Image Quiz: Cytology-A chalky white-filled lesion in a German shepherd

Calcinosis circumscripta is a nonneoplastic degenerative lesion consisting of tumorlike nodules of mineralized foci surrounded by fibrosis and granulomatous inflammation (i.e. macrophages, multinucleated giant cells with or without lymphocytes, and neutrophils). The chalky white mineral is a critical clue to the diagnosis since this amorphous mineral tends to be difficult to appreciate after staining. Calcinosis circumscripta is usually seen as an idiopathic lesion occurring on the distal extremities, over the spine, and in the tongue of young large-breed dogs. The cause is not determined; since lesions occur at sites of potential injury, such as pressure points, mineralization may be dystrophic. Complete excision of individual lesions is curative.