MRI and CT Findings of a Rare Extradural-Extramedullary Lumbar Hemangiosarcoma in a Dog: A Case Report

An 8-year-old neutered male Australian Shepherd was presented for evaluation of acute lumbosacral pain and reluctance to walk. Magnetic resonance imaging (MRI) of the lumbar spine revealed a well-demarcated, extradural-extramedullary left lateralized mass extending from L6 to L7 vertebrae, displacing and compressing the conus medullaris and the cauda equina, including the left sciatic nerve roots. The mass was T1-weighted hypointense, T2-weighted, and STIR homogeneously hyperintense, with partial contrast enhancement. Most likely diagnosis was a malignant neoplastic process, in particular sarcoma, without excluding an inflammatory process. Surgical decompression with a dorsal laminectomy was performed, and histopathology confirmed a diagnosis of hemangiosarcoma. Thoracic and abdominal computed tomography (CT) subsequently identified pulmonary nodules, with many exhibiting well-defined margins, a peripheral ground-glass halo sign, and feeding vessel signs, features highly characteristic of metastatic hemangiosarcoma. Additional hepatic and subcutaneous nodules further supported systemic metastasis. To our knowledge, this is only the second report of an extradural-extramedullary lumbar hemangiosarcoma in a dog and the first to include complete metastatic staging using CT. In this case, associating MRI and CT was particularly informative: MRI provided detailed characterization of the spinal mass, whereas CT revealed a metastatic pattern highly consistent with hemangiosarcoma. This integration of modalities demonstrates how a common tumor may present differently in an uncommon location and how advanced multimodal imaging influenced diagnostic and staging. These findings underscore the need to consider hemangiosarcoma among differential diagnoses for extradural spinal masses and highlight the clinical value of comprehensive imaging when evaluating potentially malignant spinal lesions.