Equine skin masses Flashcards
(45 cards)
1
Q
3 most common skin masses in horses
A
melanoma, sarcoids, SCC
2
Q
What is the most common skin cancer in horses?
A
- sarcoids
3
Q
What colour is predominantly gets melanomas?
A
- Greys
- white and lighter grey > darker grey, dappled and flea-bitten
4
Q
Base coat colour propensity for melanomas
A
- black > bay > chesnut
5
Q
What age do melanomas usually develop?
A
- 4-8y
6
Q
What coloured horse will all develop melanomas over time?
A
- greys
7
Q
Causes of melanomas in greys
A
- all have gene mutation STX17^G
- this mutation changes melanocyte behaviour
- greying and more chance of vitiligo and melanomas
8
Q
Cause of melanomas
A
- disturbance in melanin transfer from dermal melanocytes to follicular cells
8
Q
Types of melanomas
A
- melanocytic nevi
- dermal melanoma
- dermal melanomatosis
- malignant melanoma
9
Q
Characteristics of melanocytic nevi
A
- single of multiple discrete nodules
10
Q
Characteristics of dermal melanoma
A
- originate in deeper dermis
- small singular or multiple nodules
- more commonly on the dock and tail base
11
Q
Characteristics of dermal melanomatosis
A
- confluent large melanomas
- increased risk of mets
- more commonly around the perineum
12
Q
Characteristics of malignant melanoma
A
- uncommon, invasive
- in older horses
- recurrence very likely
13
Q
Typical locations of melanomas
A
- tail
- perineum
- parotid region
- commissure of lips/eye
(- but can get them anywhere)
14
Q
Melanoma diagnosis
A
- visual inspection
- palpation
- US
- FNA
15
Q
Characteristics of melanoma FNA
A
- full of melanin
16
Q
Why can melanomas (/any tumour) get infected (and potentially fly strike)?
A
- as they mature they can outgrow their blood supply and so become necrotic in the middle
- melanomas can start to ooze a really dark black pigmented material
17
Q
Anaplastic/amelanotic malignant melanoma characteristics
A
- non grey and grey horses
- older horses
- tail and tailhead +++
- have mets by the time of diagnosis
- rare
- tumour is so aggressive it outstrips it’s capacity to differentiate its cell properly -> they’re not pigmented cells
- why you should remove melanomas when they are removable
18
Q
Key features of sarcoids
A
- benign
- non-metastatic
- locally aggressive
- in all equids
- high recurrence
19
Q
Types of equine sarcoid
A
- occult
- verrucose
- nodular
- fibroblastic
- mixed
- malignant
20
Q
Features of verrucose sarcoids
A
- rarely aggressive
- rough hyperkeratotic appearance with some flaking or scaling
- warty-looking
- around the eyes and sheath are common places to find them
20
Q
Features of occult sarcoids
A
- mildest/most stable/superficial form
- can remain unchanged for years
- hairless skin
- 1 or more small (2-5cm) cutaneous nodules or roughened areas with mild hyperkeratotic region surrounding
- hardest to identify -> often need to clip the hair to identify
- don’t tend to be problematic unless in an awkward location
- can progress into other sarcoid types
- can get peri-ocularly which can make them very difficult to treat
- inner thigh is a common location
21
Q
Features of nodular sarcoids
A
- very variable sizes (0.5-20cm)
- firm, spherical, subcutaneous nodules
- 2 types: A (confined to subcutaneous tissues), B (some involvement of overlying skin)
- type A is easiest to treat as can shell it out
- recurrence relatively low if treated promptly and effectively
22
Q
Features of fibroblastic sarcoids
A
- ulcerated, fleshy, aggressive appearance
- 2 types: 1 (pedunculate with limited/small base palpable under the skin) and 2 (wide base, often diffuse/ill-defined margins)
- difficult to treat
- often very aggressive so need to treat promptly
23
Features of mixed sarcoids
- mix of two or more types of sarcoid
- vary between verrucous/occult/nodular to fibroblastic
24
Features of malignant sarcoids
- most severe, highly invasive, infiltration of lymphatic vessels
- often following trauma or failed treatment
- cord of palpable tumour
24
BPV (definition, link? to sarcoids)
- bovine papillomavirus type 1 (& 2)
- found in sarcoid tissue
- carriers: often sarcoid-affected horses and horses living with cattle
25
Transmission of sarcoids (theoretical)
- direct contact with horses with sarcoids (flies)
- direct contact with cattle or horses carrying BPV (flies)
- BPV transmission by stable fly is possible, but more lively after the fly has been in contact with BPV than with horse sarcoids
26
Areas commonly affected by sarcoids
- thinly skinned and/or thinly haired areas
- around the eyes, ears, axilla, ventral abdomen, inner thighs, sides of sheaths, mammary glands
26
Sarcoids and trauma
- neoplastic transformation of chronic wound into sarcoid has been described
- skin trauma -> direct access of BPV to subepidermal fibroblasts -> abnormal proliferation of fibroblasts
- BUT most sarcoid appear on trauma free skin, however injuries like fly bites would go undetected...
- granulation tissue can look like sarcoid tissue in a non-healing wound -> why we sometimes biopsy granulation tissue
26
Key features of SCC
- locally invasive, does metastasise
- neoplasia of squamous epithelial cells
- should consider staging workup
- can recur locally years after treatment
- DON'T IGNORE IT
27
Common places to find SCC
- penis
- vulva
- eye/adnexa
- can get them in the sinus (large before noticed)
- can get on the cornea
27
SCC predilection for
- areas lacking pigmentation (Appaloosa, Quarter Horse, Clydesdales)
- poorly haired
- mucocutaneous junctions
- external genitalia
- eye/adnexa (3rd eyelid)
28
Predisposing factors for SCC
- Equus Caballus papillomavirus 2 (EcPV2) and others
- flies
- smegma
- UV light exposure
29
Tx for equine skin masses
- surgical excision
- banding
- topic chemotherapeutics
- intralesional chemotherapy
- electrochemotherapy
- vaccines
- radiotherapy
30
Types of surgical excision and their use
- sharp excision (excisional biopsy)
- laser excision (currently favoured for sarcoids, frequently used for melanoma)
- harmonic scalpel
- cryosurgery
31
Banding
- for sarcoids with a thin peduncle only
- not to be used if the mass has a root
- takes a few weeks
- leaves an open wound
- no evidence of success published by still frequently used
- most successful in combination to topical tx
32
Topical chemotherapeutics (use, examples)
- for low mass burden only (e.g. thinner verrucose and occult lesions)
- also used for surgical sites with poor margins
- don't use very close to eyes
- 5-Fluorouracil (Efudix) (55% success for sarcoids, everyday for 15d)
- Mitomycin C (can use topically in the eye)
- AW5 cream (35% success, complications associated and unpredictable)
- usually need multiple applications
- no standardised protocol (all off licence)
33
Intralesional chemotherapy examples
- Mitomycin C (0.04%)
- Tigilinol tiglae (Stelfonta)
- 5 fluororacil
- Platinum-based (Cisplatin, Carboplatin)
34
Mitomycin C (use, cons)
- best for nodular masses
- often get leukotrichia (white hair) after tx so care if worried about cosmetics
- get white hair over where the cream was applied and also over the lymphatic where they're been draining the therapeutic agent (get veiny white hair appearance)
35
Stelfonta (use, cons)
- used for sarcoids and SCC in horses
- only used in some referral centres
- not always predictable (80% good, 20% get sloughing of face)
- used in studies around the eye
36
Cons of platinum-based intralesional chemotherapeutics
- human safety elements poor
37
Electrochemotherapy
- uses electrical field pulses to induce increased cell membrane permeability to certain anti-tumour hydrophilic drug (e.g. cisplatin)
- used peri-ocularly
38
Vaccines for skin masses
- autologous (nitrogen deactivated for sarcoids, APAVAC)
- DNA vaccine (Oncept)
39
Radiotherapy for skin masses
- only done at Cambridge
- sarcoids and SCC are very radiosensitive
