Radiographic features of equine vertebral neoplasia

Introduction / Purpose: Neoplasia involving the equine skeletal system is uncommon, with a prevalence of less than 1.5%. There are a few single published case reports describing vertebral tumours in horses. The aim of this study is to describe the radiographic features of equine vertebral neoplasia. Methods: A multicentre retrospective search of horses with histologically confirmed vertebral neoplasia and available radiographs of the area was performed. Radiographs were reviewed by two observers simultaneously and multiple radiographic features for each case were recorded (location, number of lesions, type of osseous changes, soft tissue involvement). Results: Eleven horses met the inclusion criteria. Final diagnoses included haemangiosarcoma (n=4), spindle cell sarcoma (n=2), osteosarcoma (n=2), undifferentiated sarcoma (n=2) and adenocarcinoma (n=1). Ataxia and stiffness were the most common clinical signs. Lesions were mainly identified in the cervical spine (10/11), with the ventral vertebral compartment being the most common location. A definitive radiographic pattern was not established, but all lesions were osteolytic with an osteoproliferative component in 7 out of 11. Polyostotic lesions and pathological fractures were identified in 3 and 4 horses, respectively. Horses with haemangiosarcoma had multiple lesions in other sites on necropsy. Discussion / Conclusion: Although neoplasia is an extremely rare disorder of the equine spine, it should be considered as a differential diagnosis when monostotic or polyostotic aggressive lesions are identified, especially affecting the ventral compartment and/or the cervical region. In horses with haemangiosarcoma, the most common type of neoplasia in this study, a thorough exam is recommended in order to identify additional lesions.