Title: Anal sac adenocarcinoma

{{Short description|Malignant tumor found in dogs}}
{{See also|Perianal gland tumor}}
[[Image:Anal sac adenocarcinoma cytology.JPG|thumb|Cytology of an anal sac adenocarcinoma]]
An '''anal sac adenocarcinoma''' is an uncommon and aggressive [[malignant]] [[tumor]] found in [[dog]]s that arises from the apocrine glandular tissue of [[anal glands|anal sac]].    The disease exists in cats as well, but is much less common in that species.&lt;ref&gt;{{cite journal |vauthors=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|pmc=10822394 }}&lt;/ref&gt;  They are the second most common cancerous cause of [[hypercalcaemia]] (high serum [[calcium]]) in dogs, following T-cell lymphoma.&lt;ref name=VetMed&gt;{{cite journal | last = Lucas | first = Pamela |author2= Lacoste, Hugues|author3= de Lorimier, Louis-Phillipe|author4= Fan, Timothy M. | title = Treating paraneoplastic  hypercalcemia in dogs and cats | journal = Veterinary Medicine | volume = 102 | issue = 5 | pages = 314–331 | publisher = Advanstar Communications |date=May 2007 }}&lt;/ref&gt;

==Signs and symptoms==
Apocrine gland anal sac adenocarcinomas first appear as small lumps associated with one of the anal sacs (rarely bilateral), 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 40 percent of dogs with these tumors will also develop hypercalcaemia&lt;ref&gt;{{cite journal |vauthors=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}}&lt;/ref&gt; through secretion of [[parathyroid hormone-related protein]] by the tumor.&lt;ref&gt;{{cite journal |vauthors=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 |doi=10.1177/030098589403100303|doi-access=free }}&lt;/ref&gt;  Symptoms of hypercalcaemia include increased drinking and urination, vomiting, loss of appetite, weight loss, and [[bradycardia]] (slow heart rate).  Apocrine gland anal sac adenocarcinomas also have a tendency to [[metastasis|metastasize]] to the regional [[lymph node]]s, [[spleen]], and eventually [[lung]]s and, less commonly, bones.&lt;ref name=Morrison_1998&gt;{{cite book|author=Morrison, Wallace B.|title=Cancer in Dogs and Cats|edition=1st|publisher=Williams and Wilkins|year=1998|isbn=0-683-06105-4}}&lt;/ref&gt;  The sublumbar ([[Internal iliac lymph nodes|iliac]]) lymph nodes are the most common site of metastasis and can become larger than the original tumor.&lt;ref&gt;{{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 |url-status=dead |archiveurl=https://web.archive.org/web/20070927032240/http://www.ivis.org/proceedings/navc/2006/SAE/278.pdf?LA=1 |archivedate=2007-09-27 }}&lt;/ref&gt;

==Diagnosis==
Anal sac adenocarcinomas are often suspected due to location (palpable masse in anal sac) and behavior, but a [[biopsy]] and [[histopathology]] is necessary for a definitive diagnosis.  [[Fine needle aspiration]] and [[cytology]] is a common first step.  [[Cytopathology]] reveals clusters of [[cell (biology)|cell]]s with uniform round [[cell nucleus|nuclei]].  These cells do not have many of the features usually associated with malignancy, such as a high nucleus to [[cytoplasm]] ratio or prominent [[nucleolus|nucleoli]].&lt;ref name=Cronin&gt;{{cite journal | last = Cronin | first = Kim L. | title = Apocrine gland adenocarcinoma of the anal sac | journal = DVM | pages = 2S–6S | publisher = Advanstar Communications |date=December 2007 }}&lt;/ref&gt;  [[Medical ultrasonography|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.&lt;ref&gt;{{cite journal |vauthors=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}}&lt;/ref&gt;  [[Radiation therapy]] and [[chemotherapy]] may be helpful in treatment.  Severe hypercalcaemia is treated with aggressive [[Intravenous therapy|IV fluid therapy]] using [[sodium chloride]] and medications such as [[loop diuretic]]s (increased kidney excretion of calcium) and [[Bisphosphonate|aminobisphosphonate]]s (decreased calcium release from bones).&lt;ref name=VetMed/&gt;  A poorer prognosis is associated with large tumor size (greater than 10 cm), hypercalcaemia, and distante metastasis.&lt;ref&gt;{{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 |url-status=dead |archiveurl=https://web.archive.org/web/20070929105056/http://www.ivis.org/proceedings/navc/2006/SAE/280.pdf?LA=1 |archivedate=2007-09-29 }}&lt;/ref&gt;  Early, incidental diagnosis of small anal sac masses may lead to a better prognosis with surgery alone (ongoing study).

==Commonly affected breeds==
Breeds that may be more commonly affected include the [[English Cocker Spaniel]], [[German Shepherd Dog]], [[Alaskan Malamute]], [[Dachshund]], and [[English Springer Spaniel|Springer Spaniel]].&lt;ref&gt;{{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 }}&lt;/ref&gt;  It is a disease of middle-age to older dogs and even though early reports described spayed females as more commonly affected, multiple recent studies have shown no gender overrepresentation. 

==References==
{{Reflist}}

==External links==
*[http://www.petcancercenter.org/Cancer_Types_Anal_Sac.html ''Anal Sac Tumors in Cats and Dogs'' from Pet Cancer Center]
*[https://web.archive.org/web/20080517111747/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]
*[https://web.archive.org/web/20101108085147/http://www.dogcancerblog.com/bladder-and-prostate-cancer-neutering-male-dogs-increases-risk-2/ ''Bladder and Prostate Cancer: Neutering Male Dogs Increases Risk'' from Dog Cancer Blog]

[[Category:Cancer in dogs]]