most common neoplasm affecting horse. Benign but can be locally aggressive. Fibroma-type structures. Aetiology is unknown but BPV or similar viral cause suspected. Some evidence that they can be spread by flies.

Clinical features: Distribution – can grow anywhere but common on head, groin, prepuce, axillae, neck. >80% of horses with sarcoids have more than 1 lesion. Often can be slow growing/quiescent for months/years, then rapid growth.

Lesions types: See: http://pcwww.liv.ac.uk/sarcoid/ for photos or Knottenbelt, Diseases and Disorders of the horse, Mosby. 

•   Verrucous (warty) Sarcoid: 

• Dry, horny and cauliflower-like, hairless and can have either a broad base or a stalk (pedunculated) 

• Fibroblastic Sarcoid:  

• Resembles proud flesh; can be firm and nodular and its surface may be ulcerated. 

• Mixed Sarcoid 

• This is a mix between any types of sarcoid. 

• Nodular Sarcoids:  

• Entirely under the skin, easily shelled out 

• Malevolent sarcoids: 

• Rare, most aggressive type - tumours spread extensively

  through the skin with cords of tumour tissue interspersed with nodules and ulcerating fibroblastic lesions. 

0. Difficult. Many tx’s available suggests no one is very effective. N.B. draw a lesion map so all lesions on horse at time of start of tx are documented. Lesions may increase in size and number after any interference. Choice of tx depends on site and type of sarcoid, cost issues etc. Lesions may occur at same or distant sites. Effective treatment is more certain if lesions are treated early, and if the horse is under 4 - 6 years of age. N.B. when comparing treatment ‘success’ must consider length of post-treatment evaluation.

1. Do Nothing: If do not cause interference e.g. with tack, are not ulcerated. Very occasionally sarcoids can be self-resolving.

2. Surgery: Up to 40% recurrence reported but better results (80%) if wide margins (8mm) taken or when used to ‘debulk’ large lesions which are then also tx’d with other therapy e.g. cisplatin. Laser surgery may also be useful (seals bv’s and lymphatics as it cuts). Ligation or elastration of stalks of pedunculated sarcoids sometimes effective.

3. Cryosurgery: Only effective for lesions with limited size and depth, may cause extensive damage to surrounding structures and scarring. High reported rate of recurrence.

   4. BCG injection: Very successful for periocular sarcoids (>85%), very poor rate of success elsewhere. Need 2-3 injections several weeks apart. Unknown mechanism of action. Can get severe anaphylactic reaction on repeat tx’s.

   5. Radiation -gives the best results but very expensive and very restricted (Liverpool only). Therefore, it is reserved for difficult lesions such as around the eye or over joints. 90-100% success at 1 year

   6. Topical cytotoxic therapy: AW4-LUDES (‘Liverpool sarcoid cream’) = secret formula applied topically on several occasions. Obtained on case by case basis from Leahurst Equine Hosptial. Causes skin necrosis and scarring. CARE: fly strike in tx’d areas in summer.

   7. Intralesional chemotherapy: Cisplatin (N.B. CARE when handling). 5-flourouracil.

   8. Combination therapy: usually gives best results. 

    

Prevalence: 4% of all tumours in horses, 10% of skin tumours in horses, 80% of grey horses >15y.o have them.
Classification: N.B. may change from benign  malignant

•   benign – tend to be dermal melanoma = discrete, slow growing, only cause probs if distorting normal function e.g. around anus, in guttural pouch.

•   Malignant – often metastasise. Grey horses = dermal melanomatiosis (>17 y.o.) or non-grey coloured horse = anaplastic malignant melanoma (>20 y.o.)

  Appearance: Black lesions, solid or soft, black on cut surface, aggressive melanomas can occasionally be amelanotic i.e. unpigmented.
  

0. Benign:

•   Leave alone – unless causing a problem

•   Excision – wide and check margins. May be curative for discrete dermal lesions or

  helpful for de-bulking large lesions that are causing a physical obstruction.

•   Cryotherapy – may need to repeat. Combine with de-bulking surgery? Don’t use if

  near any vital structures

•   Cimetidine – systemic oral tx. Only works in horses with lesions that are increasing

  fast in size or number. Poor client compliance because TID administration for 3

  months required. Expensive and very questionable success rate

•   Chemotherapy – intralesional cisplatin on at least 2 occasions. Cisplatin = v. toxic to

  the administrator so CARE when handling. 

0. Aetiology: UV radiation, chronic irritation, previous wound, smegma (penile SCC) Distribution: Usually around head/eye (esp 3rd eyelid) or external genitalia (vulva, penis), particularly non-pigmented skin.
   Appearance: lesions are productive (papillary appearance) or erosive (nodular plaques +/- ulceration). Locally invasive, slow to metastasize, maylocal lymph nodes then lung. 

0. Treatment:

•   Excision: wide, deep, check margins – often difficult around head, 55% recurrence rate. Good success for SCC of 3rd eyelid.

•   Cryotherapy (see above)

•   Radiation therapy: specialised centres only – iridium wire implants (U of Liverpool),

  strontium wands

•   Chemotherapy: topical 5% 5-flourouracil  90% success rate reported but have to

  apply daily for weeks. Cisplatin injection (see above)  65% success rate, when

  used in conjunction with surgical debulking  89% success.

•   Malignant lesions: only attempt to treat if reasonably sure have not metastasised. 

0. common disease of young horses (<2 y.o.) – due to papovavirus infection. Occasionally in older horses if immunologically naïve. Often on face/head, particularly around muzzle. Regress spontaneously in 3-4 months therefore NO NEED TO TX. Virus also causes aural plaques – see medicine skin lectures. 

rare in horse. Typically benign c.f. small animals. Arabs over represented. Surgical removal is usually curative. 

Definition = >105 bacteria/gram of tissue
o Bacteria prolong inflammatory phase of wound healing
o Bacteria may produce collagenases  decreased wound strength
o Predisposed to by devitalised tissue, foreign bodies, haematoma, seroma,

dead space, movement and excessive oedema.

you wasting lots of money on inappropriate drugs. 

particularly over high motion joints in the limbs

material) 

Large skin defect 

May just require more time if epithelisation is occurring

o May require skin graft (particularly on limbs where contraction effect = less)

o Delayed secondary closureskin to skin contact 

Presence of foreign body/necrotic tissue 

Stake wounds
o Inadequately debrided wounds
o Bone fragment remaining
o Bony sequestrum formation post-injury

Excessive granulation tissue = ‘Proud flesh’ (N.B. predisposed to by 1-4)

Limbs>>trunk wounds, Horses>> ponies
o Once granulation tissue protrudes higher than wound edge, v. difficult for

epithelium to grow over it.

Systemic disease of patient – N.B. has to be quite severe to affect wound healing 

Nutritional status of horse (i.e. cachexia)

o Cushings

Skin grafting not uncommonly required in horses due to poor wound healing in distal wounds and predisposition to exuberant granulation tissue. Reconstructive surgery/pedicle grafts difficult in horse due to practical considerations (little spare skin, difficult to mobilise etc.) 

Depends on:

•   Size and location of defect

•   Facilities and equipment available e.g.:

o Require GA e.g. to harvest split thickness grafts
o Specialist equipment e.g. dermatome
o Aftercare – require immobilisation/frequent bandage changes?

 Expertise available

Preparation of recipient site (for all types of graft) 

•   Need a fresh or granulating wound

•   If granulating, debriding granulation tissue prior to grafting reduces bacterial

  contamination of surface

•   DON’T consider grafting if infection present – may be obvious clinically or could do

  qualitative bacteriology on sample of granulation tissue (>105/g)

•   Consider topical tx of recipient site after initial debridement for 1 or 2 bandage

  changes prior to grafting (poor penetration of gran tissue by systemic abios). Beta- haemolytic streps and pseudomonads often a problem therefore consider silver sulfadiazine, nitrofurazone. 

0. 1. Pinch/Punch grafts: 

•   Easy to do – can be done in general practice on the yard – having another vet or nurse around speeds the process immensely.

•   Good for relatively small recipient sites

•   Donor site usually on dorsal aspect of neck, side hidden by mane

•   Reported up to 50% graft ‘take’ in horses – manage owner expectations 

0. 2. Tunnel grafts: 

•   Useful for large skin defects at highly mobile sites e.g. dorsal hock, or sites that are difficult to bandage e.g. thorax/abdomen/gluteal areas.

•   Technically simple

•   Donor site = neck, leaves more of a scar than pinch/punch 

• 3. Split thickness grafts: 

•   Very painful to harvest therefore horse usually requires GA

•   Need specialist equipment (dermatome)

•   Technically difficult but higher % ‘take’ than full thickness graft

•   No adnexal structures (hair etc) transferred (usually)

  4. Full thickness grafts: 

0. 4. Full thickness grafts: 

•   Good cosmetic and functional result – make sure hair is going correct direction!

•   Limited amount of donor skin available (usually take from brisket) – can mesh graft

  to make it cover larger area

•   Reduced survival c.f. split thickness. 

0.  Excessive movement and infection = most common. Both  fluid accumulation between graft and recipient site  prevent/disrupt adherence. Also inadequate preparation of graft (too thick?) or recipient site.