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Basics ⬇

Outline

BASICS

Definition!!navigator!!

A neoplasm of fibroblastic origin that generally has a low metastatic potential, yet is often locally aggressive. There are several clinical forms ranging from areas of alopecia and altered, flaky skin to more pronounced nodular lesions with or without overlying skin involvement or fleshy, proliferative masses with ulceration.

Pathophysiology!!navigator!!

  • Etiopathogenesis is unknown, but BPV has been implicated as an inciting agent. Intradermal inoculation with extract from bovine skin tumors caused by BPV has caused lesions in horses resembling equine sarcoid
  • Additionally, genetic susceptibility may exist with equine sarcoid. Horses that express certain MHC-encoded ELAs (MHC-I ELA W3 and B1 and MHC-II ELA W13 and A5) have increased incidence and higher recurrence rates after surgery. Flies have been implicated as vectors for transfer of infectious agents or sarcoid cells between animals

Systems Affected!!navigator!!

  • Eyelids and periocular skin
  • Equine sarcoid can affect any cutaneous area, but approximately 32% of the tumors are located on the head and neck. As many as 14% of all the equine sarcoids are periocular

Genetics!!navigator!!

  • No proven genetic basis, but genes in or near MHC have been implicated
  • There has also been demonstrated a correlation between the development of sarcoids and heterozygosity for the equine severe combined immunodeficiency allele

Incidence/Prevalence!!navigator!!

Sarcoids are the most commonly reported equine tumor overall and the second most common periocular tumor of the horse.

Geographic Distribution!!navigator!!

No reported geographic distribution.

Signalment!!navigator!!

Species

Horses, donkeys, and mules.

Breed Predilections

Nearly all breeds have been reported to have sarcoids. However, Quarter Horses, Appaloosas, Arabians, and Thoroughbreds are reported to have the highest risk, while Standardbreds and Lipizzaners have the lowest.

Mean Age and Range

Mean age of affected animals is between 3 and 7 years, with a range of 1 to >15 years.

Predominant Sex

No proven sex predilection.

Signs!!navigator!!

Historical Findings

  • Single or multiple areas of dermal thickening or nodules in the eyelids or periocular region
  • Lesions may be ulcerated, and those affecting the eyelid margins or canthi may cause tearing, squinting, or ocular discharge
  • Ocular irritation often occurs because of either disruption of eyelid function or direct rubbing on the globe
  • Growth rate and biologic behavior are highly variable

Physical Examination Findings

  • Nonspecific findings may include serous to mucopurulent ocular discharge, blepharospasm, and conjunctival hyperemia
  • Solitary or multiple areas of linear or focal dermal thickening in the eyelids or periocular skin can be found. Lesions may also appear as nodules or pedunculated masses. Cutaneous ulceration and infection may be present

Causes!!navigator!!

  • Viral etiologies have been suggested
  • A predisposition associated with genes on or near the MHC has also been suggested

Risk Factors!!navigator!!

  • Possible breed predilections, possible genetic risk factors
  • Epizootics in herds suggest an infectious risk, possibly associated with fly vectors

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Diagnosis depends on an index of clinical suspicion and histopathology
  • Differentials include granulation tissue or scarring; granulomas caused by habronemiasis, onchocerciasis, or foreign body reactions; fungal dermatitis; dermatophilus; and other tumors such as squamous cell carcinoma, papilloma, fibroma, and fibrosarcoma

CBC/Biochemistry/Urinalysis!!navigator!!

Results usually normal.

Imaging!!navigator!!

Skull radiographs may be required if orbital or other bony involvement is suspected.

Pathologic Findings!!navigator!!

Gross

  • Several morphologic types of sarcoid have been described
  • Occult lesions are those with alopecia, altered hair, and small miliary nodules or plaques
  • The verrucous (“warty”) sarcoid is usually <6 cm in diameter, often with cauliflower edges and extensive flakiness of the skin with or without some ulceration
  • Nodular lesions may or may not have epidermal involvement (type A versus type B)
  • Fibroblastic lesions may be sessile and pedunculated. They often have a fleshy, ulcerated appearance
  • The mixed sarcoid is a combination of the previous types
  • Malignant sarcoids are unusual

Histologic

  • Moderate to high density of fusiform or spindle-shaped fibroblastic cells that form whorls, interlacing bundles, and haphazard arrays (fibroblastic proliferation)
  • Cytoplasmic boundaries are ill defined, and the amount of collagen varies considerably
  • The mitotic rate is low
  • In many sarcoids, fibroblastic cells are oriented perpendicularly to the overlying epithelial basement membrane
  • A histopathologic diagnosis requires sampling the overlying skin as well as the deeper lesion of interest for nodular forms

Treatment ⬆ ⬇

Outline

TREATMENT

Inpatient Versus Outpatient!!navigator!!

  • Small superficial lesions may be removed standing with sedation and local anesthesia
  • Larger more invasive lesions, or lesions involving the eyelid margins or canthi, may require hospitalization for surgery
  • Alternatively, lesions may be treated under sedation and local anesthesia using intralesional chemotherapy, immunotherapy, or photodynamic therapy

Activity!!navigator!!

  • Restrict during the immediate postoperative period
  • The eye should be protected from self-trauma with a soft- or hard-cup hood

Client Education!!navigator!!

  • If intralesional chemotherapy is used, the client should be instructed to wear gloves when handling the periocular region for several days post injection
  • The client should be made aware of clinical signs suggesting tumor recurrence
  • Small insults to a sarcoid lesion, such as self-trauma from rubbing or even biopsy for confirmation of the diagnosis, may result in rapid progression, expansion, or transformation of the sarcoid. A plan for therapy to quickly follow biopsy should be made

Surgical Considerations!!navigator!!

  • Complete surgical excision of periocular sarcoid can be difficult or impossible, and recurrence rates of 50–64% have been reported with surgical excision alone. When surgical excision is combined with adjunctive therapy, success rates range from 65% to 95%. Various adjunctive therapies include cryotherapy, hyperthermia, CO2 laser photoablation, topical chemotherapy, radiotherapy, and intralesional chemotherapy, immunotherapy, and photodynamic therapy. Reconstructive eyelid surgery may also be necessary following excision of periocular sarcoids
  • Intralesional BCG injections require multiple injections (every 1–2 weeks) with success rates ranging from 69% to 100%. Intralesional chemotherapy with either cisplatin or 5-FU can produce cures in up to 80% of cases. Cryotherapy (–20° to –40°C, triple freeze–thaw cycle) induces cryonecrosis of sarcoid cells with success rates of up to 75%. Radiofrequency hyperthermia has been reported to induce tumor regression (50°C for 30 s, 2 MHz). Multiple treatments may be necessary to prevent recurrence. 1 study reported an 81% success rate using CO2 laser photoablation. Advantages included a clean, dry surgical site and a lack of postoperative pain and swelling. Radiation therapy has the highest success rates, in many cases approaching 100%, depending upon the source of radiation used. Unfortunately, radiation therapy, while it is the gold standard, is a difficult modality to access due to hazards to involved personnel

Medications ⬆ ⬇

MEDICATIONS

Drug(s) and Fluids

Topical and Intralesional Immunotherapy/Chemotherapy

  • Daily applications of topical 5-FU (1% TID) have been used with inconsistent results
  • Herbal pastes of blood root extracts can be used topically in some sarcoids (XXTerra; Larson Labs, Fort Collins, CO)
  • Intralesional chemotherapeutics including 5-FU and cisplatin have been used with some success. Intralesional cisplatin or carboplatin in purified medical grade sesame oil is administered in 4 or more sessions at 2 week intervals using 1 mg/cm3 of tumor
  • Immunotherapy includes autogenous vaccines or immunomodulators. Intralesional injections of BPV vaccine have been successful in horses with sarcoids, but systemic side effects have been severe in a few horses. Immunomodulation using BCG-attenuated Mycobacterium bovis cell wall in oil, however, has produced remission rates approaching 100%—1 mL of BCG/cm2 of tumor surface area is injected into the lesion. Therapy is repeated every 2–4 weeks for up to 9 injections. Anaphylaxis may occur and can be minimized with pretreatment using flunixin meglumine (1.1 mg/kg IV) and corticosteroids or diphenhydramine

Supportive Therapy

Topical and systemic broad-spectrum antibiotics may be required to prevent infection following surgical and adjunctive therapy of periocular sarcoid. Systemic NSAIDs may be indicated following surgical excision or adjunctive therapy. Flunixin meglumine (1.1 mg/kg) provides analgesic and anti-inflammatory effects, and it may reduce the severity of anaphylaxis associated with intralesional immunotherapy.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Patients should be observed for signs of anaphylaxis immediately post injection when immunomodulating agents are used
  • Long-term follow-up includes monitoring for tumor recurrence or failure of tumor regression

Prevention/Avoidance!!navigator!!

Fly control may reduce the incidence of sarcoid in herds with affected animals.

Possible Complications!!navigator!!

  • Tumor progression may lead to eyelid deformation, possibly resulting in secondary keratitis and conjunctivitis. Tissue necrosis causing similar ocular problems may occur with blood root extracts and other topical and intralesional therapies
  • Ulceration of lesions may lead to secondary bacterial or fungal infections and possible septicemia. With ulcerated lesions, myiasis may be a problem

Expected Course and Prognosis!!navigator!!

  • Prognosis for life is generally good for animals with single sarcoids, as these tumors do not metastasize
  • In animals with numerous sarcoids, seen rarely in the USA and more commonly seen in the UK, prognosis for life is poor
  • Factors affecting prognosis include tumor size, location, degree of local invasiveness, and response to previous therapy
  • Recurrence rates following therapy depend on the therapeutic modalities used

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Zoonotic Potential!!navigator!!

No proven zoonotic potential, but multiple occurrences in some herds suggest that this is possible. If so, fly vectors may be involved, possibly necessitating fly control.

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Abbreviations!!navigator!!

  • 5-FU = 5-fluorouracil
  • BCG = bacillus Calmette-Guérin
  • BPV = bovine papillomavirus
  • ELA = equine leukocyte antigen
  • MHC = major histocompatibility complex
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Brooks DE. Ophthalmology for the Equine Practitioner, 2e. Jackson, WY: Teton NewMedia, 2008.

Brooks DE, Matthews AG. Equine ophthalmology. In: Gelatt KN, ed. Veterinary Ophthalmology, 4e. Ames, IA: Blackwell, 2007:1165–1274.

Gilger BC, ed. Equine Ophthalmology, 3e. Ames, IA: Wiley Blackwell, 2017.

Author(s) ⬆

Author: Caryn E. Plummer

Consulting Editor: Caryn E. Plummer