Equine Cutaneous Mastocytosis

Abstract

A description of equine cutaneous mastocytosis is given. The lesion was characterized by focal aggregates of mast cells, and by eosinophils, fibrinoid necrosis of collagen, and focal necrosis with dystrophic mineralization of necrotic debris. This is an uncommon, previously undescribed lesion in horses. The authors encountered 14 cases in a 16-year period. The etiology and nature of the lesion are undetermined. Morphologic similarities to canine cutaneous mast-cell tumors, cutaneous lesions of collagen diseases, and calcinosis circumscripta are noted and the possibility of relationships to these lesions is discussed.