Skin cancer, or neoplasia, is the most common type of cancer diagnosed in horse , accounting for 45 to 80% of all cancers diagnosed. Sarcoid is the most common type of skin neoplasm and is the most common type of cancer in horses as a whole. Squamous cell carcinoma is the second most common skin cancer, followed by melanoma. Squamous cell carcinoma and melanoma usually occur in horses larger than 9 years, while sarcoids generally attack horses aged 3 to 6 years. Surgical biopsy is the method of choice for the diagnosis of most horse skin cancers, but is contraindicated for sarcoid cases. The prognosis and effectiveness of treatment vary by type of cancer, the extent of local tissue damage, evidence of spread to other organs (metastasis) and the location of the tumor. Not all cancers metastasize and some can be cured or reduced by surgical removal of cancer tissue or through the use of chemotherapy drugs.
Video Skin cancer in horses
Sarcoids
Sarcoids accounts for 39.9% of all horse cancers and is the most common cancer diagnosed in horses. There is no predilection of breeding to develop sarcoid and they can occur at any age, with horses aged three to six years being the most common age group and men being a little more susceptible to developing the disease. Sarcoids are also more common in certain family lines, suggesting that there may be inherited components. Several studies have found an association between the presence of papillomavirus-1 Bovine and 2 and associated viral growth proteins in skin cells with sarcoid formation, but the exact mechanisms that control or induce epidermal proliferation are unknown. However, high viral load in cells is strongly correlated with more severe clinical signs and aggressive lesions.
Clinical signs
The appearance and number of sarcoids may vary, with some horses having single or multiple lesions, usually in the head, legs, ventrum and genitals or around the wound. The pattern of distribution suggests that flies are an important factor in the formation of sarcoid. Sarcoid can resemble warts (verukosa form), small nodules (nodular shape), hairless oval or scaly plaques (occult forms) or very rarely, large mass of ulceration (fibroblastic form). Occult forms usually appear on the skin around the mouth, eyes or neck, while the nodular and necular sarcoids are common in the groin, penis or facial sheath. Fibroblastic sarcoid has predilection for legs, groin, eyelids and previous injury sites. Some forms can also be present on individual horses (mixed shapes). Histologically, sarcoid consists of fibroblasts (cells that produce collagen) that attack and multiply in the dermis and sometimes subcutaneous tissue but not easily metastasize to other organs. Surgical biopsy can definitively diagnose sarcoids, but there is a significant risk of making the sarcoid worse. Therefore, the diagnosis is based only on clinical signs, fine needle aspiration or complete excision biopsy is a safer option.
Treatment
While sarcoid can spontaneously withdraw without treatment in some cases, the course and duration of the disease are highly unpredictable and should be considered on a case-by-case basis considering the cost of care and the severity of clinical signs. Surgical removal alone is ineffective, with recurrences occurring in 50 to 64% of cases, but removal is often performed in conjunction with other treatments. Topical treatments with products containing blood roots extract (from Sanguinaria canadensis plants) for 7 to 10 days have been reported to be effective in removing small sarcoids, but the caustic nature of salap can cause pain and sarcoid should be in areas where bandages can be applied. Frozen sarcoid with liquid nitrogen (cryotherapy) is another affordable method, but it can cause scarring or depigmentation. Topical anti-metabolite 5-fluorouracil applications also get good results, but it usually takes 30 to 90 days for repeated applications before any effect can be realized. Small sarcoid injections (usually around the eyes) with cisplatin chemotherapy agents and BCG immunomodulators also achieve some success. In one trial, BCG was 69% effective in treating small and nodular fibroblastic sarcoids around the eyes when repeatedly injected into the lesion and injection with cisplatin was 33% effective overall (mostly on horses with nodular sarcoids). However, BCG treatment carries the risk of allergic reactions in some horses and cisplatin has a tendency to leak out of the sarcoid during repeated doses. External beam radiation can also be used on small sarcoids, but it is often impractical. Cisplatin electrochemotherapy, when used with or without prior surgery to remove sarcoid, had a non-recurrent rate after four years of 97.9% in one retrospective study. Cisplatin electrochemotherapy (the application of an electric field for sarcoids after cisplatin injection, with horses under general anesthesia) There is a possibility of sarcoid recurrence for all modalities even after seemingly successful treatment. While sarcoid is not fatal, large aggressive tumors that damage surrounding tissue can cause discomfort and loss of function and resistance to treatment, making euthanasia justifiable in some cases. Sarcoid is probably the most common skin-related reason for euthanasia.
Maps Skin cancer in horses
Squamous cell carcinoma
Squamous cell carcinoma (SCC) is the most common eye cancer, the periorbital region and penis, and this is the second most common cancer overall in horses, accounting for 12 to 20% of all cancers diagnosed. While SCC has been reported in horses aged 1 to 29 years, most cases occur in horses aged 8 to 15 years, making it the most commonly reported neoplasm in older horses. Carcinoma is a tumor derived from epithelial cells and SCC results from the transformation and proliferation of squames, epidermal skin cells that become keratin. Squamous cell carcinomas are often solitary, slow-growing tumors that cause extensive local tissue damage. They can metastasize to other organs, with levels reported as high as 18.6%, especially to lymph nodes and lungs.
Clinical signs and predisposing factors
Tumors associated with squamous cell carcinoma (SCC) can appear anywhere in the body, but they are most commonly located in non-pigmented skin near the mucocutaneous intersections (where the skin meets the mucous membranes) as on the eyelids, around the nostrils, the lips , vulva, foreskin, penis or anus. Tumors are raised, fleshy, often ulcerated or infected and may have irregular surfaces. Rarely, primary SCC develops in the esophagus, the stomach (the non-gland), the nasal and sinus passages, the hard palate, the gums, the gutural pouch and the lungs. Eyelids are the most common sites, accounting for 40-50% of cases, followed by men (25-10% of cases) and women (10% of cases) of genitals. Horses with light-pigmented skin, such as those having gray coat or white faces, are particularly vulnerable to developing SCC, and some offspring, such as Clydesdales, may have a genetic predisposition. Exposure to light colored skin against UV rays is often referred to as a predisposing factor, but lesions can occur in dark skin and in areas not normally exposed to sunlight, such as around the anus. Smegma buildup ("beans" in horseracing terms) on the penis is also associated with SCC and is considered a carcinogen through penile irritation. Pony geldings and working horses are more prone to develop SCC in the penis, because washing the penis is less common when compared to horses. Equine papillomavirus-2 has also been found in SCC penis, but has not been determined to cause SCC.
SCC care and prevention
Before the treatment of squamous cell carcinoma (SCC) begins, evidence of metastasis should be determined by either palpation and lymph aspiration around the mass or, in smaller horses, chest radiography. Small tumors found early in the disease process (most commonly on the eyelids) can be treated with cisplatin or radiation with favorable results. For more advanced cases, surgical removal of the eye (enukleasi), mass amputation or penis can be curative as long as all cancer cells are removed (wide margins obtained) and no metastasis. However, young horses (usually geldings of less than 8 years) who have a hard texture or "wood" for SCC on glans penis have a very poor prognosis for treatment and recovery.
Regular washing of the penis and foreskin in men and clearing clitoral fossa (groove around the clitoris) on the horse is recommended to eliminate smegma buildup, which also provides an opportunity for examination for suspicious growth of the penis or the vulva.
Melanoma
Equine melanoma results from abnormal proliferation and accumulation of melanocytes, pigmented cells in the dermis. Gray horses over 6 years old are particularly vulnerable to developing melanoma. The prevalence of melanoma in gray horses over 15 years has been estimated at 80%. A survey of Camargue-type horses found an overall population prevalence of 31.4%, with prevalence increasing to 67% in horses over the age of 15 years. Up to 66% melanoma in a gray horse is benign, but melanotic tumors in horses with dark-coat hair may be more aggressive and more often malignant. One retrospective study of cases sent to referral hospitals reported 14% of the prevalence of metastatic melanoma in the study population. However, the actual prevalence of metastatic melanoma may be lower due to the rare submission of melanotic tumors for diagnosis. Common sites for metastasis include lymph nodes, liver, spleen, lung, skeletal muscle, blood vessels and parotid salivary glands.
Clinical signs
The most common sites for melanosis tumors are at the bottom of the tail near the base, in the foreskin, around the mouth or in the skin above the parotid gland (near the ear). The tumor will initially begin as a single, small-bred area that can multiply or merge into a multi-lobed mass (a process called melanomatosis) over time. Horses under the age of 2 years can be born with or acquire a melanotic benign tumor (called melanocytomas), but these tumors are often located in the legs or stems, not under the tail as in older animals.
Melanoma Treatment
Treatment of small melanomas is often unnecessary, but large tumors can cause discomfort and usually surgery removed. Cisplatin and cryotherapy can be used to treat small tumors less than 3 cm, but tumors can recur. Cimetidine, a histamine stimulator, can cause tumors to regress in some horses, but it can take up to 3 months to produce results and some treatments may be needed throughout the life of the horse. There are several viable treatment options for horses with metastatic melanoma. However, gene therapy injections utilizing DNA plasmid interleukin-12 and 18-encoding have shown promise in slowing tumor progression in patients with metastatic melanoma.
Other types of skin cancer
Lymphoma
Source of the article : Wikipedia
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