+ General Considerations

  • Retroperitoneal sarcomas are defined as mesenchymal tumors originating from within the retroperitoneal space but not including neoplasms arising from retroperitoneal organs, such as the adrenal glands, kidneys, and ureters
  • HSA is the most common retroperitoneal sarcoma in dogs (64%, 9/14), with others including OSA, peripheral nerve sheath tumor, and leiomyosarcoma
  • Majority of dogs with retroperitoneal sarcomas have a high histologic grade (grade III in 57%) and clinical stage
  • 50% (7/14) retroperitoneal sarcomas are invasive into structures such as the kidney, adrenal glands, aorta, caudal vena cava, and paraspinal muscles
  • Metastasis is present in 29% (4/14) dogs at diagnosis and 71% (10/14) dogs at death
  • Lungs are the most common site of metastasis, and other sites include peritoneum, intestines, liver, heart, and brain

+ Clinical Features

  • Large breed dogs with a median weight of 27.7 kg
  • Median age 9 years
  • Clinical signs are either non-specific or neurologic
  • Non-specific signs include inappetence, lethargy or collapse, and weight loss
  • Neurologic signs include LMN pelvic limb lameness and neurogenic urinary incontinence
  • Hematology: anemia is common (71.4%) with other abnormalities including leukocytosis, lymphopenia, neutrophilia, thrombocytopenia, and red blood cell morphologic abnormalities
  • Serum biochemistry: AST and creatine kinase were increased in ≥ 50% dogs
  • Diagnosis: retroperitoneal mass is readily evident on abdominal imaging using survey radiographs, ultrasound, or CT

+ Treatment

  • Exploratory celiotomy and surgical resection
  • ± Radiation therapy in either a preoperative, intraoperative, or postoperative setting
  • ± Adjuvant chemotherapy

+ Prognosis

  • Prognosis is poor with 37.5 day MST and tumor-related deaths in 93% (13/14) dogs (range, 2-498 days)
  • Local tumor recurrence in 14% (2/14) dogs and tumor progression in 43% (6/14) dogs
  • Metastasis is present in 29% (4/14) dogs at diagnosis and 71% (10/14) dogs at death
  • Prognosis for retroperitoneal sarcoma is also poor in humans with prognostic factors include tumor grade and ability to achieve complete microscopic and macroscopic surgical resection
  • 5-year survival rate of 69%-92% for grade I retroperitoneal sarcomas is significantly better than 16%-48% for grade II and III retroperitoneal sarcomas
  • Complete excision results in a significant survival benefit with a 41-103 month MST and 43%-72% 5-year survival rate compared to 9-18 months and 3%-33%, respectively, following incomplete resection