Soft tissue sarcomas originating from retroperitoneal cavity in a maltese dog

An 11-year-old spayed female maltese was presented for abdominal distention, dysuria and dyschezia. Panting and heart murmur was found and abdominal palpation was difficult due to increased abdominal pressure. A soft tissue mass, 6 × 3 cm in size, was identified radiographically in pelvic canal, displacing the descending colon to the medioventral direction and the urinary bladder cranially. On ultrasonography, the mass consisted of homogeneous hypoechoic parenchyma containing the focal hyperechoic region (1.6 × 1.5 cm). The mass had distinct margin and no connection with adjacent organs. It was considered as a mass originating from the retroperitoneal cavity. Additional diagnostic procedures were not advanced because of the owner’s request, and only a surgical excision of the mass was performed to alleviate the dysuria and dyschezia. Histopathologic examination and immunohistochemistry determined the mass as a soft tissue sarcoma and excluded hemangiosarcoma and osteosarcoma, both are the most common types of the retroperitoneal tumors. This report described non-vascular soft tissue sarcoma originating from the retroperitoneal cavity in a maltese dog.