Histiocytoma (dog)

A histiocytoma in the dog is a benign tumor. It is an abnormal growth in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. A similar disease in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. [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] Dog breeds that may be more at risk for this tumor include Bulldogs, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. They also rarely occur in goats and cattle. [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 ]

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 cells are dendritic cells found in the skin and function by internalizing antigens (foreign particles) and presenting them to T cells. They arise from monocytes. [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] 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 hemophagocytic lymphohistiocytosis in humans)
*Malignant diseases of Langerhans dells
**Malignant histiocytosis - a condition found in Bernese Mountain Dogs
**Diffuse histiocytic sarcoma
**Localized histiocytic sarcoma
*Malignant diseases of macrophages
**Histiocytic lymphoma

Tumor biology

A histiocytoma originates from epidermal Langerhans cells of antigen-presenting cell lineage. [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] 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 cytokines (such as Interferon-gamma) and recruitment of antitumour effector cells. [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]

ymptoms

Most commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump,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] although Shar Peis may be predisposed to multiple histiocytomas.cite journal | last = Cronin | first = Kim | title = Deciphering the histiocytic code | journal = DVM | pages = 1S–8S | publisher = Advanstar Communications | date = Dec. 2006 ] They are most commonly found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter. [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 ] Ulceration of the mass is common. Diagnosis is made through cytology of the mass. Cytology reveals cells with clear to lightly basophilic cytoplasm and round or indented nuclei with fine chromatin and indistinct nucleoli. [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 ]

Treatment

Most histiocytomas will regress within two or three months. 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

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]