Title: Mammary tumor

{{Short description|Type of veterinary cancer in mammals}}
{{For|mammary tumors in humans|breast cancer}}
[[Image:Mammary tumor.JPG|thumb|Mammary tumor in a dog]]
A '''mammary tumor''' is a [[neoplasm]] originating in the [[mammary gland]]. It is a common finding in older female [[dog]]s and [[cat]]s that are not [[spaying and neutering|spay]]ed, but they are found in other animals as well. The mammary glands in dogs and cats are associated with their [[nipple]]s and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and [[breast cancer]] in humans, including [[tumor]] type, [[malignant|malignancy]], and treatment options. The [[prevalence]] in dogs is about three times that of women.&lt;ref name=Merck&gt;{{cite web | title = Mammary Tumors: Introduction | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/112300.htm | accessdate = 2007-03-21 | archive-date = 2007-02-27 | archive-url = https://web.archive.org/web/20070227151845/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F112300.htm | url-status = dead }}&lt;/ref&gt; In dogs, mammary tumors are the second most common tumor (after skin tumors) over all and the most common tumor in female dogs&lt;ref&gt;{{cite journal |vauthors=Benjamin S, Lee A, Saunders W |title=Classification and behavior of canine mammary epithelial neoplasms based on life-span observations in beagles |journal=Vet Pathol |volume=36 |issue=5 |pages=423–36 |year=1999 |pmid=10490210 |doi=10.1354/vp.36-5-423}}&lt;/ref&gt; with a reported incidence of 3.4%.&lt;ref name=&quot;akcchf.org&quot;&gt;{{cite web | title = Determining The Best Age At Which To Spay Or Neuter | year = 2008 | url = http://www.akcchf.org/canine-health/your-dogs-health/determining-the-best-age-at.html | format = PDF | access-date = 2010-12-22 | archive-url = https://web.archive.org/web/20151208094744/http://www.akcchf.org/canine-health/your-dogs-health/determining-the-best-age-at.html | archive-date = 2015-12-08 | url-status = dead }}&lt;/ref&gt; Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with female dogs left intact, those spayed before puberty have 0.5% of the risk, those spayed after one estrous cycle have 8.0% of the risk, and dogs spayed after two estrous cycles have 26.0% of the risk of developing mammary neoplasia later in life. Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed. While the benefit of spaying decreases with each estrous cycle, some benefit has been demonstrated in female dogs even up to 9 years of age.&lt;ref name=&quot;akcchf.org&quot;/&gt; There is a much lower risk (about 1 percent) in male dogs and a risk in cats about half that of dogs.&lt;ref name=Jolle&gt;{{cite web | last = Kirpensteijn | first = Jolle | author2 = Rutteman, Gerard R. | title = Practical treatment of mammary neoplasia | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = http://www.ivis.org/proceedings/navc/2006/SAE/281.pdf?LA=1 | format = PDF | accessdate = 2007-03-21 | archive-url = https://web.archive.org/web/20070929105913/http://www.ivis.org/proceedings/navc/2006/SAE/281.pdf?LA=1 | archive-date = 2007-09-29 | url-status = dead }}&lt;/ref&gt;

==In dogs==
[[File:Lexhe magnant må tetes lon.jpg|thumb|[[Emaciation|Emaciated]] female dog with a 9-month-old mammary tumor.]]
[[File:Lexhe magnant må tetes près.jpg|thumb|The same, closer]]
[[File:Metastasized canine mammary carcinoma legended.svg|thumb|[[Radiography|Radiograph]] (x-ray) of an affected dog. The metastases cause the dog difficulty in breathing.]]

===Causes===
The exact causes for the development of canine mammary tumors are not fully understood.&lt;ref name=Klopfleisch/&gt; However, hormones of the estrous cycle seem to be involved. Female dogs who are not spayed or who are spayed later than the first [[estrus cycle|heat cycle]] are more likely to develop mammary tumors. Dogs have an overall reported incidence of mammary tumors of 3.4 percent. Dogs spayed before their first heat have 0.5 percent of this risk, and dogs spayed after just one heat cycle have 8 percent of this risk.&lt;ref name=Merck/&gt; The tumors are often multiple. The average age of dogs with mammary tumors is ten to eleven years old.&lt;ref name=Schafer&gt;{{cite journal |doi=10.1177/030098589803500302 |vauthors=Schafer K, Kelly G, Schrader R, Griffith W, Muggenburg B, Tierney L, Lechner J, Janovitz E, Hahn F |title=A canine model of familial mammary gland neoplasia |journal=Vet Pathol |volume=35 |issue=3 |pages=168–77 |year=1998 |pmid=9598580|doi-access=free }}&lt;/ref&gt; [[Obesity]] at one year of age and eating [[red meat]] have also been associated with an increased risk for these tumors,&lt;ref&gt;{{cite journal |doi=10.1111/j.1939-1676.1998.tb02108.x |vauthors=Pérez Alenza D, Rutteman G, Peña L, Beynen A, Cuesta P |title=Relation between habitual diet and canine mammary tumors in a case-control study |journal=J Vet Intern Med |volume=12 |issue=3 |pages=132–9 |year=1998 |pmid=9595373|doi-access=free }}&lt;/ref&gt; as has the feeding of high fat homemade diets.&lt;ref&gt;{{cite web | last = Sirivaidyapong | first = S. | title = Dogs with Mammary Gland Tumors and the Feeding Dietary Types | work = Proceedings of the 28th World Congress of the World Small Animal Veterinary Association | year = 2003 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2003&amp;PID=6801&amp;O=Generic | accessdate = 2007-03-21 }}&lt;/ref&gt; 
There are several hypotheses on the molecular mechanisms involved in the development of canine mammary tumors but a specific genetic mutation has not been identified.&lt;ref name=Klopfleisch/&gt;

===Biology===
Historically, about 50 percent of mammary tumors in dogs were found to be malignant,&lt;ref name=Ettinger_1995&gt;{{cite book |author1=Ettinger, Stephen J. |author2=Feldman, Edward C. |title=Textbook of Veterinary Internal Medicine |edition=4th |publisher=W.B. Saunders Company |year=1995 |isbn=978-0-7216-6795-9}}&lt;/ref&gt; although taking into account tumor behavior, one study has estimated true malignancy in mammary tumors to be 21 to 22 percent.&lt;ref name=Schafer/&gt; [[Adenoma]]s and [[fibroadenoma]]s make up the [[benign]] types. Malignant mammary tumors are divided into [[sarcoma]]s, [[carcinosarcoma]]s, [[inflammatory carcinoma]]s (usually [[anaplastic carcinoma]]s), and [[carcinoma]]s (including [[adenocarcinoma]]s), which are the most common.&lt;ref name=Ettinger_1995/&gt; Inflammatory carcinomas describe tumors that are fast growing and have bruising, [[edema]], and pain, and can also cause [[disseminated intravascular coagulation]]. They are the most malignant type of canine mammary tumor.&lt;ref&gt;{{cite web |last1=Nieto |first1=Ana |last2=Peña |first2=Laura |last3=Silvan |first3=Gema |last4=Perez-Alenza |first4=Maria Dolores |last5=Illera |first5=Juan Carlos |title=Serum Hormone Profile of Canine Inflammatory Carcinoma |work=Proceedings of the 27th World Congress of the World Small Animal Veterinary Association |year=2002 |url=http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2002&amp;PID=2847 |accessdate=2007-03-21}}&lt;/ref&gt;

Malignant tumors are also subdivided [[histopathology|histopathologically]] into those showing [[blood vessel]] wall invasion and those that do not. Without blood vessel wall invasion there is a better [[prognosis]].&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=978-0-683-06105-5}}&lt;/ref&gt; Dogs with noninvasive adenocarcinomas have an average survival time of two years, while dogs with invasive adenocarcinomas have an average survival time of one year.&lt;ref name=Morrison_1998/&gt; Tumor size also affects the prognosis, in that dogs with tumors greater than five centimeters have a greater chance of [[lymph node]] [[metastasis]].&lt;ref name=Chang&gt;{{cite journal |vauthors=Chang S, Chang C, Chang T, Wong M |title=Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumors: 79 cases (1998-2002) |journal=J Am Vet Med Assoc |volume=227 |issue=10 |pages=1625–9 |year=2005 |pmid=16313041 |doi=10.2460/javma.2005.227.1625|doi-access=free }}&lt;/ref&gt; Tumor type is also important. Sarcomas and carcinosarcomas carry an average survival time of nine to twelve months.&lt;ref name=Ettinger_1995/&gt; Inflammatory carcinomas have a very poor prognosis, and have usually metastasized by the time of diagnosis.&lt;ref name=Ettinger_1995/&gt; Metastasis for any malignant mammary tumor is usually to the regional lymph nodes and [[lung]]s.&lt;ref name=Morrison_1998/&gt;

The molecular carcinogenesis of canine mammary tumors are not completely understood. However, the increasing information on molecular pathways involved in the carcinogenesis of this canine tumor has potential to complement and refine the current diagnostic and therapeutic approach to this tumor type.&lt;ref name=Klopfleisch&gt;{{cite journal |vauthors=Klopfleisch R, von Euler H, Sarli G, Pinho SS, Gärtner F, Gruber AD |title=Molecular Carcinogenesis of Canine Mammary Tumors: News From an Old Disease |journal=Veterinary Pathology |volume= 48|issue=1 |pages= 98–116|year=2010 |pmid=21149845 |doi=10.1177/0300985810390826}}&lt;/ref&gt; Furthermore, current data show that significant similarities and differences exist between canine and human mammary tumors at the molecular level.&lt;ref name=Klopfleisch1&gt;{{cite journal |vauthors=Klopfleisch R, Klose P, Weise C, Bondzio A, Multhaup G, Einspanier R, Gruber AD |title=Proteome of metastatic canine mammary carcinomas: similarities to and differences from human breast cancer.|journal=J Proteome Res |volume=9 |issue=12 |pages=6380–91 |year=2010 |pmid=20932060 |doi=10.1021/pr100671c}}&lt;/ref&gt;&lt;ref name=Klopfleisch2/&gt;

===Diagnosis and treatment===
Appearance and location of the tumor is enough to identify it as a mammary tumor. [[Biopsy]] will give type and invasiveness of the tumor. In addition, newer studies showed that certain gene expression patterns are associated with malignant behaviour of canine mammary tumors.&lt;ref name=Klopfleisch/&gt;&lt;ref name=Klopfleisch1/&gt;&lt;ref name=Klopfleisch2&gt;{{cite journal |vauthors=Klopfleisch R, Lenze D, Hummel M, Gruber AD |title=Metastatic canine mammary carcinomas can be identified by a gene expression profile that partly overlaps with human breast cancer profiles.|journal=BMC Cancer |volume=10|pages=618 |year=2010 |pmid=21062462 |pmc=2994823 |doi=10.1186/1471-2407-10-618 |doi-access=free }}&lt;/ref&gt;&lt;ref name=Klopfleisch3&gt;{{cite journal |vauthors=Klopfleisch R, Lenze D, Hummel M, Gruber AD |title=The metastatic cascade is reflected in the transcriptome of metastatic canine mammary carcinomas.|journal=Veterinary Journal|volume= 190|issue= 2|pages= 236–243|year=2010 |pmid=21112801 |doi=10.1016/j.tvjl.2010.10.018}}&lt;/ref&gt;&lt;ref name=Klopfleisch4&gt;{{cite journal |vauthors=Klopfleisch R, Klose P, Gruber AD |title=The combined expression pattern of BMP2, LTBP4, and DERL1 discriminates malignant from benign canine mammary tumors.|journal=Veterinary Pathology |volume=47 |issue=3 |pages=446–54 |year=2010 |pmid=20375427 |doi=10.1177/0300985810363904}}&lt;/ref&gt;

Surgical removal is the treatment of choice, but chest [[x-ray]]s should be taken first to rule out metastasis. Removal should be with wide margins to prevent recurrence, taking the whole mammary gland if necessary. Because 40 to 50 percent of dog mammary tumors have [[estrogen receptor]]s,&lt;ref name=Morrison_1998/&gt; spaying is recommended by many [[veterinarian]]s. A recent study showed a better prognosis in dogs that are spayed at the time of surgery or that had been recently spayed.&lt;ref name=Chang/&gt; However, several other studies found no improvement of disease outcome when spaying was performed after the tumor had developed. [[Chemotherapy]] is rarely used.&lt;ref name=Jolle/&gt;

===Breeds at increased risk===
*[[Chihuahua (dog)|Chihuahua]]
*[[Poodle]]
*[[Brittany Spaniel]]
*[[English Setter]]
*[[Pointer (dog)|Pointer]]
*[[Fox Terrier]]
*[[Boston Terrier]]
*[[Cocker Spaniel]]&lt;ref name=Ettinger_1995/&gt;
*[[Lhasa Apso]]

==In cats==
Mammary tumors are the third most common neoplasia in cats, following lymphoid and skin cancers.&lt;ref name=Canvet&gt;{{cite journal |vauthors=Viste J, Myers S, Singh B, Simko E |title=Feline mammary adenocarcinoma: tumor size as a prognostic indicator |journal=Can Vet J |volume=43 |issue=1 |pages=33–7 |year=2002 |pmid=11802667 |pmc=339085}}&lt;/ref&gt; The incidence of mammary tumors in cats is reduced by 91 percent in cats spayed prior to six months of age and by 86 percent in cats spayed prior to one year, according to one study.&lt;ref&gt;{{cite journal |vauthors=Overley B, Shofer F, Goldschmidt M, Sherer D, Sorenmo K |title=Association between ovarihysterectomy and feline mammary carcinoma |journal=J Vet Intern Med |volume=19 |issue=4 |pages=560–3 |year=2005 |pmid=16095174 |doi=10.1892/0891-6640(2005)19[560:ABOAFM]2.0.CO;2 |issn=0891-6640|doi-access= }}&lt;/ref&gt; [[Siamese cat]]s and Japanese breeds seem to have increased risk,&lt;ref&gt;{{cite journal |vauthors=Ito T, Kadosawa T, Mochizuki M, Matsunaga S, Nishimura R, Sasaki N |title=Prognosis of malignant mammary tumor in 53 cats |journal=J Vet Med Sci |volume=58 |issue=8 |pages=723–6 |year=1996 |pmid=8877968 |doi=10.1292/jvms.58.723|doi-access=free }}&lt;/ref&gt; and obesity also appears to be a factor in tumor development.&lt;ref&gt;{{cite journal |author=German A |title=The growing problem of obesity in dogs and cats |journal=J Nutr |volume=136 |issue=7 Suppl |pages=1940S–1946S |year=2006 |pmid=16772464|doi=10.1093/jn/136.7.1940S |doi-access=free }}&lt;/ref&gt; Malignant tumors make up 80 to 96 percent of mammary tumors in cats, almost all adenocarcinomas.&lt;ref&gt;{{cite journal |vauthors=Millanta F, Lazzeri G, Mazzei M, Vannozzi I, Poli A |title=MIB-1 labeling index in feline dysplastic and neoplastic mammary lesions and its relationship with postsurgical prognosis |journal=Vet Pathol |volume=39 |issue=1 |pages=120–6 |year=2002 |pmid=12102203 |doi=10.1354/vp.39-1-120|doi-access=free }}&lt;/ref&gt; Male cats may also develop mammary adenocarcinoma, albeit rarely, and the clinical course is similar to female cats.&lt;ref&gt;{{cite journal |vauthors=Skorupski K, Overley B, Shofer F, Goldschmidt M, Miller C, Sørenmo K |title=Clinical characteristics of mammary carcinoma in male cats |journal=J Vet Intern Med |volume=19 |issue=1 |pages=52–5 |year=2005 |pmid=15715048 |doi=10.1892/0891-6640(2005)19&lt;52:CCOMCI&gt;2.0.CO;2 |issn=0891-6640|doi-access=free }}&lt;/ref&gt; As in dogs, tumor size is an important prognostic factor, although for tumors less than three centimeters the individual size is less predictive. According to one study, cats with tumors less than three cm had an average survival time of 21 months, and cats with tumors greater than three cm had an average survival of 12 months.&lt;ref name=Canvet/&gt; About 10 percent of cat mammary tumors have estrogen receptors, so spaying at the time of surgery has little effect on recurrence or survival time.&lt;ref name=Morrison_1998/&gt; Metastasis tends to be to the lungs and lymph nodes, and rarely to bone.&lt;ref&gt;{{cite journal |vauthors=Waters D, Honeckman A, Cooley D, DeNicola D |title=Skeletal metastasis in feline mammary carcinoma: case report and literature review |journal=J Am Anim Hosp Assoc |volume=34 |issue=2 |pages=103–8 |year=1998 |pmid=9507421|doi=10.5326/15473317-34-2-103 }}&lt;/ref&gt; Diagnosis and treatment is similar to the dog. There is a better prognosis with bilateral radical surgery (removing both mammary chains) than with more conservative surgery.&lt;ref&gt;{{cite journal |vauthors=Novosad C, Bergman P, O'brien M, McKnight J, Charney S, Selting K, Graham J, Correa S, Rosenberg M, Gieger T |title=Retrospective Evaluation of Adjunctive Doxorubicin for the Treatment of Feline Mammary Gland Adenocarcinoma: 67 Cases |journal=J Am Anim Hosp Assoc |volume=42 |issue=2 |pages=110–120 |year=2006 |pmid=16527911 |doi=10.5326/0420110}}&lt;/ref&gt; [[Doxorubicin]] has shown some promise in treatment.&lt;ref&gt;{{cite web | last = Moore | first = Anthony | title = Advances in the treatment of mammary neoplasia | work = Proceedings of the 31st World Congress of the World Small Animal Veterinary Association | year = 2004 | url = https://www.ivis.org/proceedings/wsava/2006/lecture20/Moore2.pdf?LA=1 | format = PDF | accessdate = 2007-03-21 }}&lt;/ref&gt;

==In rats==
[[File:Rat Mammary Cyst.JPG|thumb|A mammary tumor in a rat.]]
Most mammary tumors in [[rat]]s are benign fibroadenomas, which are also the most common tumor in the rat.&lt;ref name=Green&gt;{{cite journal |author=Greenacre C |title=Spontaneous tumors of small mammals |journal=Vet Clin North Am Exot Anim Pract |volume=7 |issue=3 |pages=627–51, vi |year=2004 |pmid=15296867 |doi=10.1016/j.cvex.2004.04.009}}&lt;/ref&gt; Less than 10 percent are adenocarcinomas.&lt;ref name=Hillyer_1997/&gt;  They occur in male and female rats. The tumors can be large and occur anywhere on the trunk.&lt;ref name=Merckrodent/&gt; There is a good prognosis with surgery.&lt;ref&gt;{{cite web|author1=Pritchett, K.R.|author2=Corning, B.F.|year=2006|title=Biology and Medicine of Rats|work=Laboratory Animal Medicine and Management|url=http://www.ivis.org/advances/Reuter/corning/chapter_frm.asp?LA=1|accessdate=2007-03-21|archive-url=https://web.archive.org/web/20090212235738/http://www.ivis.org/advances/Reuter/corning/chapter_frm.asp?LA=1|archive-date=2009-02-12|url-status=dead}}&lt;/ref&gt; Spayed rats have a decreased risk of developing mammary tumors.&lt;ref&gt;{{cite web | last = Capello | first = Vittorio | title = Clinical and surgical approach to common diseases of pet rodents | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = https://www.ivis.org/proceedings/navc/2006/SAE/612.pdf?LA=1 | format = PDF | accessdate = 2007-03-21 }}&lt;/ref&gt;

==In mice==
Most mammary tumors in [[mouse|mice]] are adenocarcinomas. They can be caused by viral infection.&lt;ref name=Hillyer_1997/&gt; Recurrence rates are high, and therefore there is a poor prognosis. There is frequently local tissue invasion and metastasis to the lungs.&lt;ref name=Merckrodent&gt;{{cite web | title = Rats and Mice: Neoplasia | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/171562.htm | accessdate = 2007-03-21 | archive-date = 2006-10-16 | archive-url = https://web.archive.org/web/20061016120634/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F171562.htm | url-status = dead }}&lt;/ref&gt; A well known tumor virus of the mouse is the [[mouse mammary tumor virus]], which may be the most common cause of this tumor in mice.&lt;ref&gt;{{cite journal |vauthors=Szabo S, Haislip A, Garry R |title=Of mice, cats, and men: is human breast cancer a zoonosis? |journal=Microsc Res Tech |volume=68 |issue=3–4 |pages=197–208 |year=2005 |pmid=16276516 |doi=10.1002/jemt.20232|doi-access=free }}&lt;/ref&gt;

==In other animals==

*Ferrets: Mammary tumors are rare in [[ferret]]s. Appearance tends to be a soft, dark colored lump. Most seem to be benign and occur most frequently in neutered males. Surgery is recommended.
*Guinea pigs: Mammary tumors in [[guinea pig]]s occur in males and females. Most are benign, but 30 percent are adenocarcinomas.&lt;ref name=Hillyer_1997&gt;{{cite book|author1=Hillyer, Elizabeth V. |author2=Quesenberry, Katherin E. |title=Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery|edition=1st|publisher=W.B. Saunders Company|year=1997|isbn=978-0-7216-4023-5}}&lt;/ref&gt; They usually do not metastasize, but aggressive surgery is necessary to prevent recurrence.
*Hamsters and gerbils: Mammary tumors tend to be benign in [[hamster]]s and malignant in [[gerbil]]s.{{citation needed|date=July 2017}}
*Hedgehogs: Mammary gland adenocarcinoma is the most common tumor of the [[hedgehog]].&lt;ref name=Green/&gt;

==References==
{{reflist|colwidth=35em}}

{{DEFAULTSORT:Mammary tumor}}
[[Category:Types of animal cancers]]
[[Category:Cancer in dogs]]
[[Category:Cancer in cats]]