Intestinal Osteosarcoma with Liver Metastasis in a Dog with a History of Recurrent Cotton-Based Toy Fragment Ingestion.

Canine extraskeletal osteosarcomas are mesenchymal, osteoid producing tumors that can arise in soft tissues without initial involvement of the bones. An 8-year-old intact male Beagle dog presented with anorexia, abdominal pain, intermittent vomiting and melena. The patient had a history of recurrent ingestion of cotton based-toy fragments, but no prior surgical procedures involving the abdominal cavity. During the exploratory laparotomy, a mass was identified in the jejunal wall. Surgical resection was performed, and tissue samples were collected for pathological examination. Histologically, the mass was diagnosed as osteoblastic osteosarcoma with fragments of cotton fiber material. The neoplastic cells were immunolabeled for vimentin and BMP-2, further supporting the morphological diagnosis. Seven months after the surgery, metastatic nodules were identified in the liver. The dog died ten months after intestinal mass resection. This case represents the first documented instance of metastatic intestinal osteosarcoma potentially caused by ingestion of cotton fiber material.