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Background: Histiocytic sarcoma (HS) is an aggressive malignant neoplasm, and widespread metastasis occurs with a fatal outcome. HS involving the central nervous system is relatively uncommon. Spinal cord necrosis, a very rare condition, could be induced by ischemia or infarction. Here, we report a dog progressing non-ambulatory tetraparesis with spinal cord necrosis caused by HS. Case Description: A 9-year-old male Labrador retriever was presented with a progressing non-ambulatory tetraparesis. CT imaging revealed lysis of the spinous process of T7 and a ring-shaped lesion surrounding the soft tissue of lung fields. T2-weighted MRI showed the spinous processes of T6 to T8 as hyperintense, and the lesion infiltrated into the T7 vertebra and the spinal cord. After euthanasia, the final diagnosis upon necropsy was HS, which was observed in the lung, spinous process, thoracic cord, and the pulmonary hilar lymph node. Moreover, necrotic spots were spread widely through the thoracic spinal cord. Conclusion: This report outlines a case of canine HS in the lung, spinous process, thoracic cord, and pulmonary hilar lymph node. Ischemic deficit and necrosis of the thoracic spinal cord resulted from the compression of perivascular tumor cells, which rapidly led to progressive tetraparesis. Although the diagnosis was difficult, MRI and CT images helped determine the prognosis. To our knowledge, this is the first case report of canine HS with direct spinal cord involvement associated with spinal necrosis. [Open Vet J 2023; 13(3.000): 394-399]

Background: The anti-programmed death 1 (PD-1) antibody has led to durable clinical responses in a wide variety of human tumors. We have previously developed the caninized anti-canine PD-1 antibody (ca-4F12-E6) and evaluated its therapeutic properties in dogs with advance-staged oral malignant melanoma (OMM), however, their therapeutic effects on other types of canine tumors remain unclear. Objective: The present clinical study was carried out to evaluate the safety profile and clinical efficacy of ca-4F12-E6 in dogs with advanced solid tumors except for OMM. Methods: Thirty-eight dogs with non-OMM solid tumors were enrolled prospectively and treated with ca-4F12-E6 at 3 mg/kg every 2 weeks of each 10-week treatment cycle. Adverse events (AEs) and treatment efficacy were graded based on the criteria established by the Veterinary Cooperative Oncology Group. Results: One dog was withdrawn, and thirty-seven dogs were evaluated for the safety and efficacy of ca-4F12-E6. Treatment-related AEs of any grade occurred in 13 out of 37 cases (35.1%). Two dogs with sterile nodular panniculitis and one with myasthenia gravis and hypothyroidism were suspected of immune-related AEs. In 30 out of 37 dogs that had target tumor lesions, the overall response and clinical benefit rates were 6.9% and 27.6%, respectively. The median progression-free survival and overall survival time were 70 days and 215 days, respectively. Conclusions: The present study demonstrated that ca-4F12-E6 was well-tolerated in non-OMM dogs, with a small number of cases showing objective responses. This provides evidence supporting large-scale clinical trials of anti-PD-1 antibody therapy in dogs. [ABSTRACT FROM AUTHOR]