Electrochemotherapy in the treatment of maxillary multilobular bone tumor in a dog: clinical, histopathological, and tomographic findings.

Multilobular Bone Tumor (MBT) is a rare, slow-growing, and locally invasive neoplasm in middle-aged to older dogs, occurring predominantly in flat bones of the skull, pelvis, or ribs. This work reports the case of a 10-year-old, castrated, male Schnauzer, presenting with a tumorous growth in the incisor region measuring 1.0 x 0.7 x 0.6 centimeters for 30 days. Excisional biopsy revealed polygonal, hyperchromatic mesenchymal cells with oval nuclei and condensed chromatin, confirming a well-differentiated MLTB. However, the tumor recurred within 5 months, measuring 3.3 x 2.4 centimeters in the same region. Computed tomography (CT) revealed a mixed bone reaction, predominantly lytic, involving the incisive bone at the level of the incisor and canine teeth. The owner declined rostral maxillectomy and opted for a palliative approach with electrochemotherapy (bleomycin 15,000 UI/m2) at the tumor site. Complete remission was achieved within 28 days with macroscopic areas suggestive of scarring. The disease-free interval was 365 days without adjuvant therapy. However, at 435 days post-procedure (D0), recurrence was observed in the incisor region, accompanied by respiratory distress. Staging revealed pulmonary metastasis, leading to a decision for humane euthanasia owing to poor prognosis. Electrochemotherapy for oral MLTB in this dog demonstrated good efficacy, prolonged local control, and no regional functional impairments.