Grade III Renal Soft Tissue Sarcoma in a Dog: Surgical Treatment

Abstract

Background: Primary renal neoplasms, which are rare in dogs, typically affect middle-aged to older animals. Such neoplasms show predominantly malignant behavior, and metastases may be present. They can originate from epithelial, mesenchymal, or mixed embryonal tissues. Diagnosis can be made based on clinical signs, laboratory findings, and imaging studies; however, definitive diagnosis is obtained through histopathological examination. The recommended treatment is nephrectomy, which involves the removal of the affected kidney and ureter. Prognosis ranges from guarded to poor. The objective of this study was to describe a case of grade III renal soft tissue sarcoma treated via nephrectomy.

Case: A 6-year-old male undefined breed intact dog, weighing 19.8 kg, was referred to the Veterinary Hospital of the Federal University of Rio Grande do Sul (HCV-UFRGS) with a history of hematuria, vomiting, and hyporexia. An earlier ultrasound examination had revealed an expansive mass located in the left kidney, which showed exponential growth during the assessed period and exhibited vascularization upon Doppler imaging. The patient was referred for radical nephrectomy, during which the renal neoplasm with adhesions and neovascularization was observed. After dissection and release of the adhesions, the left kidney and ureter were removed, and the tissue was sent for histopathological analysis, resulting in a definitive diagnosis of grade III renal soft tissue sarcoma. The patient remains stable and is under periodic and continuous oncological and nephrological monitoring.

Discussion: According to the literature, primary renal neoplasms such as the one identified in this patient are rare in dogs. On the other hand, secondary renal neoplasms are more common, occurring approximately twice as frequently. This disparity is attributed to the high renal blood flow and extensive capillary network, which increase the kidneys’ susceptibility to metastatic tumor implantation. The clinical profile, laboratory findings, and imaging results of the patient in this case align with characteristics described in the literature for primary renal neoplasms in canines. Age is a relevant factor for the development of primary renal neoplasms, with older animals being more commonly affected. Nephrectomy, the treatment of choice in these cases, was performed successfully, and no significant postoperative complications occurred. Despite the absence of advanced imaging techniques, serial ultrasonography played a crucial role in monitoring tumor growth and planning the surgical approach. The histopathological diagnosis of grade III sarcoma, combined with the high mitotic index detected, indicates a guarded prognosis, even in the absence of detectable metastases. The absence of recurrence and metastases up to 70 days post-surgery is encouraging, but does not rule out the possibility of future recurrence, especially considering the aggressive nature of the neoplasm. In addition to surgical treatment, a multimodal approach combining nephrectomy and chemotherapy has been studied in recent years. However, studies that prove its efficacy are still scant, as is statistical evidence recommending its use in these patients, since, to date, adjuvant chemotherapy has not shown an increase in survival rates. Although chemotherapy was considered, its efficacy remains inconclusive in veterinary literature, and its exclusion in this case aligns with the most commonly adopted approach, given the lack of robust data supporting a proven benefit. In the case described here, the patient did not undergo chemotherapy, and the only therapeutic approach employed was nephrectomy, whose outcome has been successful up to the moment of this writing.

Keywords: nephrectomy, primary renal neoplasm, canine, sarcoma.

Título: Sarcoma de tecidos moles renal grau III em um cão: tratamento cirúrgico

Descritores: nefrectomia, neoplasia renal primária, canino, sarcoma.