Clinical presentation and diagnosis of calcinosis circumscripta in a one-year-old male Caucasian dog

Calcinosis is characterized by the deposition of calcium salts in or under the skin, often manifesting as firm, white plaques or masses. This condition can present in various anatomical locations and is commonly associated with inflammation and discomfort. When this deposition occurs in the dermis and subcutaneous tissues due to hyperadrenocorticism, dystrophic or idiopathic calcification, it is termed calcinosis cutis. On the other hand, when the calcification occurs as a result of repetitive trauma or at the site of buried sutures, it is termed calcinosis circumscripta and is usually based on the pattern of distribution. Accurate diagnosis and management are essential for improving the quality of life in affected animals. In this case, we report a diagnosis of calcinosis circumscripta in a 1-year-old male Caucasian dog presented with a firm, non-ulcerated, solitary mass on the right lateral proximal femur, which had been preceded by an abscess a year prior. Gross examination revealed a hard, cutaneous mass with multiple mineralized structures within thick fibrous connective tissue.  The mass was surgically excised and histopathologically evaluated. Microscopic examination showed variably sized circumscribed lakes of basophilic granular material surrounded by fibrous connective tissue without inflammatory cells, indicating Stage I calcinosis circumscripta. The findings suggest a dystrophic form of calcification, possibly enhanced by the active calcium metabolism in the rapidly growing dog and the history of a previous unresolved injection site abscess. This diagnosis was supported by the histopathologic findings and confirmed using Von Kossa stain as one of the special stains to demonstrate the calcium deposits. The case underscores the importance of detailed examination, histopathological and histochemical evaluation in the diagnosis and management of calcinosis circumscripta in Veterinary practice.