Flashcards in DR: Equine skin disease Deck (49):
3 commonest cutaneous neoplasms
* sarcoids *
Describe the nature of sarcoids
locally invasive, non-metastatic, fibroblastic, rarely regress spontaneously
Location - sarcoids
- any body part
- singly or clusters
- ventral abdomen, limbs, head, eyes, pinnae, lip commissures
- areas that have experienced trauma
Aetiology - sarcoids
- not definitively established
- ample evidence supports viral agent (high recurrence after complete excision as surgical trauma may induce proliferation and expression of latent virus --> tumour regrowth), flies, shared grooming equipment etc are possible transmission routes
Is susceptibility to sarcoids heritable?
Presentation - sarcoids
- linear or focal dermal thickening
- epidermis: varies, thick, rough and hyperkeratotic to ulcerated
- can occur in subcut tissue: firm, moveable masses, intact skin covering
What are the 6 distinct forms of sarcoids (this classification is not strictly histopathological)
- verrucous (warty)
(- above forms can quickly progress to more aggressive forms, especially if the area is traumatised)
Ddx for sarcoid suspicion
- linear hyperkeratosis
- rub marks
- equine eosinophilic granulomas
- pythiosis (infectious fungal disease)
Why is biopsy of occult/ nodular/ small verrucous tumours not recommended?
to avoid altering the morphology and behaviour of the lesion - definitive diagnosis based on histologica exam. punch biopsies not recommended
Tx - sarcoids
- wide range
- nothing universally effective
- selected on location, size, aggressiveness, clinical experience, client commitment, services, equipment, facilities
- surgical excision (50-64% recurrence, most within 6 months)
- intralesional implants containing chemotherapeutic agents allow high local drug concentration for extended periods (high molecular weight collagen matrix contains chemo agent and vasoactive modifier: tumours are injected 3-5 times at 2-3 week intervals
- Immiquimod (Aidara) stimulates WBCs
- intratumoral hyperthermia induced by orthovoltage
- cryotherapy with liquid nitrogen (cost effective in many cases)
- Eqstim - non-viable Propionibacterium acnes
- topical treatments
- various radioisotopes
- Immunotherapy - common, BCG most common immunomodulator
- autogenos vaccines
What is the 2nd commonest equine tumour?
SCC (20% of equine neoplasms). It is the most commonly diagnosed neoplasm of eye, conjunctiva, ocular adnex structures, external genitalia and others
How often do SCC metastasise? Where to?
19% cases - local LNs most commonly. Also lungs
What signalment is predisposed to SCC?
- older holders
- draft breeds, appaloosas, american paints and pintos
- stallions, geldings (smegma, persistent phimosis, repeated trauma)
Early CS of SCC
- thickening and mild exfoliation and ulceration
Mature SCC lesions
erosive or productive in nature
Ddx for SCC 4
sarcoids, melanoma, exuberant GT, pythiosis
Dx - SCC
- cytology and histology
- depending on size and site of lesion (excisional, wedge, punch or elliptical biopsy)
- others - FNA (noduar lesions), cytology (superficial scrapings) and impression smears
Tx - SCC
- most successful if initiated early
- debulking + cryosurgery
- intratumoral hyperthermia
- tpical tx of superficial ulcerative SCC (5-FU) drops and creams
- radiation therapy
- beta irradiation (strontium-90)
- course-fractionated cobalt 60 radiotherapy
- bloodroot extracts
How often does SCC recur after treatment?
Signalment - equine melanomas
- greater incidence in gray and white horses (when they occur in horses of other colours, they may be at greater risk of becoming malignant)
- arabians, thoroughbreds and percherons
- incidence, size and number of melanomas significantly correlates with age (67% prevalence at ages > 15 years)
- no gender predilection
What areas are most commonly affected by equine melanomas?
underneath the tail and the external genitalia. other regions too but less commobnly
Aetiology - equine melanomas
not clearly defined
- old gray horses: due to disturbed melanin metabolism --> formation of new melanoblasts OR increased activity in resident melanoblasts --> focal area of overproduction of pigment in dermis.
- UV light exposure (controversial - frequent exposure in shaded body regions)
How often do melanomas metastasise?
Infrequently - 95% melanomas are slow growing an show no signs of regional or distant metastasis.
Clinical significance - equine melanomas
of little clinical significance except when they inhibit use of riding tack or interfere with urination/defaecation/ coitus etc.
Appearance - melanomas
black or gray, solitary, discrete, firm, spherical or flat nodules in skin or subcutis, may have a pedicle. frequently coalesce, many together produce a cobblestone appearance. overlying skin may be intact or slightly alopecic
Outline melanoma metastatic transformation
occassionally melanomas exhibit slow growth for several years followed by sudden rapid growth associated with malignant trasnformation of tumour, become locally invasive and metastasise. rare instances rapidly grow and are malignant from onset.
Dx - equine melanomas
- generally based on gross appearance
- confirmed with histology ( mostly melanocytes and melanophages)
Tx - equine melanomas - 5
- often not necessary for small melanocytic tumours located in uncompromising locations
- large masses or those in nuisance areas - surgical excision (wide margin)
- cryosurgery can be used in conjunction with excision
- intralesional injection or implantation of cisplatin (effective if tumour <3cm diameter)
- cimetidine (histamine-R agonist. overall enhances immune function and targeting of tumours), regression should be noted within 3 months if not discontinue, monitor liver enzymes
List equine skin neoplasms
- rare mesenchymal neoplasms occasionally seen in skin include fibromas, basal cell tumours, lipomas and haemangiomas
What clinical features may be helpful in diagnosing a skin neoplasm?
- failure to respond to appropriate rational therapy
How can skin neoplasia and nodular disease be differentiated?
- presenting history and gross CS (experienced practitioner)
- histopathological diagnosis (for confirmation)
- biopsy and FNA sample analysis
Prognosis - equine sarcoids
- worse with advanced lesions or lesions in multiple sites
- small, well-defined tumours carry the best prognosis for surgical removal
- extensive areas of poorly defined verrucous and mixed sarcoid may result in rapid regrowth of a more aggressive sarcoid types
- worst scenario is when single fibroblastic or nodular lesions are removed from a surrounding area of occult or verrucous sarcoid
Prognosis - SCC
- Survival rates depend on the malignancy of the tumor and size before treatment.
- Tumors close to each other are more likely to spread or return within 20 weeks of surgical removal.
- Generally, when surgery fails to eliminate the tumors, the problem can be traced to late diagnosis and uncontrolled local disease rather than to spread of the cancer to distant tissues.
Prognosis - melanoma
- most are benign - excellent outcome
- congenital malignant melanomas are invasive but have little potential to spread to other organs - guarded
What were sarcoids previously called?
Ddx - for neoplastic skin disease
- nodular diseases
- proliferative ulcerative diseases
- chronic skin disease
- parasitic diseases
- epithelial and subcutanoeus swellings
Which virus has been implicated in equine sarcoids?
BPV1 and 2
What type of tumour are equine sarcoids?
mesenchymal tumour and the subepithelial accumulation of densely packed, hap-hazardly arranged fibroblastic cells can be seen histologically. If overlying epidermis is present, usually is hyperplastic or hyperkeratotic, especially flat sarcoids
What should you do with chronic non-healing wounds, especially on limbs?
suspect sarcoids and investigate this
Describe occult sarcoids
often circular, causes alopecia and irregular hair growth, can be confused with ringworm
Describe verrucose sarcoids
more advanced, irregular forms of occult sarcoids, have greater degree of overlying epithelial distortion. often seen in axillar or inguinal area
Describe nodular sarcoids
recognised as subcutaneous massess, often multiple, various sizes, well-circumscribed, usually dissected free, generally around eyes and inner thighs, larger lesions easily traumatised leading to progresion
Describe fibroblastic sarcoids
firm, ulcerated masses, disruption of overlying skin, vary in size, excessive GT, possibly pedunculated or thick base,
Describe mixed sarcoids
seen in many cases, comprise an irregular composition of 2 or more of aforementioned lesions
Describe malevolent sarcoids
rare variation of fibroblastic sarcoids, characteristically there is invasion of tumour along lymphatics, with development of further nodules along lymphatic chain, may result from interference of fibroblastic sarcoids.
What are the different clinical presentations of melanoma? 4
- melanocyte nevi
- dermal melanomas or melanomatosis
- anaplastic malignant melanomas (aggressive)
- amelanotic malignant melanomas (lack pigment and require histolopathology to aid dx)
What are SCC thought to develop from?
from progression of precancerous lesions
non-pigmented skin or MM, penile epithelium or in the clitoral region of mares