Histiocytoma (dog)
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2008-05-28T19:53:56Z
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[[Image:Histiocytoma.JPG|thumb|A histiocytoma on the ear of a dog]]
[[Image:Canine histiocytoma.jpg|thumb|Canine Cutaneous Histiocytoma on a young boxer dog]]
A '''histiocytoma''' in the [[dog]] is a benign tumor. It is an abnormal growth in the skin of [[histiocyte]]s ([[histiocytosis]]), a cell that is part of the [[immune system]]. A similar disease in humans, [[Hashimoto-Pritzker disease]], is also a [[Langerhans cell histiocytosis]].<ref>{{cite journal |author=Marchal T, Saint-André I, Magnol J, Dezutter-Dambuyant C, Schmitt D |title=[Dendritic cells in dogs and cats: models of study in human pathology] |journal=Pathol. Biol. |volume=43 |issue=10 |pages=910–20 |year=1995 |pmid=8786898}}</ref> Dog breeds that may be more at risk for this tumor include [[Bulldog]]s, [[Scottish Terrier]]s, [[Greyhound]]s, [[Boxer (dog)|Boxer]]s, and [[Boston Terrier]]s. They also rarely occur in [[goat]]s and [[cattle]].<ref>{{cite web | title = Tumors with Histiocytic Differentiation | work = The Merck Veterinary Manual | date = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/72232.htm | accessdate = 2007-04-29 }}</ref>
==Histiocytic disorders==
A histiocyte is a differentiated tissue cell that has its origin in the [[bone marrow]]. The source for histiocytes is the [[monocyte]]/[[macrophage]] line. Monocytes (found in the blood) and macrophages (found in tissue) are responsible for [[phagocytosis]] (ingestion) of foreign material in the body. [[Langerhans cell]]s are [[dendritic cell]]s found in the skin and function by internalizing [[antigen]]s (foreign particles) and presenting them to [[T cell]]s. They arise from monocytes.<ref>{{cite journal |author=Ginhoux F, Tacke F, Angeli V, Bogunovic M, Loubeau M, Dai XM, Stanley ER, Randolph GJ, Merad M |title=Langerhans cells arise from monocytes ''in vivo'' |journal=Nat. Immunol. |volume=7 |issue=3 |pages=265–73 |year=2006 |pmid=16444257 |doi=10.1038/ni1307}}</ref> Histiocytic disorders refer to diseases that are caused by abnormal behavior of these cells. They include the following:
*Reactive diseases of Langerhans cells
**Histiocytomas
**Cutaneous histiocytosis
**Systemic histiocytosis
*Reactive diseases of macrophages
**[[Hemophagocytic syndrome]] - a condition where macrophages phagocytose [[myeloid]] and [[erythroid]] precursors (similar to [[HLH (Hemophagocytic lymphohistiocytosis)|hemophagocytic lymphohistiocytosis]] in humans)
*Malignant diseases of Langerhans dells
**[[Malignant histiocytosis]] - a condition found in [[Bernese Mountain Dog]]s
**[[Diffuse histiocytic sarcoma]]
**Localized histiocytic sarcoma
*Malignant diseases of macrophages
**[[Histiocytic lymphoma]]
==Tumor biology==
[[Image:Canine histiocytoma cytology.JPG|thumb|Canine histiocytoma cytology]]
A histiocytoma originates from epidermal Langerhans cells of [[antigen-presenting cell]] lineage.<ref>{{cite journal |author=Moore P, Schrenzel M, Affolter V, Olivry T, Naydan D |title=Canine cutaneous histiocytoma is an epidermotropic Langerhans cell histiocytosis that expresses CD1 and specific beta 2-integrin molecules |journal=Am. J. Pathol. |volume=148 |issue=5 |pages=1699–708 |year=1996 |pmid=8623937}}</ref> Spontaneous regression is common in these tumors, and it is mediated by infiltration of [[CD8]]-expressing T cells followed by expression of Type 1 [[T helper cell]] [[cytokine]]s (such as [[Interferon-gamma]]) and recruitment of antitumour [[effector cell]]s.<ref>{{cite journal |author=Kaim U, Moritz A, Failing K, Baumgärtner W |title=The regression of a canine Langerhans cell tumour is associated with increased expression of IL-2, TNF-alpha, IFN-gamma and iNOS mRNA |journal=Immunology |volume=118 |issue=4 |pages=472–82 |year=2006 |pmid=16764690}}</ref>
==Symptoms==
Most commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump,<ref name=Morrison_1998>{{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}}</ref> although [[Shar Pei]]s may be predisposed to multiple histiocytomas.<ref name=DVM>{{cite journal | last = Cronin | first = Kim | title = Deciphering the histiocytic code | journal = DVM | pages = 1S–8S | publisher = Advanstar Communications | date = Dec. 2006 }}</ref> They are most commonly found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter.<ref>{{cite web | last = Affolter | first = Verena K. | title = Histiocytic Proliferative Diseases in Dogs and Cats | work = Proceedings of the 29th World Congress of the World Small Animal Veterinary Association | date = 2004 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&PID=8600&O=Generic | accessdate = 2007-04-29 }}</ref> Ulceration of the mass is common. Diagnosis is made through [[cytopathology|cytology]] of the mass. Cytology reveals cells with clear to lightly [[basophilic]] [[cytoplasm]] and round or indented [[cell nucleus|nuclei]] with fine [[chromatin]] and indistinct [[nucleolus|nucleoli]].<ref>{{cite web | last = Raskin | first = R.E. | coauthors = DeNicola, D. | title = Cytology of Neoplasia | work = Proceedings of the North American Veterinary Conference | date = 2006 | url = http://www.ivis.org/proceedings/NAVC/2006/SAE/105.asp?LA=1 | accessdate = 2007-04-29 }}</ref>
==Treatment==
Most histiocytomas will regress within two or three months.<ref name=Morrison_1998/> Surgical removal may be necessary if the tumor does not regress or if it is growing rapidly to a large size. Histiocytomas can also be treated with an intralesional injection of a [[corticosteroid]], but this is not always successful.
==References==
{{Reflist}}
==External links==
*[http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=1676 ''Histiocytoma'' from The Pet Health Library]
*[http://www.petcancercenter.org/Cancer_Types_soft_tissue_histiocytic_sarcoma.html ''Histiocytoma and Histiocytic Sarcoma in Cats and Dogs'' from Pet Cancer Center]
[[Category:Dog diseases]]