Vlaams Diergeneeskundig Tijdschrift, 2008, 77 Theme: Equine sarcoids 2 Equine sarcoids - part 1: clinical presentation and epidemiology Equine sarcoïden – deel 1: klinisch voorkomen en epidemiologie L. Bogaert, A. Martens, P. Depoorter, F. Gasthuys Department of Surgery and Anesthesiology of Domestic Animals, Faculty of Veterinary Medicine, Ghent University, Salis- burylaan 133, B-9820 Merelbeke, Belgium [email protected] ABSTRACT Equine sarcoids are the most common skin tumors in horses and other equids. In their pathogenesis, the bovine papillomavirus (BPV) plays a major role. Many clinical manifestations have been described, rang- ing from small single lesions to multiple aggressively growing masses. Histopathologically, it is considered as a biphasic tumor with epidermal hyperplasia and subepidermal proliferation of transformed fibrob- lasts. The diagnosis can be made clinically, histopathologically and/or by detection of BPV DNA. Sarcoids can appear on any part of the body, but they are mostly localized on the ventral abdomen, the paragenital region, head and limbs. Sarcoids occur independent of breed, coat color, sex or age, but they develop more commonly in young adults and certain families and breeds are more vulnerable than others. Transmission of BPV is supposed to happen from cattle to horse or from horse to horse, possibly via insects. SAMENVATTING Equine sarcoïden zijn de meest voorkomende tumoren bij paarden en andere paardachtigen. Het boviene papillomavirus (BPV) speelt een belangrijke rol in de pathogenese. Verschillende klinische vormen worden be- schreven gaande van kleine enkelvoudige laesies tot multipele agressief groeiende gezwellen. Histopathologisch worden sarcoïden beschouwd als bifasische tumoren met epidermale hyperplasie en subepidermale proliferatie van getransformeerde fibroblasten. De diagnose wordt gesteld aan de hand van een klinisch onderzoek, histopa- thologie en/of de detectie van BPV DNA. Sarcoïden kunnen op het hele lichaam voorkomen, maar meestal zijn ze terug te vinden onderaan de buik, in de paragenitale regio, op het hoofd en op de ledematen. Sarcoïden komen wereldwijd voor onafhankelijk van het ras, de haarkleur, het geslacht of de leeftijd maar ontstaan toch voorname- lijk bij jong volwassen dieren. Bepaalde lijnen en rassen zijn eveneens meer gevoelig dan andere. De transmissie van BPV gebeurt vermoedelijk zowel van rund naar paard als tussen paarden onderling, eventueel via insecten. INTRODUCTION tatic dissemination does not occur (Pascoe and Knot- tenbelt, 1999). The clinical presentation of an equine Equine sarcoids are the most common skin tumors sarcoid can vary a lot between different individuals in horses and other equids like donkeys, mules and and even within the same individual. The number of zebras (Jackson, 1936; Ragland, 1970; Lazary et al., tumors per horse varies from one single sarcoid over 1985; Nel et al., 2006). They were described for the a few to more than 100 lesions (Pascoe and Knotten- first time by Jackson (1936), who considered the tu- belt, 1999). A sarcoid can remain stable for years or it mors as sarcoma-like mixed (fibro-epithelial) tumors. can show a rapid and aggressive growth with infiltra- Equine sarcoids are observed worldwide, indepen- tion of surrounding skin (Ragland, 1970; Marti et al., dent of breed, coat color, sex or age (Ragland, 1970; 1993). The reason for these large differences in clini- Tarwid et al., 1985). Nevertheless, certain breeds and cal presentation is presently not known. The infiltra- families are more vulnerable than others (Ragland et tive behavior together with the infectious etiology is al., 1966; Brostrom et al., 1988; Lazary, 1988; Ger- responsible for the frequent recurrences after treat- ber, 1989; Marti et al., 1993) and sarcoids occur most ment. Sarcoids themselves are never lethal, but fai- commonly in young adults, between 3 and 6 years lure to treat them and the functional impairment they (Marti et al., 1993; Torrontegui and Reid, 1994). cause may result in euthanasia or slaughtering. The Clinically and pathologically, sarcoids present most economic repercussion can be great: besides the cos- of the features of a true neoplasm. The predominant metic aspect, the normal use of the horse can be hin- cell type is a malignant/transformed fibroblast. Sar- dered, especially when tumors are located at the le- coids generally have a high capacity for local tissue vel of the girth and bridle, distal limbs, corner of the invasion into the dermis and subcutis but true metas- mouth and eyelids. Moreover a genetic component 3 Vlaams Diergeneeskundig Tijdschrift, 2008, 77 has a role in the development of the disease, dimi- nign type can evolve rapidly towards a more aggres- nishing the breeding value of affected animals (La- sive type, either spontaneously or following injury zary et al., 1985; Meredith et al., 1986; Gerber et al., such as biopsy or an erroneous treatment. Common 1988). Diseased horses are therefore difficult to sell differential diagnoses are dermatophytosis, chronic (Gerber, 1989). skin rubbing, alopecia areata and vitiligo (Knotten- In the pathogenesis, the bovine papillomavirus (BPV) belt et al., 1995). plays a major role. Papillomaviruses are normally Fibroblastic sarcoids (Figure 4) are large fibrous strictly species-specific, but equine sarcoids result masses with an ulcerated surface. This is the most ag- from a natural cross-species infection. Although no gressive sarcoid type and can evolve from any other intact viral particles have been demonstrated in sar- type after accidental or iatrogenic manipulation, in- coids so far, DNA, RNA and proteins of the virus cluding biopsy (Knottenbelt et al., 1995; Foy et al., can be found (Amtmann et al., 1980; Trenfieldet al., 2002). In these cases it is observed that the original 1985; Otten et al., 1993; Teifke et al., 1994; Nasir tumor starts to grow very quickly and begins to ul- and Reid, 1999; Carr et al., 2001b). Moreover, many cerate. Skin wounds, especially at the distal limbs, similarities can be observed between equine sarcoids are also at risk for development of fibroblastic sar- and papillomatosis in other species: fast growth, ten- coids. Both dehiscence of the suture line after surgery dency for multiplicity and spreading by contact over without an apparent reason as well as the presence of different parts of the body (Jackson, 1936). Epizoo- a slow healing hypergranulating wound can be sug- tics have been described in closed herds of horses and gestive of sarcoid development (Pascoe and Knotten- zebras, pointing to an infectious agent (Ragland et belt, 1999). Fibroblastic sarcoids are liable to trau- al., 1966; Nel et al., 2006). ma, haemorrhage and local infection with bacteria or maggots. Fibroblastic sarcoids can be sessile with CLINICAL PRESENTATION OF EQUINE SAR- an invasive character or pedunculated with a small COIDS base. Differential diagnoses are exuberant granula- tion tissue, botryomycosis, squamous cell carcinoma Clinical types and habronemiasis in warmer climates (Knottenbelt et al., 1995). Many clinical manifestations of equine sarcoids Mixed sarcoids (Figure 5) are a combination of are known. They can be single or multiple, small to two or more of the above mentioned types. They can very large, stable or aggressively growing. At cross- represent a progressive or transient state between the section sarcoids appear as dermal thickening with verrucous/occult types and the fibroblastic/nodular a pale yellow color and a firm texture due to fibro- types (Pascoe and Knottenbelt, 1999). blastic proliferation and a small number of capilla- Malevolent sarcoids are very rare and have been ries within the tumor (Foy et al., 2002). The epider- described only by one group (Knottenbelt et al., mis varies from thick, rough and hyperkeratotic to 1995). These tumors infiltrate in lymphatic vessels thinned or ulcerated. A classification based on mor- resulting in multiple nodular or fibroblastic masses phological features has been proposed by Pascoe and along these vessels. Local lymph nodes might also be Knottenbelt (1999) and will be followed throughout involved. This type of sarcoid usually evolves from this paper. any of the other types following repeated injury, al- Verrucous sarcoids (Figure 1) have a typical wart-­­ though spontaneous transformation is also possible. like appearance with a rough, thickened, scabby sur- In our clinic, sarcoids infiltrating the underlying face above the fibroblastic part of the tumor (Knotten- muscles have occasionally been observed. These sar- belt et al., 1995). They can appear as small exophytic coids can arise spontaneously or following failure of growing masses or as flat, often extended, scaly are- treatment resulting in deterioration of the tumor. as of skin with multiple smaller wart-like lesions on This classification into different types is also re- the surface. Common differential diagnoses for this flecting the clinical behavior of the tumors: occult ty- sarcoid type are warts (induced by equine papilloma- pes are the most stable tumors, nodular and verrucous virus), aural plaque, chronic sweet itch and chronic sarcoids display a moderate growth, fibroblastic sar- blistering (Pascoe and Knottenbelt, 1999). coids are often fast growing and malevolent and in- Nodular sarcoids (Figure 2) are subcutaneous, filtrating sarcoids, although rarely seen, are the most easily moveable nodules, often but not always sphe- aggressive sarcoid types. rical, covered by intact, apparently normal skin (Foy