Pathomorphological features of calcinosis circumscripta in a dog.

A 19-month-old male German shepherd dog was presented with a hindlimb footpad mass. The mass was excised and histopathology was performed. Grossly, the cut section of the mass had multiple well-circumscribed nodules with a chalky appearance. Histopathologically, basophilic-stained calcium deposits of various sizes were distributed from dermis to subcutis, surrounded by epithelioid cells, multinucleated giant cells, and reactive fibroblasts. Myxoid metaplasia, calcium deposits in hair follicles, and psammoma-like bodies were also found. These histopathologic observations will greatly help to understand the pathogenesis of calcinosis circumscripta.