Case Report: Poorly differentiated malignant mesenchymal neoplasm presenting as a thoracolumbar spinal mass in a pet rabbit (Oryctolagus cuniculus)

Spinal masses in rabbits are rarely reported but may lead to severe neurological deficits. We describe the clinical presentation, diagnostic imaging findings, surgical management, and outcome of a 7-year-old male pet rabbit ( Oryctolagus cuniculus ) presenting with progressive paraplegia of the pelvic limbs. Complete hematological and biochemical evaluation, followed by computed tomography (CT), were performed. CT imaging identified a compressive thoracolumbar lesion at the T11–T12 level associated with perifocal osteolysis of T11. Initial medical management with steroidal anti-inflammatory drugs (prednisone) failed to improve neurological status. A T11–T12 mini hemi-laminectomy was therefore performed to relieve spinal cord compression and allow mass removal. Intraoperatively, moderate osteolysis of T11 and marked lysis of the T11–T12 annulus fibrosus and articular facets were observed without evidence of pathological fractures. Following removal of the mass, the spinal cord cranial to the lesion showed macroscopic changes consistent with myelomalacia. Postoperative neurological assessments between 24 and 72 h revealed progressive neurological deterioration, including tetraparesis and absence of caudal cutaneous reflexes. Due to progressive myelomalacia and poor prognosis, the rabbit was euthanized four days after surgery. Histopathological examination revealed a poorly differentiated malignant mesenchymal neoplasm, with meningioma considered one possible differential diagnosis based on anatomical location and histomorphological features; definitive classification was limited by the very small amount of available tissue and the limited immunophenotypic characterization. The total survival period from onset of clinical signs to euthanasia was 42 days. Necropsy was declined by the owner; therefore, metastatic disease could not be assessed. This case highlights the diagnostic uncertainty associated with a poorly differentiated malignant mesenchymal neoplasm presenting as a spinal mass in a pet rabbit.