumor is exised, the calcium level returns to normal. Recurrence or metastases may be detected.
Upon recheck lab work that shows hypercalcemia.
Initial evaluation of a dog that is suspected to have an anal sac tumor should include a blood cell count and blood chemistries (particularly to evaluate blood calcium and phosphorus levels and kidney function) and ultrasound or X-ray examination of the abdomen to look for evidence of tumor spread to the pelvic lymph nodes. Dogs can have fairly small tumors in the anal sac and still have very enlarged lymph nodes. Chest X-rays might also be helpful because these tumors can also spread to the lungs.
Surgery is the first treatment approach. If the primary tumor is amenable to surgery, it should be removed. While this is unlikely to result in cure because these tumors tend to spread early in the course of disease, it might provide a significant disease-free interval with a good quality of life . The goals of surgery are to minimize symptoms and to return the blood calcium to normal if it is elevated. If the lymph nodes are enlarged, they can be removed as well. Surgery in these areas can be technically challenging and might require a surgical specialist. The benefits of surgery must be weighed against the risk of complications.
Radiation therapy can be used to control both the primary tumor and associated lymph nodes. It can be used alone or in combination with surgery, depending on the particular dog in question. Similarly, chemotherapy might be useful (either alone or in combination with other treatments) in causing regression of the tumor or delaying the progression of the disease. However, more studies need to be done to more fully define the best treatment protocols for this tumor. Treatment decisions are based on a thorough evaluation of each individual case and the clinical judgment of the oncologist and/or surgeon.
Unfortunately, regardless of treatment, most dogs will still eventually succumb to this tumor. For dogs treated with surgery alone, average survival times are about 9 months, with a range of several weeks to over three years. Some early anecdotal reports suggest that an aggressive combination of surgery, radiation and chemotherapy might improve on these results, but this remains to be confirmed.
Time to metastases in most cases was at least several months and often 9-12 months following the first or second surgery. Follow up visits with rectal palpation were variable. Dogs generally presented with a history of tenesmus and or constipation problems. Dogs may have a history of abnormal eliminations with ribbon-like stool or smaller than normal size or droppings from one angle. Local recurrence was often accompanied by the presence of a large sub-lumbar mass obstructing the distal colon.
Some dogs present with deep sphincter recurrence along with the sublumbar lymphadenopathy six to 9 months post initial surgery. Panels on these dogs do not show abnormalities in calcium levels.
Most of the dogs were suspected to have routine perianal tumors and there is no way to tell the malignant tumors apart from the benign ones, unless they are biopsied.
The end result to consider is that 50% recur after attempts to control them by castration and dogs die of metastases to the sublumbar lymph nodes. With these events in mind, I recommend a more analytical approach and a more rigid follow up program to scout for recurrent perianal tumors in senior male dogs.
IN FEMALE DOGS:
Hypercalcemia is a tell tale marker for anal sac carcinoma in female dogs. If the dog does not exhibit the enlarged lymph nodes which are characteristic of lymphoma, a search for anal sac carcinoma is indicated. Anal sac carcinomas should be considered very aggressive from the start. Even small tumors release cancer cells that travel forward involving the dorsal rectal nodes, the sublumbar and illiac lymph node chain.
Affected dogs must be treated for malignant hypercalcemia with saline diuresis and monitored closely during and post surgically. Once the primary tumor is exised, the calcium level returns to normal. Recurrence or metastases may be detected.
Upon recheck lab work that shows hypercalcemia.
Initial evaluation of a dog that is suspected to have an anal sac tumor should include a blood cell count and blood chemistries (particularly to evaluate blood calcium and phosphorus levels and kidney function) and ultrasound or X-ray examination of the abdomen to look for evidence of tumor spread to the pelvic lymph nodes. Dogs can have fairly small tumors in the anal sac and still have very enlarged lymph nodes. Chest X-rays might also be helpful because these tumors can also spread to the lungs.
Surgery is the first treatment approach. If the primary tumor is amenable to surgery, it should be removed. While this is unlikely to result in cure because these tumors tend to spread early in the course of disease, it might provide a significant disease-free interval with a good quality of life . The goals of surgery are to minimize symptoms and to return the blood calcium to normal if it is elevated. If the lymph nodes are enlarged, they can be removed as well. Surgery in these areas can be technically challenging and might require a surgical specialist. The benefits of surgery must be weighed against the risk of complications.
Radiation therapy can be used to control both the primary tumor and associated lymph nodes. It can be used alone or in combination with surgery, depending on the particular dog in question. Similarly, chemotherapy might be useful (either alone or in combination with other treatments) in causing regression of the tumor or delaying the progression of the disease. However, more studies need to be done to more fully define the best treatment protocols for this tumor. Treatment decisions are based on a thorough evaluation of each individual case and the clinical judgment of the oncologist and/or surgeon.
Unfortunately, regardless of treatment, most dogs will still eventually succumb to this tumor. For dogs treated with surgery alone, average survival times are about 9 months, with a range of several weeks to over three years. Some early anecdotal reports suggest that an aggressive combination of surgery, radiation and chemotherapy might improve on these results, but this remains to be confirmed.
web sites of interest:
http://www.caninecancerawareness.org
http://www.caninecancerawareness.org/CanineCancerAdenocarcinoma.html
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