Anal sac adenocarcinoma

An anal sac adenocarcinoma is an uncommon and aggressive malignant tumor found in dogs that arises from the tissue of anal sac. At least one case has been reported in a cat. [cite journal |author=Mellanby R, Foale R, Friend E, Woodger N, Herrtage M, Dobson J |title=Anal sac adenocarcinoma in a Siamese cat |journal=J Feline Med Surg |volume=4 |issue=4 |pages=205–7 |year=2002 |pmid=12468314 |doi=10.1053/jfms.2002.0174] They are the second most common cancerous cause of hypercalcaemia (high serum calcium) in dogs.cite journal | last = Lucas | first = Pamela | coauthors = Lacoste, Hugues; de Lorimier, Louis-Phillipe; Fan, Timothy M. | title = Treating paraneoplastic hypercalcemia in dogs and cats | journal = Veterinary Medicine | volume = 102 | issue = 5 | pages = 314–331 | publisher = Advanstar Communications | month = May | year = 2007 ]

igns and symptoms

Anal sac adenocarcinomas first appear as a small lump associated with one of the anal sacs, but they can grow to a large size. Smaller tumors are undetectable without a rectal examination, while larger tumors can cause pain and straining to defecate. Between 25 and 50 percent of dogs with these tumors will also develop hypercalcaemia [cite journal |author=Kadar E, Rush J, Wetmore L, Chan D |title=Electrolyte disturbances and cardiac arrhythmias in a dog following pamidronate, calcitonin, and furosemide administration for hypercalcemia of malignancy |journal=J Am Anim Hosp Assoc |volume=40 |issue=1 |pages=75–81 |year=2004 |pmid=14736909] through secretion of parathyroid hormone-related protein by the tumor. [cite journal |author=Gröne A, Werkmeister J, Steinmeyer C, Capen C, Rosol T |title=Parathyroid hormone-related protein in normal and neoplastic canine tissues: immunohistochemical localization and biochemical extraction |journal=Vet Pathol |volume=31 |issue=3 |pages=308–15 |year=1994 |pmid=8053125] Symptoms of hypercalcaemia include increased drinking and urination, vomiting, loss of appetite, weight loss, and bradycardia (slow heart rate). Anal sac adenocarcinomas also have a tendency to metastasize to the lymph nodes, spleen, and lungs.cite book|author=Morrison, Wallace B.|title=Cancer in Dogs and Cats|edition=1st ed.|publisher=Williams and Wilkins|year=1998|id=ISBN 0-683-06105-4] The sublumbar (iliac) lymph nodes are the most common site of metastasis and can become larger than the original tumor. [cite web | last = Kessler | first = Martin | title = Anal sac carcinoma in the dog | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = http://www.ivis.org/proceedings/navc/2006/SAE/278.pdf?LA=1 | format = PDF | accessdate = 2007-03-29 ]

Diagnosis

Anal sac adenocarcinomas are often suspected due to location and behavior, but a biopsy is necessary for a definitive diagnosis. Needle aspiration biopsy is a common first step. Cytology reveals clusters of cells with uniform round nuclei. These cells do not have many of the features usually associated with malignancy, such as a high nucleus to cytoplasm ratio or prominent nucleoli.cite journal | last = Cronin | first = Kim L. | title = Apocrine gland adenocarcinoma of the anal sac | journal = DVM | pages = 2S–6S | publisher = Advanstar Communications | month = December | year = 2007 ] Ultrasonography and radiography are performed to look for metastasis.

Treatment and prognosis

Aggressive surgical removal of the tumor and any enlarged sublumbar lymph nodes is essential for treatment of the tumor and associated hypercalcaemia. There is a high recurrence rate, although removal of lymph nodes with metastasis may improve survival time. [cite journal |author=Hobson H, Brown M, Rogers K |title=Surgery of metastatic anal sac adenocarcinoma in five dogs |journal=Vet Surg |volume=35 |issue=3 |pages=267–70 |year=2006 |pmid=16635006 |doi=10.1111/j.1532-950X.2006.00137.x] Radiation therapy and chemotherapy may be helpful in treatment. Severe hypercalcaemia is treated with aggressive IV fluid therapy using sodium chloride and medications such as loop diuretics (increased kidney excretion of calcium) and aminobisphosphonates (decreased calcium release from bones). A poorer prognosis is associated with large tumor size (greater than 10 cm), hypercalcaemia, and generalized metastasis. [cite web | last = Kirpensteijn | first = Jolle | title = Treatment of perianal and anal sac tumors | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = http://www.ivis.org/proceedings/navc/2006/SAE/280.pdf?LA=1 | format = PDF | accessdate = 2007-03-29 ]

Commonly affected breeds

Breeds that may be more commonly affected include the English Cocker Spaniel, German Shepherd Dog, Alaskan Malamute, Dachshund, and Springer Spaniel. [cite web | title = Apocrine Gland Tumors of Anal Sac Origin | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/72209.htm | accessdate = 2007-01-01 ]

References

External links

* [http://www.petcancercenter.org/Cancer_Types_Anal_Sac.html "Anal Sac Tumors in Cats and Dogs" from Pet Cancer Center]
* [http://www.vetspecialists.co.uk/06_Animal_Welfare/Oncology_Facts/Anal_Sac_Gland_Carcinoma.html "Anal sac gland carcinoma: veterinary factsheet" from Davies Veterinary Specialists]