Use of thoracic computed tomography in the diagnosis of a pulmonary myxoma in a horse

Summary This case describes the first reported antemortem computed tomographic (CT) examination of the thorax in an adult horse. A 13‐year‐old Australian Stock Horse gelding presented for a severe cough, epistaxis and haemoptysis after a 1‐year history of suspected equine asthma. Thoracic radiographs revealed a variably well‐defined soft tissue mass with surrounding interstitial opacification. During a coughing episode, a mass was expectorated and histopathological evaluation was consistent with spindle cell neoplasia. Thoracic CT was performed using a 90 cm wide bore scanner and revealed a solitary soft tissue mass in the left caudodorsal pulmonary parenchyma, which post‐mortem histopathological examination confirmed to be a myxoma. High‐quality diagnostic images were obtained which allowed for detailed characterisation of the mass, its extent and spread. Pulmonary neoplasia, including myxoma, is rare in horses and represents a diagnostic challenge due to vague clinical signs and imaging limitations. This case report highlights the value and potential application of CT in equine thoracic disease, which should be considered for suspected pathology undetectable or poorly characterised by other imaging modalities, as well as for investigation of unresponsive or atypical respiratory cases.