Other neoplasia

Question 1

Squamous cell carcinoma

Answer 1

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

Question 2

Most common forms of SCC in horses

Answer 2

Skin lesions

Genitalia lesions

Gastric lesions

Can crop up in any location

Head and neck SCC occasionally seen

Question 3

SCC skin lesions

Answer 3

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

Question 4

Genetic predispositions to SCC

Answer 4

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

Question 5

Genitalia SCC lesions

Answer 5

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

Question 6

Gastric SCC lesions

Answer 6

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

Question 7

Head and neck SCC lesions

Answer 7

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

Question 8

Presentation of SCC

Answer 8

typically presents as a cauliflower-like proliferative lesion OR as a destructive, ulcerative lesion in any location

Question 9

Treatment of SCC

Answer 9

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

Question 10

Possible topical/intralesional therapies for SCC

Answer 10

Mitomycin C

tigilanol tiglate

5-FU

Question 11

Mitomycin C to treat SCC

Answer 11

Intralesional or topical

Antimetabolite, cytotoxic – cross-links DNA

Temporary local irritation and conjunctival erythema/hyperaemia common

Very successful in humans

Question 12

Tigilanol tiglate as topical SCC treatment

Answer 12

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

Question 13

5-fluorocil as a topical treatment for SCC

Answer 13

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

Question 14

Staging of SCC

Answer 14

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,

Question 15

Staging of genital SCC lesions

Answer 15

Rectal examination is compulsory
- enlarged inguinal lymph nodes can sometimes be palpated

Abdominal ultrasound +/- abdominocentesis and cytology

Question 16

Staging of ocular or periocular lesions

Answer 16

URT endoscopy, including the guttural pouches

FNA or biopsy of regional LNN (submandibular)

Ideally a head CT should be performed

Question 17

Melanoma in horses

Answer 17

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

Question 18

Most common sites of melanomas in grey horses

Answer 18

perianal/perineal region,

under the tail,

on and inside the sheath, and

within the parotid salivary gland

Question 19

Treatment of melanoma

Answer 19

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

Question 20

Oncept melanoma vaccine

Answer 20

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.

Question 21

Lymphoma in horses

Answer 21

most commonly diagnosed haematopoeitic neoplasm but still rare

can occur at any age - most common 4-10yo

Variety of forms

Question 22

Forms of lymphoma in horses

Answer 22

Multicentric

Alimentary

Mediastinal

Cutaneous

Solitary

Question 23

Solitary lymphoma

Answer 23

frequently curable by wide local excision +/- radiotherapy

can look like almost anything

Question 24

Cutaneous lymphoma

Answer 24

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

Question 25

Commonly reported clinical signs of lymphoma in horses

Answer 25

weight loss,

lethargy,

ventral oedema,

recurrent fever,

and occasionally (but surprisingly, this is uncommon) peripheral lymphadenopathy is reported

Question 26

Chemotherapeutic principles for lymphoma in horses

Answer 26

Doxorubicin is most commonly used, but L-asparaginase, COP and CAP protocols have also been reported.

All are very expensive in horses.

Radiotherapy can be very useful for accessible lesions, because lymphoma is very radiosensitive.

Palliative treatment with prednisolone (1mg/kg SID PO) may allow for a reasonable quality of life for a short time (usually 3-6 months) in some GI and multicentric lymphoma cases.

Question 27

Haemangiosarcoma in horses

Answer 27

May present as a cutaneous lesion, be locally invasive, or as disseminated disease.

An unusual type of neoplasia in the horse.

Question 28

Common sites for haemangiosarcoma in horses

Answer 28

The lung and pleura,

skeletal muscle,

spleen.

Question 29

Common clinical signs of haemangiosarcoma in horses

Answer 29

dyspnoea,

swelling,

epistaxis,

lameness.

Question 30

Prognosis for haemangiosarcoma in horses

Answer 30

Disseminated disease has a hopeless prognosis, and locally invasive forms of the disease are unlikely to be treatable.

Cutaneous lesions may be surgically resectable in some cases. These resemble many other types of tumour and a biopsy is essential to establish a diagnosis.

Question 31

Mast cell tumour in horses

Answer 31

Usually benign and easy to treat

Can be found in any location

Respond well to surgical excision and/or intralesional corticostaroids

Radiotherapy may be required in tricky locations

Biosy essential

Antihistamines not required in horses

Question 32

Basal cell carcinoma in horses

Answer 32

Occasionally seen

Tend to look like sarcoids

Usually located on the distal limb or tail

Diagnosed via biopsy

Very successfully and simply treated with wide local excision

Question 33

Paraneoplastic syndromes in horses

Answer 33

look for a tumour whenever you have an unexplained clinical sign in a horse

Paraneoplastic pyrexia is the most commonly found

Cancer cachexia

Amyloidosis

Hypertrophic osteopathy (Maries disease)

Polycythaemia

Thrombocytopaenia

Hypercalcaemia

Hypocalcaemia

Monoclonal gammopathy

Paraneoplastic pruritis

Paraneoplastic pemphigus

Question 34

Paraneoplastic cancer cachexia

Answer 34

a wasting syndrome characterized by weight loss, anorexia, asthenia and anemia

Question 35

Paraneoplastic hypertrophic osteopathy

Answer 35

Maries disease

Symmetrical, painful proliferation of connective tissue and subperiosteal bone

Most commonly limbs, but also mandible, maxilla, nasal bones

In contrast to other species, usually associated with non-neoplastic thoracic disease in horses (tumours also implicated occasionally)

Question 36

Paraneoplastic polycythaemia

Answer 36

Liver tumours commonly implicated

May be first sign of neoplastic hepatic disease

Question 37

Paraneoplastic thrombocytopaenia

Answer 37

Especially common with lymphoma

Question 38

Paraneoplastic hypercalcaemia

Answer 38

Associated with multiple tumour types, especially gastric SCC

Question 39

Paraneoplastic pruritus

Answer 39

Lymphoma
Renal carcinoma