here - Australian College of Veterinary Scientists

5.Nodular type
Definition
Occurs as subcutaneous nodules and when these erode the overlying skin, they
become more aggressive fibroblastic type tumours
Clinical Presentation
Subcutaneous spherical nodules usually under normal skin(5-20mm). Most
frequently found in the groin or eyelid area Skin may become thin over larger
nodules. Where ulceration occurs, lesion quickly develops into fibroblastic sarcoids.
Differential diagnosis
Fibroma, neurofibroma, equine eosinophilic granuloma, melanoma, collagen
necrosis (axilla - rare), dermoid cysts.
Diagnosis
Biopsy: total excision if possible with wide margins
6.Malevolent type (Knottenbelt DC, et al 1995))
Definition
A recent variation of sarcoids showing increased malignancy with a suggestion of
metastasis adjacent to the initial site.
Clinical Presentation
Invasive sarcoid. Infiltration of lymphatics. Multiple tumours locally to metastatic
sarcoid in other lymph nodes. May follow surgical interference to sarcoids in jaw and
elbow region. Cords of tumour extend in lymphatics.
Differential diagnosis
Squamous cell carcinoma, subcutaneous mycosis, lymphangitis, glanders, enzootic
lymphangitis, cutaneous histoplasmosis.
Diagnosis
Clinical change to original sarcoid. Invasiveness of regrowth.
Reaffirmation of diagnosis of sarcoid from new invasive tissue.
General management consideration
Due to the uncertain outcome in 100% of cases, the horse owner should be very
aware of the seriousness of the problems which can arise from this disease.
Treatment should involve a full discussion of treatment options, on the likelihood of
successful treatment, and at worst, the likelihood of prolonged or repeated treatment
which, while the condition is contained, may not fully resolve it.
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ACVSC Proceedings Dermatology Chapter Science Week 2005