Title: Mastocytoma

{{For|mastocytomas in dogs|Mastocytoma in dogs}}
{{Infobox medical condition
| name            = Mastocytoma 
| synonyms        = Mast cell tumor
| image           = Mast cell tumor cytology 2.JPG
| caption         = Mast cell tumor cytology
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| field           = [[Oncology]] 
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A '''mastocytoma''' or '''mast cell tumor''' is  a type of [[Desmoplastic small-round-cell tumor|round-cell tumor]] consisting of [[mast cell]]s.  It is found in humans and many animal species; the term also can refer to an accumulation or [[nodule (medicine)|nodule]] of mast cells that resembles a tumor.

Mast cells originate from the [[bone marrow]] and are normally found throughout the [[connective tissue]] of the body as normal components of the [[immune system]]. As they release [[histamine]], they are associated with [[allergy|allergic reaction]]s.  Mast cells also respond to tissue [[physical trauma|trauma]].  Mast cell [[Granule (cell biology)|granule]]s contain histamine, [[heparin]], [[platelet-activating factor]], and other substances.  Disseminated [[mastocytosis]] is rarely seen in young dogs and cats, while mast cell tumors are usually skin tumors in older dogs and cats. Although not always malignant, they do have the potential to be.  Up to 25 percent of skin tumors in dogs are mast cell tumors,&lt;ref name=saph&gt;{{cite journal |author=Brière C |title=Use of a reverse saphenous skin flap for the excision of a grade II mast cell tumor on the hind limb of a dog |journal=Can Vet J |volume=43 |issue=8 |pages=620–2 |year=2002 |pmid=12170840 |pmc=339404}}&lt;/ref&gt; with a similar number in cats.&lt;ref name=pathol&gt;{{cite journal |vauthors=Johnson T, Schulman F, Lipscomb T, Yantis L |title=Histopathology and biologic behavior of pleomorphic cutaneous mast cell tumors in fifteen cats |journal=Vet Pathol |volume=39 |issue=4 |pages=452–7 |year=2002 |pmid=12126148 |doi=10.1354/vp.39-4-452|s2cid=11717233 }}&lt;/ref&gt;

==Signs and symptoms==
===Humans===
When mastocytomas affect humans, they are typically found in skin.&lt;ref name=Harrisons&gt;{{cite book |veditors=Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J |title=Harrison's principles of internal medicine |chapter=Less Common Hematologic Malignancies |year=2013 |publisher=McGraw-Hill |location=New York |isbn=978-0-07-174889-6 |chapter-url=http://www.accessmedicine.com/content.aspx?aID=9109374 |edition=18th}}&lt;/ref&gt; They usually occur as a single lesion on the trunk or wrist. Although it is rare, mastocytomas are sometimes found in the lung.&lt;ref name=Harrisons /&gt; It can also affect children.&lt;ref&gt;[http://www.pap.es/FrontOffice/PAP/front/Articulos/Articulo/_IXus5l_LjPpSLgsDZd34EA7gozR1zIgX García Iglesias F, Sánchez García AM, García Lara GM. Mastocitoma solitario. Rev Pediatr Aten Primaria. 2014;16:35-7]&lt;/ref&gt;

===Animals===
Mast cell tumors are known among veterinary [[oncologist]]s as 'the great pretenders' because their appearance can be varied, from a [[wart]]-like nodule to a soft subcutaneous lump (similar on palpation to a benign [[lipoma]]) to an [[Skin ulcer|ulcerated]] skin mass.  Most mast cell tumors are small, raised lumps on the skin.  They may be hairless, [[Skin ulcer|ulcerated]], or itchy.  They are usually solitary, but in about six percent of cases, there are multiple mast cell tumors&lt;ref name=Moore&gt;{{cite web | last = Moore | first = Anthony S. | title = Cutaneous Mast Cell Tumors in Dogs | work = Proceedings of the 30th World Congress of the World Small Animal Veterinary Association | year = 2005 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2005&amp;PID=10953&amp;O=Generic | access-date = 2006-08-19 }}&lt;/ref&gt; (especially in Boxers and Pugs).&lt;ref name=Merck/&gt;

Manipulation of the tumor may result in redness and swelling from release of mast cell granules, also known as [[Darier's sign]], and prolonged local hemorrhage.  In rare cases, a highly malignant tumor is present, and signs may include loss of appetite, [[vomiting]], [[diarrhea]], and [[anemia]].  The presence of these signs usually indicates [[mastocytosis]], which is the spread of mast cells throughout the body.  Release of a large amount of histamine at one time can result in ulceration of the [[stomach]] and [[duodenum]] (present in up to 25 percent of cases)&lt;ref name=Merck/&gt; or [[disseminated intravascular coagulation]].  When [[metastasis]] does occur, it is usually to the [[liver]], [[spleen]], [[lymph node]]s and [[bone marrow]].
&lt;gallery&gt;
File:Mast cell tumor side.JPG|Mast cell tumor on the side of a dog
File:Mast cell tumor inner thigh.JPG|Mast cell tumor on the inner thigh of a dog
File:Mast cell tumor of the toe.JPG|Mast cell tumor of the paw
&lt;/gallery&gt;

==Diagnosis==
A [[needle aspiration biopsy]] of the tumor will typically show a large number of mast cells.   This is sufficient to make the diagnosis of a mast cell tumor, although poorly [[cellular differentiation|differentiated]] mast cells may have few granules and thus are difficult to identify.  The granules of the mast cell stain blue to dark purple with a [[Romanowsky stain]], and the cells are medium-sized.&lt;ref&gt;{{cite web | title = Common Cytology Results | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/150210.htm | access-date = 2007-01-27 }}&lt;/ref&gt;  However, a surgical [[biopsy]] is required to find the [[grading (tumors)|grade]] of the tumor.  The grade depends on how well the mast cells are differentiated, [[mitosis|mitotic]] activity, location within the skin, invasiveness, and the presence of [[inflammation]] or [[necrosis]].&lt;ref&gt;{{cite journal | last = Vandis | first = Maria |author2=Knoll, Joyce S. | title = Cytological examination of a cutaneous mast cell tumor in a boxer | journal = Veterinary Medicine | volume = 102 | issue = 3 | pages = 165–168 | publisher = Advanstar Communications |date=March 2007 }}&lt;/ref&gt;
*Grade I – well differentiated and mature cells with a low potential for metastasis
*Grade II – intermediately differentiated cells with potential for local invasion and moderate metastatic behavior
*Grade III – undifferentiated, immature cells with a high potential for metastasis&lt;ref name=saph/&gt;
However, there is a significant amount of discordance between [[veterinary pathologist]]s in assigning grades to mast cell tumors due to imprecise criteria.&lt;ref&gt;{{cite journal |vauthors=Strefezzi R, Xavier J, Catão-Dias J |title=Morphometry of canine cutaneous mast cell tumors |journal=Vet Pathol |volume=40 |issue=3 |pages=268–75 |year=2003 |pmid=12724567 |doi=10.1354/vp.40-3-268|doi-access=free }}&lt;/ref&gt;

The disease is also staged according to the [[WHO]] system:
*Stage I - a single skin tumor with no spread to [[lymph node]]s
*Stage II - a single skin tumor with spread to lymph nodes in the surrounding area
*Stage III - multiple skin tumors or a large tumor invading deep to the skin with or without lymph node involvement
*Stage IV – a tumor with metastasis to the spleen, liver, or bone marrow, or with the presence of mast cells in the blood&lt;ref name=Morrison_1998/&gt;

[[X-ray]]s, [[ultrasound]], or lymph node, bone marrow, or organ biopsies may be necessary to stage the disease.

==Treatment and prognosis==
Removal of the mast cell tumor through surgery is the treatment of choice. [[Antihistamine]]s, such as [[diphenhydramine]], are given prior to surgery to protect against the effects of histamine released from the tumor. Wide margins (two to three centimeters) are required because of the tendency for the tumor cells to be spread out around the tumor. If complete removal is not possible due to the size or location, additional treatment, such as [[radiation therapy]] or [[chemotherapy]], may be necessary. [[Prednisone]] is often used to shrink the remaining tumor portion. [[H₂-receptor antagonist|H2 blocker]]s, such as [[cimetidine]], protect against stomach damage from histamine. [[Vinblastine]] and [[lomustine]] are common chemotherapy agents used to treat mast cell tumors.&lt;ref name=Moore/&gt;

[[Toceranib]] and [[masitinib]], examples of [[receptor tyrosine kinase]] inhibitors, are used in the treatment&lt;ref name=&quot;pmid17227978&quot;&gt;{{cite journal  |vauthors=London CA, Malpas PB, Wood-Follis SL, etal |title=Multi-center, Placebo-controlled, Double-blind, Randomized Study of Oral Toceranib Phosphate (SU11654), a Receptor Tyrosine Kinase Inhibitor, for the Treatment of Dogs with Recurrent (Either Local or Distant) Mast Cell Tumor Following Surgical Excision. |journal=Clin Cancer Res |volume=15 |issue=11 |pages=3856–65 |date=June 2009 |pmid=19470739 |doi= 10.1158/1078-0432.CCR-08-1860 |url=http://clincancerres.aacrjournals.org/cgi/content/abstract/15/11/3856|doi-access=free |url-access=subscription }}&lt;/ref&gt;&lt;ref name=&quot;pmid19789626&quot;&gt;{{cite journal | vauthors = Dubreuil P, Letard S, Ciufolini M, Gros L, Humbert M, Castéran N, Borge L, Hajem B, Lermet A, Sippl W, Voisset E, Arock M, Auclair C, Leventhal PS, Mansfield CD, Moussy A, Hermine O | title = Masitinib (AB1010), a potent and selective tyrosine kinase inhibitor targeting KIT | journal = PLOS ONE | volume = 4 | issue = 9 | article-number = e7258 | date = September 2009 | pmid = 19789626 | pmc = 2746281 | doi = 10.1371/journal.pone.0007258 | bibcode = 2009PLoSO...4.7258D | doi-access = free }}&lt;/ref&gt; of canine [[mast cell]] tumors. Both were recently approved by the [[Food and Drug Administration (United States)|U.S. Food and Drug Administration]] (FDA)&lt;ref&gt;[https://web.archive.org/web/20090603194254/http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm164118.htm  FDA NEWS RELEASE]&lt;/ref&gt;&lt;ref&gt;{{Cite web|url=http://www.prlog.org/11583405-kinavet-is-now-available-from-vetsource.html|title = KINAVET is Now Available from VetSource}}&lt;/ref&gt; as dog-specific anti[[cancer]] drugs.&lt;ref&gt;[https://web.archive.org/web/20090607022806/http://www.cbsnews.com/stories/2009/06/03/eveningnews/main5060208.shtml  CBS News FDA Approves First-Ever Dog Cancer Drug]&lt;/ref&gt;

Grade I or II mast cell tumors that can be completely removed have a good [[prognosis]].  One study showed about 23 percent of incompletely removed grade II tumors recurred locally.&lt;ref&gt;{{cite journal |vauthors=Séguin B, Besancon M, McCallan J, Dewe L, Tenwolde M, Wong E, Kent M |title=Recurrence rate, clinical outcome, and cellular proliferation indices as prognostic indicators after incomplete surgical excision of cutaneous grade II mast cell tumors: 28 dogs (1994–2002) |journal=J Vet Intern Med |volume=20 |issue=4 |pages=933–40 |year=2006 |pmid=16955819 |doi=10.1111/j.1939-1676.2006.tb01808.x }}&lt;/ref&gt; Any mast cell tumor found in the [[gastrointestinal tract]], paw, or on the muzzle has a guarded prognosis.  Previous beliefs that tumors in the groin or [[perineum]] carried a worse prognosis have been discounted.&lt;ref name=Sfiligoi&gt;{{cite journal |vauthors=Sfiligoi G, Rassnick K, Scarlett J, Northrup N, Gieger T |title=Outcome of dogs with mast cell tumors in the inguinal or perineal region versus other cutaneous locations: 124 cases (1990–2001) |journal=J Am Vet Med Assoc |volume=226 |issue=8 |pages=1368–74 |year=2005 |pmid=15844431 |doi=10.2460/javma.2005.226.1368}}&lt;/ref&gt; Tumors that have spread to the lymph nodes or other parts of the body have a poor prognosis. Any dog showing symptoms of mastocytosis or with a grade III tumor has a poor prognosis. Dogs of the Boxer breed have a better than average prognosis because of the relatively benign behavior of their mast cell tumors.&lt;ref name=Morrison_1998/&gt; Multiple tumors that are treated similarly to solitary tumors do not seem to have a worse prognosis.&lt;ref&gt;{{cite journal |vauthors=Mullins M, Dernell W, Withrow S, Ehrhart E, Thamm D, Lana S |title=Evaluation of prognostic factors associated with outcome in dogs with multiple cutaneous mast cell tumors treated with surgery with and without adjuvant treatment: 54 cases (1998–2004) |journal=J Am Vet Med Assoc |volume=228 |issue=1 |pages=91–5 |year=2006 |pmid=16426175 |doi=10.2460/javma.228.1.91|doi-access=free }}&lt;/ref&gt;

Mast cell tumors do not necessarily follow the histological prognosis. Further prognostic information can be provided by AgNOR stain of histological or cytological specimen.&lt;ref&gt;{{cite journal |vauthors=Scase T, Edwards D, Miller J, Henley W, Smith K, Blunden A, Murphy S |title=Canine mast cell tumors: correlation of apoptosis and proliferation markers with prognosis |journal=J Vet Intern Med |volume=20 |issue=1 |pages=151–8 |year=2006 |pmid=16496935 |doi=10.1892/0891-6640(2006)20[151:CMCTCO]2.0.CO;2|hdl=10871/37694 |hdl-access=free }}&lt;/ref&gt; Even then, there is a risk of unpredictable behavior.

==Other animals==
Mast cell tumors are an uncommon occurrence in [[horse]]s. They usually occur as benign, solitary masses on the skin of the head, neck, trunk, and legs. Mineralization of the tumor is common.&lt;ref&gt;{{cite journal |vauthors=Cole R, Chesen A, Pool R, Watkins J |title=Imaging diagnosis—equine mast cell tumor |journal=Vet Radiol Ultrasound |volume=48 |issue=1 |pages=32–4 |year=2007 |pmid=17236357 |doi=10.1111/j.1740-8261.2007.00200.x}}&lt;/ref&gt;  In [[pig]]s and [[cattle]], mast cell tumors are rare. They tend to be solitary and benign in pigs and multiple and malignant in cattle.&lt;ref name=Merck/&gt; Mast cell tumors are found in the skin of cattle most commonly, but these may be metastases from tumors of the [[viscus|viscera]].&lt;ref&gt;{{cite journal |vauthors=Smith B, Phillips L |title=Congenital mastocytomas in a Holstein calf |journal=Can Vet J |volume=42 |issue=8 |pages=635–7 |year=2001 |pmid=11519274 |pmc=1476568}}&lt;/ref&gt; Other sites in cattle include the spleen, muscle, gastrointestinal tract, [[Greater omentum|omentum]], and uterus.&lt;ref&gt;{{cite journal |vauthors=Ames T, O'Leary T |title=Mastocytoma in a cow: a case report |journal=Can J Comp Med |volume=48 |issue=1 |pages=115–7 |year=1984 |pmid=6424914 |pmc=1236018}}&lt;/ref&gt;

===Dogs===
Mast cell tumors mainly occur in older adult dogs, but have been known to occur on rare occasions in puppies. The following breeds are commonly affected by mast cell tumors:
*[[Boxer (dog)|Boxer]]
*[[Staffordshire bull terrier]]
*[[Bulldog]]
*[[Basset hound]]
*[[Weimaraner]]
*[[Boston terrier]]
*[[Great Dane]]
*[[Golden retriever]]
*[[Labrador retriever]]
*[[Beagle]]
*[[German shorthaired pointer]]
*[[Scottish terrier]]&lt;ref name=Morrison_1998&gt;{{cite book|author=Morrison, Wallace B.|title=Cancer in Dogs and Cats|url=https://archive.org/details/cancerindogscats0000morr|url-access=registration|edition=1st|publisher=Williams and Wilkins|year=1998|isbn=0-683-06105-4}}&lt;/ref&gt;
*[[Pug]]
*[[Shar pei]]&lt;ref&gt;{{cite journal |author=Miller D |title=The occurrence of mast cell tumors in young Shar-Peis |journal=J Vet Diagn Invest |volume=7 |pages=360–363 |year=1995 |pmid=7578452 |issue=3 |doi=10.1177/104063879500700311|doi-access=free }}&lt;/ref&gt;
*[[Rhodesian ridgeback]]&lt;ref name=Merck&gt;{{cite web | title = Cutaneous Mast Cell Tumors | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/72231.htm | access-date = 2007-01-27 }}&lt;/ref&gt;

===Cats===
Two types of mast cell tumors have been identified in cats, a mast cell type similar to dogs and a [[histiocyte|histiocytic]] type that appears as subcutaneous nodules and may resolve spontaneously. Young [[Siamese (cat)|Siamese cat]]s are at an increased risk for the histiocytic type,&lt;ref name=pathol/&gt; although the mast cell type is the most common in all cats and is considered to be benign when confined to the skin.&lt;ref name=Merck/&gt;

Mast cell tumors of the skin are usually located on the head or trunk.&lt;ref&gt;{{cite journal |vauthors=Litster A, Sorenmo K |title=Characterisation of the signalment, clinical and survival characteristics of 41 cats with mast cell neoplasia |journal=J Feline Med Surg |volume=8 |issue=3 |pages=177–83 |year=2006 |pmid=16476559 |doi=10.1016/j.jfms.2005.12.005|s2cid=20724869 |doi-access=free |pmc=10832862 }}&lt;/ref&gt; Gastrointestinal and [[spleen|splenic]] involvement is more common in cats than in dogs; 50 percent of cases in dogs primarily involved the spleen or intestines.&lt;ref name=Takahashi&gt;{{cite journal |vauthors=Takahashi T, Kadosawa T, Nagase M, Matsunaga S, Mochizuki M, Nishimura R, Sasaki N |title=Visceral mast cell tumors in dogs: 10 cases (1982–1997) |journal=J Am Vet Med Assoc |volume=216 |issue=2 |pages=222–6 |year=2000 |pmid=10649758 |doi=10.2460/javma.2000.216.222|doi-access=free }}&lt;/ref&gt; Gastrointestinal mast cell tumors are most commonly found in the [[Muscularis mucosae|muscularis layer]] of the [[small intestine]], but can also be found in the [[large intestine]].&lt;ref&gt;{{cite web | title = Gastrointestinal Neoplasia | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/23307.htm | access-date = 2007-01-27 }}&lt;/ref&gt; It is the third most common intestinal tumor in cats, after [[lymphoma in animals|lymphoma]] and [[adenocarcinoma]].&lt;ref&gt;{{cite journal | last = Moriello | first = Karen A. | title = Clinical Snapshot | journal = Compendium on Continuing Education for the Practicing Veterinarian | volume = 29 | issue = 4 | page = 204 | publisher = Veterinary Learning Systems |date=April 2007 }}&lt;/ref&gt;

Diagnosis and treatment are similar to that of the dog. Cases involving difficult to remove or multiple tumors have responded well to [[strontium-90]] [[radiation therapy|radiotherapy]] as an alternative to surgery.&lt;ref&gt;{{cite journal |vauthors=Turrel J, Farrelly J, Page R, McEntee M |title=Evaluation of strontium 90 irradiation in treatment of cutaneous mast cell tumors in cats: 35 cases (1992–2002) |journal=J Am Vet Med Assoc |volume=228 |issue=6 |pages=898–901 |year=2006 |pmid=16536702 |doi=10.2460/javma.228.6.898|doi-access=free }}&lt;/ref&gt; The prognosis for solitary skin tumors is good, but guarded for tumors in other organs. Histological grading of tumors has little bearing on prognosis.&lt;ref&gt;{{cite journal |vauthors=Molander-McCrary H, Henry C, Potter K, Tyler J, Buss M |title=Cutaneous mast cell tumors in cats: 32 cases (1991–1994) |journal=J Am Anim Hosp Assoc |volume=34 |issue=4 |pages=281–4 |year=1998 |pmid=9657159 |doi=10.5326/15473317-34-4-281}}&lt;/ref&gt;

==References==
{{Reflist}}

== External links ==
{{Medical resources
|   DiseasesDB     = 34450 
|   ICD10          = {{ICD10|C|96|2|c|81}}, {{ICD10|D|47|0|d|37}} 
|   ICD9           = {{ICD9|238.5}} 
|   ICDO           = M9740/1 
|   OMIM           = 
|   MedlinePlus    = 
|   eMedicineSubj  = derm 
|   eMedicineTopic = 258 
|   MeshID         = D034801 
}}
*[http://www.veterinarypartner.com/Content.plx?P=A&amp;S=0&amp;C=0&amp;A=1600 ''Mast Cell Tumors'' from The Pet Health Library]
*[http://www.petcancercenter.org/Cancer_Types_mast_cell_dog.html ''Mast Cell Tumors in Dogs'' from Pet Cancer Center]
*[http://www.petcancercenter.org/Cancer_Types_mast_cell_cat.html ''Mast Cell Tumors in Cats'' from Pet Cancer Center]

{{Myeloid malignancy|us=y}}
{{Soft tissue tumors and sarcomas}}

[[Category:Dog diseases]]
[[Category:Cat diseases]]
[[Category:Horse diseases]]
[[Category:Swine diseases]]
[[Category:Bovine diseases]]