Equine skin masses Flashcards
what skin mass is this horse suffering from?
What type of horse sufferes from this?
Melanoma
* Mostly grey horses (Sullins 2021)
* White and lighter grey > darker grey, dappled and flea-bitten
(4-15% of all equine skin tumours)
what is the signalment of melanomas?
where do they occur?
Incidence increases with age
* All grey horses will develop melanomas over time
* Usually develop between 4-8 yrs
* Proportion of affected horses increases annually by 4-8% until 20 years old.
Base coat colours propensity (more likey to get) - Black > Bay > Chesnut
Typical locations:
* Tail
* Perineum
* Parotid region
* Commissure of lips/eyes
What is the cause of equine melanoma?
All grey horses have a gene mutation: STX17G
- Changes melanocyte behaviour
- Greying and more chance of vitiligo and melanomas
Disturbance in melanin transfer from dermal melanocytes to follicular cells
What are the different types of melanomas?
- Melanocytic nevi - Single or multiple discrete nodules
- Dermal melanoma - Originate in deeper dermis, Small singular or multiple nodules
- Dermal melanomatosis - Confluent large melanomas, Increased risk of metastasis
- Malignant melanoma - Not common, invasive, In older horses, Recurrence very likely
How can melanomas be graded?
- 0 - Free of melanoma
- 1 - Early stage of plaque type of single 0.5-cm nodule at typical locations
- 2 - Several 0.5-cm nodules, or single 2-cm nodule, at typical locations
- 3 - One or several nodules of 5 cm intra- or subcutaneous at typical locations or lips
- 4 - Extensive confluent subcutaneous melanoma with necrosis or ulceration, metastasis
- 5 - Exophytic tumor growth, with wet surfaces and ulceration, metastasis to organs with associated clinical signs (cachexia, fever, metabolic disorders)
How are melanomas diagnosed?
- Visual inspection
- Palpation
- Ultrasound
- Fine needle aspiration
What type of equine mass is this?
Melanoma - you can see melanin
What is the signalment of Anaplastic/amelanotic malignant melanoma?
where do they occur?
What is the prognosis?
- Non grey and grey horses
- Older horses
- Tail and tailhead +++
- Have metastasised by the time of diagnosis
- Rare
What equine skin mass is this?
What are the key features of this tumour?
Sarcoid - fibroblastic
- Benign
- Non-metastatic
- Locally aggressive
- In all equids
- High recurrence
- Affects up to 11.5% of horses
What are the 6 types of sarcoids?
- Occult
- verrucose
- Nodular
- Fibroblastic
- Mixed
- Malignant
what are the characteristics for occult sarcoids?
Describe them
- Mildest/most stable/superficial form of sarcoid
- Can remain unchanged for years
- Hairless skin
- 1 or more small (2-5 cm) cutaneous nodules or roughened areas with mild hyperkeratotic region surrounding
What are the characteristics of verrucose sarcoids?
- Rarely aggressive
- Rough hyperkeratotic appearance with some flaking or scaling
- Warty-looking
what are the characteristics of nodular sarcoids?
- Very variable sizes, 0.5 to 20 cm
- Firm, spherical, subcutaneous nodules
- Two types: - need to paplate to differentiate
- A: confined to subcutaneous tissues
- B: some involvement of overlying skin
What are the characteristics of fibroblastic sarcoids?
- Ulcerated, fleshy, aggressive appearance
- 2 types:
- 1: Pedunculated with limited/small base palpable under the skin
- 2: wide base, often diffuse/ill-defined margins
What are the characteristics of mixed sarcoids?
Mixture of two or more types of sarcoid
Vary between verrucous/occult/nodular to fibroblastic
What are the characteristics of malignant sarcoids?
Most severe, highly invasive
Infiltration of lymphatic vessels
Often following trauma or failed treatment
Cord of palpable tumour
what is the current though process behind the pathogenesis of saroids?
Bovine papillomavirus (BPV) type 1 (and 2)
* In sarcoid tissue but Also in normal skin
* Carriers: often sarcoid-affected horses and horses living with cattle
* BPV DNA also present in 30% of control population
* Not present in other tumour types
Transmission:
* Not fully understood
* Direct contact with horses with sarcoids
* Direct contact with cattle or horses carrying BPV
- BPV transmission by stable fly is possible
- More likely after the fly has been in contact with bovine papillomavirus than with horse sarcoids
what is the relationship behind trauma and sarcoids?
Neoplastic transformation of chronic wound into sarcoid has been described.
- How - Skin trauma –> direct access of BPV to subepidermal fibroblasts –> abnormal proliferation of fibroblasts
- Most sarcoids appear on trauma free skin
- Injuries like fly bites would go undetected…
what type of equine skin mass is this?
What are the key features?
what horses are often affected?
Squamous cell carcinoma
* Locally invasive, does metastasise
* Neoplasia of squamous epithelial cells
* Predilection for:
* areas lacking pigmentation
* Appaloosa/Quarter Horse/Clydesdales
* poorly haired
* mucocutaneous junctions
* external genitalia
* eye/adnexa
what are the predisposing factors for squamous cell carinoma?
What should you do if you suspect SCC?
- Equus Caballus papillomavirus 2 (EcPV2) and others
- Flies
- Smegma
- Ultraviolet light exposure
Procedure
* SCC does metastasise
* Should consider staging workup
* Even if treated can recur locally years later
* Do not ignore it!
What are the treatments for equine skin tumours?
What treatment is often used for sarcoids?
- Sharp excision
- Excisional biopsy (cut it of, then send off for pathology and then deal with the result after)
- Laser excision
- Currently favoured for sarcoids
- Frequently used for melanoma
- (Other: harmonic scalpel, cryosurgery, etc.)
Banding: For sarcoids with a thin peduncle only
* Not to be used if the mass has a root
* No evidence of success published, but still frequently used
* Takes a few weeks
* Leaves an open wound
Most successful with topical treatment too
What topical treatments can be used for sarcoids?
What intralesional chemotherapy can be used for equine skin masses?
What is the though process behind using elctrochemotherapy for skin masses?
Topical cream: For low mass burden only
* Do not use very close to eyes
* 5-Fluorouracil (Efudix ©) - 55% success, every day for 15 days
* Mitomycin C
* AW5 cream - 35% success - Complications, unpredictable
* Usually need multiple applications
* No standardised protocol
Intralesional chemotherapy
* Mitomycin C (0.04%)
* Tigilinol tiglate (Stelfonta)
* 5 fluorouracil
* Platinum-based
* Cisplatin - need PPE
* Carboplatin
Electrochemotherapy: uses electrical field pulses to induce increased cell membrane permeability to certain antitumour hydrophilic drug like cisplatin
- Vaccines - immunomodultory action
- Autologous
- Nitrogen deactivated for sarcoids
- APAVAC
- DNA vaccine (Oncept ©)
- Autologous
- radiotherapy
