Unusual presentation of a mesenchymal eyelid hamartoma and an update of the incidence of periocular hamartomas in dogs

Abstract

A mesenchymal hamartoma in the dorsomedial eyelid of a Staffordshire bull terrier and the incidence and histological features of twenty-two canine mesenchymal periocular hamartoma cases are reported. The archives of the “Comparative Ocular Pathology Laboratory” of Wisconsin (USA) were searched for canine mesenchymal periocular hamartoma. Signalment, clinical appearance, location and histological findings are summarized for twenty-two dogs, containing fourteen different breeds, between four and fourteen years old. Fifteen hamartomas were located at the lateral canthus. Histologically, they consisted of fully differentiated fibrous tissue interspersed with adipose tissue, with bundles of skeletal/smooth muscle in ten cases, and peripheral nerve tissue in two cases. No mitotic figures were noted. Mesenchymal hamartomas may present as a subcutaneous, subconjunctival or orbital mass. Although they have a predisposition to occur at the lateral canthus, they may be located elsewhere on the eyelids or in the orbit.