Case Report: Feline spinous process giant-cell osteosarcoma.

Two adult domestic shorthair cats were evaluated for progressive neurologic deficits caused by spinal cord compression secondary to vertebral osteosarcoma, giant-cell subtype. Feline giant cell osteosarcoma represents a rare tumor type, particularly uncommon in the vertebral column. The cats showed progressive paraparesis or hemiparesis, with neuroanatomic localization to C1-C5 and T3-L3 respectively. Magnetic resonance imaging revealed a single, well-demarcated osseous mass arising from the spinous process for and lamina for each patient (case 1 at C6 and case 2 at T4). Both lesions produced marked >50% dorsal spinal cord compression and were isointense to the spinal cord on T1-weighted images and hypointense on T2-weighted images. Cytology prior to surgical intervention was performed in one case, confirming sarcoma diagnosis, and both affected cats underwent a dorsal laminectomy procedure, involving the removal of the affected spinous process and lamina. Histopathology was performed for both patients and confirmed giant cell osteosarcoma in both cases and additional features consistent with the telangiectatic subtype of osteosarcoma in one case. Post-operative recovery included initial resolving of presenting clinical signs, though both cats ultimately experienced recurrent neurological deterioration consistent with local tumor recurrence, leading to euthanasia. These cases illustrate that spinal giant cell osteosarcoma should be considered in cats with progressive myelopathy. They demonstrate that surgical decompression alone can provide substantial neurological improvement, with the potential for medium-term stability or remission. As local tumor recurrence caused eventual relapse of clinical signs, improving pre-, and intraoperative tumor margin identification and applying adjuvant treatments may improve longterm outcome, and should be investigated in future cases.