Other neoplasia Flashcards
Squamous cell carcinoma
There are a number of different ‘syndromes’ of SCC in horses, with likely different pathogenesis.
The end result is the same, with the same neoplastic transformation regardless of the inciting cause
Most common forms of SCC in horses
Skin lesions
Genitalia lesions
Gastric lesions
Can crop up in any location
Head and neck SCC occasionally seen
SCC skin lesions
Usually in non-pigmented skin secondary to solar exposure
found on the third eyelid, limbus, cornea, and in any area of pink skin (nose, periocular)
Although many are the classic ‘cauliflower-like’ proliferative lesions, ulcerative forms also occur
Suspect SCC in any unusual ocular or periocular presentation
Genetic predispositions to SCC
Haflinger horses, Belgian Warmbloods, and Rocky Mountain Horses, there is a known predisposition to the development of limbal and third eyelid SCC
associated with a mis-sense mutation in damage-specific DNA binding protein 2
Genitalia SCC lesions
Uncertain aetiology, possibly associated with equine papillomavirus-2
broadly analogous to HPV-mediated SCC in humans
Wide local excision can be curative but metastasis must be ruled out
En bloc resection may be required
often diagnosed late, and metastasis is common, as is recurrence
prognosis is therefore poor
Gastric SCC lesions
Uncertain aetiology.
Occasional cause of weight loss, secondary gastric impactions, colic, and other vague clinical signs.
Rare
Diagnosed when a mass is noted on gastroscopy, definitive diagnosis achieved via transendoscopic biopsies
often located at the pylorus, they can crop up anywhere in the stomach and are often diagnosed at an advanced stage with metastasis already present
no treatment, so the prognosis is very poor
Head and neck SCC lesions
Especially SCC within the sinuses which often presents like any other form of sinusitis.
by the time of diagnosis these are often extremely extensive lesions, with wide bony destruction and tooth loss commonly found along with the lesions.
The prognosis is very poor where surgical resection is not possible
Presentation of SCC
typically presents as a cauliflower-like proliferative lesion OR as a destructive, ulcerative lesion in any location
Treatment of SCC
Wide surgical excision
exquisitely sensitive to radiotherapy and this is a useful primary or adjunctive treatment
Ocular and periocular SCC control rates are excellent with strontium plesiotherapy
Topical and/or intralesional treatments may also be useful
Piroxicam/firocoxib
Possible topical/intralesional therapies for SCC
Mitomycin C
tigilanol tiglate
5-FU
Mitomycin C to treat SCC
Intralesional or topical
Antimetabolite, cytotoxic – cross-links DNA
Temporary local irritation and conjunctival erythema/hyperaemia common
Very successful in humans
Tigilanol tiglate as topical SCC treatment
Licensed for the treatment of mast cell tumours in dogs
Could be suitable for any tumour type
Acute inflammatory response
Haemorrhagic necrosis
Leads to sloughing and re-epithelialisation
Risk of uveitis – must place SPL and use prophylactic topical NSAIDs & Atropine and systemic NSAIDs
5-fluorocil as a topical treatment for SCC
Structural analogue of thymine, inhibits DNA formation by blocking enzyme thymidylate synthetase
Rapidly dividing (tumour) cells require more DNA and RNA than normal cells so take up larger amounts of 5-FU
Chemotherapy – use SPL, wear gloves
Staging of SCC
6-18% of cases will have metastasised at first presentation
Primary SCC with no metastasis has a good prognosis IF wide local excision can be performed
Where metastasis has occurred and/or margins cannot be obtained, the prognosis becomes guarded to poor.
Metastasis does not preclude treatment,
Staging of genital SCC lesions
Rectal examination is compulsory
- enlarged inguinal lymph nodes can sometimes be palpated
Abdominal ultrasound +/- abdominocentesis and cytology
Staging of ocular or periocular lesions
URT endoscopy, including the guttural pouches
FNA or biopsy of regional LNN (submandibular)
Ideally a head CT should be performed
Melanoma in horses
tend to be relatively benign lesions
seen in middle aged to older grey horses - almost ubiquitous in the older grey horse population
occasionally seen in other colours of horse
can be found anywhere, including in the eye
grow and multiply over the horse’s lifetime
can become necrotic, ulcerated, and lead to functional problems
can eventually metastasise
Most common sites of melanomas in grey horses
perianal/perineal region,
under the tail,
on and inside the sheath, and
within the parotid salivary gland
Treatment of melanoma
early surgical excision
Not every lesion is amenable e.g. in the parotid salivary gland
- many horses will also have small lesions within their guttural pouches and these should not be tampered with
Oncept melanoma vaccine, which is a xenogeneic human DNA vaccine against tyrosinase
Oncept melanoma vaccine
licensed for the treatment of melanomas in dogs
administered intradermally via a special applicator
safe and leads to antibody production in horses, with few or no side-effects
may lead to stabilisation of the disease
unlikely to lead to regression of lesions already present
best used in relatively early cases
large, necrotic masses are unlikely to derive much – if any – benefit.
Lymphoma in horses
most commonly diagnosed haematopoeitic neoplasm but still rare
can occur at any age - most common 4-10yo
Variety of forms
Forms of lymphoma in horses
Multicentric
Alimentary
Mediastinal
Cutaneous
Solitary
Solitary lymphoma
frequently curable by wide local excision +/- radiotherapy
can look like almost anything
Cutaneous lymphoma
can present as solitary or multiple nodular skin lesions
surgical excision is potentially curative
adjunctive treatments that have been used are oral progesterone and oral prednisolone, which are likely to be only palliative in nature
