Surgical Management of Recurrent Rib-Origin Multilobular Osteochondrosarcoma with Pulmonary Metastasis in a Dog: A Case Report

Multilobular osteochondrosarcoma (MLO) is an uncommon canine primary bone tumor that typically arises from the flat bones of the skull, whereas rib involvement is rarely reported. A 13-year-old castrated male mixed-breed dog was referred for recurrence of a previously resected grade 2 MLO originating from the left 12th rib. Imaging revealed the recurrent rib mass together with a 2.1 × 1.5 × 1.7 cm mass in the right caudal lung lobe and additional pulmonary micronodules. The dog underwent combined surgical treatment consisting of en bloc resection of the recurrent mass with the 11th–13th ribs, thoracic wall reconstruction by diaphragmatic advancement, and complete lobectomy of the affected lung lobe. Histopathology confirmed grade 3 MLO with pulmonary metastasis. Postoperative anticancer drug sensitivity testing guided the selection of an oral tyrosine kinase inhibitor. The dog recovered without major complications, and at the 3-month postoperative follow-up, physical examination revealed no evidence of local recurrence, while thoracic radiography showed no new radiographically detectable pulmonary lesions. This case describes en bloc resection of recurrent rib-origin MLO combined with resection of the dominant pulmonary metastatic lesion in a dog, with no clinically detectable local recurrence or new radiographically detectable pulmonary lesions during the 3-month follow-up period. Although the short follow-up precludes conclusions regarding long-term efficacy, this report contributes clinically relevant information on the surgical management and short-term outcome of this rare condition.