CT features of primary bone neoplasia of the thoracic wall in dogs

Primary thoracic wall neoplasia is uncommon in dogs and the prognosis depends on tumor type. The aims of this retrospective, multi-center, observational study were to describe CT features of primary thoracic wall neoplasia in dogs and to test the hypothesis that CT features would differ among tumor types. Dogs with a diagnosis of primary thoracic wall bone neoplasia and thoracic CT study were included. CT findings recorded were as follows: dimensions, location, invasiveness, grade and type of mineral attenuation, periosteal reaction, contrast enhancement, and presence of presumed pulmonary metastases, pleural effusion, and sternal lymphadenopathy. Fifty-eight cases were included (54 ribs and four sternum). Fifty-six were malignant (sarcomas - SARC) and two were benign (chondromas - CHO). Out of the 56 malignant tumors, 41 had histological confirmation of the tumor type: 23 (56%) osteosarcomas (OSA), 10 (24%) chondrosarcomas (CSA), and eight (20%) hemangiosarcomas (HSA). The majority of rib tumors were right-sided (59%) and ventrally located (72%). Malignant masses showed severe invasiveness, mild/moderate contrast enhancement, and different grades of mineral attenuation. Sternal lymphadenopathy was significantly more frequent in dogs with OSA and HSA compared to dogs with CSA (p = 0.004 and p = 0.023). Dogs with HSA showed significantly lower mineral attenuation grades compared to dogs with OSA (p = 0.043). Primary thoracic wall bone neoplasias were more frequently arising from the ribs, with only a few cases of sternal masses. Findings can be used to help prioritize differential diagnoses for CT studies of dogs with thoracic wall neoplasia.