Equine skin neoplasias Flashcards
(36 cards)
Main 4 skin neoplasias to affect horses.
- Melanoma
- Squamous cell carcinoma
- Sarcoids
- Papilloma
Describe Melanomas in horses.
- Cutaneous melanocytic tumours
- Second most common skin tumour in horses
- Very prevalent (80%) in older (>12y) grey horses but Can also occur in young or non-grey horses.
- No sex predisposition
Types of melanoma in horses. (3)
- Melanocytic naevus
- Dermal melanoma
- Dermal melanocytosis (multiple noduls)
- Malignant melanoma/melanosarcoma
identify
Melanocytic naevus
* Benign collection of melanocytes on superficial dermis (a freckle)
* Isolated, heavily pigmented and non-encapsulated
* Young horses
* Typically few lesions
identify
Dermal melanoma:
* Most common form of melanoma
* Affects older, grey horses
* Slow growth
* Spherical nodules
a) dermal melanoma = few discrete nodules
b) dermal melanomatosis = multiple, frequently confluent tumours
identify
Malignant melanoma/melanosarcoma
* Most aggressive form
* Rapid grow, ulceration, diffuse margins
* Malignant dissemination possible
* Variety of signs: colic, neurological, cardiac
How to: Diagnosis of melanoma in horses.
- Characteristic clinical appearance
- FNA, Cytology, Biopsy
– Cells with dark, granular melanin pigment
– Differentiation between benign and malignant - Rectal palpation
- Hematology, biochemistry
- Imaging with Endoscopy e.g. Guttural pouches
- CT, MRI also good
Treatment of equine melanoma. (4)
Surgical resection
* is the mainstay and often curative
* depending on location, not always feasible
Radiation therapy
* high efficacy but expensive
Chemotherapy
* Intratumoral injection with sesame oil (delays absorption) or topical placement of cytotoxic drugs
Immunotherapy
* antihistaine cimetidine
* a DNA vaccine against melanoma tumor-associated antigens
identify
periocular Squamous cell carcinoma in horses. can also be penile (see image).
- Common skin tumour
- Locally invasive but slow to metastasize
- Proliferative / ulcerative
Common locations:
– Poorly pigmented skin and mucocutaneous junctions
– Periorbital
– Genitalia (older horses, ♂ > ♀)
Risk factors:
– UV radiation exposure
– Poorly pigmented breeds
– Equine papillomavirus 2 (EcPV-2)
– Draft horses
identify
vulva Squamous cell carcinoma
– Clitoral: proliferative
– Labial: ulcerative
Squamous cell carcinoma diagnosis is based on (3+)
- Characteristic clinical appearance
- Impression smear
- Biopsy
- Other
– Genital: rectal exam
– Ocular: guttural pouch scope
– Scleral/corneal: Rose-Bengal staining
Tx of squamous cell carcinoma. (6)
- Surgical resection
- Cryotherapy
- Hyperthermia
- Photodynamic therapy
- Radiation therapy
- Chemotherapy
Describe surgical resection for treatment of squamous cell carcinoma.
Prognosis varies with location
– Very good for third eyelid (can be removed completely)
– Guarded for upper / lower eyelid
– Difficult for large masses in vulva
– Penis can handle:
* Resection of small masses
* Exision of tissues/ distal phallectomy
Describe cryotherapy for treatment of squamous cell carcinoma.
- Alone or following surgical debulking surgery.
- Minimal postoperative pain, reduced scarring and relatively low cost.
- Multiple treatments may be required and recurrence rates are relatively high.
Describe chemotherapy for treatment of squamous cell carcinoma.
Variable success depending on size, location, product used.
Topical:
* Easy, low systemic exposure
* Limited penetration, biohazard
* Imiquimod, 5-FU
Intralesional:
* High intratumoral concentration, accurate, safer for owner
* More difficult and perhaps more dangerous to apply
* 5-FU,Cysplatin
Prognosis for squamous cell carcinoma in horses.
- Most are fairly local
- Local spread is rare but still more common than metastatic dissemination.
- Poor prognosis if involvement of local lymph nodes.
- Poor prognosis with penile form in young geldings e.g. “wooden” feel to penis is a bad prognostic sign.
Describe Sarcoids in horses.
- Most common skin tumour in horses
- Tumour of fibroblasts
- Only affects the skin: no metastasis through the rest of the body
- Can be aggressive locally
- Affects all Equidae
- No sex predilection
- Number of sarcoids on an individual horse is variable.
Sarcoid 6 clinical presentations:
Occult = Flat, hairless, gray scaly areas (often look like ringworm)
Verrucose = Warty, dry, crusty—may resemble papillomas.
Nodular = Firm, subcutaneous lumps under intact skin
Fibroblastic = Fleshy, ulcerated, bleed easily—often confused with proud flesh (excessive granulation tissue).
Mixed = Combination of two or more types
Malignant = Rare, aggressive, infiltrative along lymphatics—seen in younger horses.
Occult sarcoid
Occult = Flat, hairless, gray scaly areas (often look like ringworm)
Verrucous sarcoid
Verrucose = Warty, dry, crusty—may resemble papillomas.
Nodular sarcoid
Nodular = Firm, subcutaneous lumps under intact skin
Fibroblastic
Fibroblastic = Fleshy, ulcerated, bleed easily—often confused with proud flesh (excessive granulation tissue).
mixed sarcoid
Mixed = Combination of two or more types
Malignant sarcoid
Malignant = Rare, aggressive, infiltrative along lymphatics—seen in younger horses.
