19.4.2: The lumpy horse Flashcards
Melanoma
* Occurs mostly in grey horses (more common in whit and lighter greys compared to dark, dappled grey and flea bitten)
* Usually develops 4-8 y.o. and change increases with age
Aetiology of melanomas
Types of melanomas
Typical melanoma locations
- Tail
- Perineum
- Parotid region
- Commisure of lips / eyes
Diagnosis of melanoma
- Visual inspection
- Ultrasound
- FNA
Signalment for malignant melanoma
a.k.a. anaplastic malignant melanoma
* Seen in older, non-grey horses
* Tail and tail heads = very common site
* Have metastasised by the time of diagnosis
* Rare
Sarcoid
Characteristics of equine sarcoids
- Benign, non-metastatic
- Locally aggressive
- Found in all equids
- Have high recurrence
Types of sarcoids
- Occult
- Verrucose
- Nodular
- Fibroblastic
- Mixed
- Malignant / malevolent
Characteristics of occult sarcoids
- Mildest/ most stable/ most superficial form of sarcoid
- Can remain unchanged for years
- Hairless skin
- 1 or more 2-5 cm cutaneous nodules or roughened areas with mild hyperkeratotic region around
Occult sarcoids
Characteristics of verrucose sarcoids
- Rarely aggressive until injuried
- Rough hyperkeratotic appearance with some flaking or scaling around it
- Warty-looking
Verrucose sarcoid
Characteristics of nodular sarcoids
- Usually not an issue until injuried
- Firm, spherical, subcutaneous nodules of variable sizes (0.5-20cm)
- 2 types: Type A confined to subcutaneous tissues, Type B have some involvement of overlying skin
Nodular sarcoid
Characteristics of fibroblastic sarcoids
- Ulcerated fleshy aggressive appearance
- 2 types
- Type 1: pedunculated with limited/ small base palpable under the skin
- Type 2: wide base, often diffuse / ill-defined margins
Fibroblastic sarcoid
Characteristics of mixed sarcoids
- Mixture of 2 or more types of sarcoids
- Transient state between verrucous/ occult/ nodular to fibroblastic
Mixed sarcoid
Characteristics of malignant / malevolent sarcoids
- Most severe, highly invasive form
- There is infiltration of lymphatic vessels
- Often following trauma or failed treatment
- There is a cord of palpable tumour
Causes and transmission of equine sarcoids
Causes
* Bovine papillomavirus (BPV) type 1 and sometimes 2 is found in the sarcoid tissue but also in normal skin of several horses
* Carriers = sarcoid-affected horses and horses living with cattle
* BPV is one factor among others
Transmission
* Not fully understood
* Direct contact with sarcoids/ direct contact with cattle or horses carrying BPV
* BPV transmission by stable fly is possible
* More likely after fly has been in contact with BPV than horse sarcoids
How could sarcoids develop after trauma?
- Skin trauma allows BPV direct access to the subepidermal layer, and can lead to abnormal proliferation of fibroblasts
- However sarcoids do appear on wound-free skin too
Characteristics of equine squamous cell carcinoma
- Second most common tumour in the horse
- Locally invasive
- Predilection for areas lacking pigmentation (Appaloosa, Quarter Horse, Paint Horse), poorly haired areas, mucocutaneous junctions, external genitalia
- Most common neoplasia of the equine eye -> affects the conjunctiits and ocular adnexal structurs
SCC
