CPD Article | EQUINE
• This represents an advanced stage but it can
develop abruptly following trauma to any other
form of the disease at any site.
• No current treatment.
• Very poor prognosis.
• Fibrosarcoma, spindle cell sarcoma, neurofibromas
and fibromas are probably variants of the sarcoid
(similar in gross appearance to sarcoid but some
have histologically distinct features).
Histopathology findings
Diagnostic investigation
Histopathology
• Biopsy.
• Do not biopsy unless you can treat the lesion as
soon as results available.
Biopsy may àprogression of lesion to more aggressive
form
Confirmation of diagnosis
Discriminatory diagnostic features
• History and clinical signs.
Definitive diagnostic features
• Diagnosis on clinical grounds is reasonable,
avoiding the need for biopsy which often triggers
an exacerbation. The presence of several dermal
tumors and changes that are consistent with one
or more of the recognized types is probably highly
supportive, but cases may be complicated by
another condition altogether.
• Biopsy is characteristic histologically, although
sometimes pathologists are reluctant to commit
themselves to the diagnosis if there are no
epidermal components, however, this is unjustified
and it should be entirely feasible to make the
diagnosis from tissue that has no overt dermal or
epidermal tissue.
• Epidermal and dermal components.
• The epidermis (where intact) is acantholytic and
hyperkeratotic with characteristic epithelial pegs
extending into the dermis.
• Whorled fibroblasts and varying amounts of
interstitial collagen.
• Haphazard vascular patterns will differentiate
fibroblastic forms from granulation tissue.
• Mitotic rates and doubling times are very variable
but the former is usually slow while the latter is
slow.
• Predominance of one component over the other
depends upon type of sarcoid and degree of
surface ulceration.
Differential diagnosis
Type I - Occult
• Alopecia areata.
• Dermatophytosis.
• Hyperkeratosis/skin irritation, eg from tack rubs.
• Ectoparasites.
• Insect bites.
Type II - Verrucose
• Papillomatosis.
• Hyperkeratosis.
• Squamous cell carcinoma.
• Habronemiasis.
• Bacterial/fungal granulomas.
• Cheloid scar.
• Equine sarcoidosis.
• Molluscum contagiosum.
• Horse pox.
• Volume 21 Issue 3 | September 2019 •
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