Page 81 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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7.6 Calcinosis
VetBooks.ir Deposition of mineral (mostly containing calcium) in the dermis, and/or subcutis.

Clinical features
• Reported in dogs and only rarely in cats.
• Mineralization can be dystrophic, metastatic, idiopathic or iatrogenic. Three major
forms of calcinosis are described:
• Calcinosis cutis: this term is used in veterinary medicine to denote widespread
dermal mineralization occurring with endogenous or iatrogenic steroid adminis-
tration (especially long-acting injectable corticosteroids). It may evolve to osteoma
cutis (metaplastic bone) in late stages.
• Calcinosis circumscripta: usually focal, nodular deposition of mineral salts in the
subcutaneous tissue. Most cases are deemed idiopathic, though might be dys-
trophic secondary to focal trauma and long-lasting local ischaemia.
• Systemic mineralization: deposition of calcium salts may also occur secondary to
renal failure, underlying neoplasms or it may be iatrogenic secondary to injection
of calcium-based products.
• Single or multiple pale yellow to white papules, plaques, or nodules, often coalescing
and releasing gritty white material upon aspiration. These may become ulcerated and
infected. Calcinosis circumscripta mostly presents as a single, well defined, subcuta-
neous nodule.
• Anatomical locations are variable:
• Calcinosis cutis: observed more often in skin regions subject to repetitive flexure.
• Calcinosis circumscripta: observed at sites of potential trauma (e.g. pressure
points, bone prominences), tongue and ears and in the paw pads secondary to
renal disease.
• Systemic mineralization: calcium salts tend to deposit in organs rich with nega-
tively charged elastic fibres, such as lungs, stomach, but may also involve the skin.
Prognosis is good after surgical excision of calcinosis cutis.
• Over-represented canine breeds:
• Calcinosis cutis: Bulldog, Labrador Retriever, Rottweiler, Boxer and Staffordshire
Bull Terrier (often secondary to iatrogenic hyperadrenocorticism).
• Calcinosis circumscripta: young, rapidly growing large-breed dogs, especially
German Shepherd and brachycephalic dogs, such as Boston Terrier and Boxer,
which are predisposed to dystrophic and idiopathic forms.

Cytological features
• Cellularity is generally low.
• Background: pale grey-basophilic with numerous variably small and irregularly shaped
refractile structures with angular borders. These are better appreciated with a lowered
microscope condenser.