Pleomorphic sarcoma with giant cells infiltrating the infraorbital canal in an aged Thoroughbred mare

Abstract

SummaryA 27‐year‐old Thoroughbred mare presented for computed tomography (CT) of the head following a 3‐month history of facial swelling at the infraorbital foramen, unilateral self‐mutilation and head‐shaking. Standing CT imaging showed soft tissue attenuation surrounding the infraorbital canal, with extensive bony lysis of the canal and maxillary bone at the infraorbital foramen. The mare was subjected to euthanasia, and post‐mortem examination revealed a proliferative tan soft tissue mass overlying the infraorbital nerve. A histopathological diagnosis of pleomorphic sarcoma with giant cells was made. Immunohistochemical analysis failed to fully elucidate the mesenchymal cell of origin of the sarcoma. Pleomorphic sarcoma with giant cells involving the infraorbital canal of the horse has not been previously described. This case highlights chronic subtle behavioural changes attributable to this neoplasm prior to the development of clinical signs and the utility of advanced imaging in the diagnosis.