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Diagnosis and Treatment of Renal Sarcoma

Renal sarcomas are rare malignant tumors of the kidney derived from mesenchymal cells.

Epidemiology

1–2% of all malignant renal tumors. Peak incidence in the fifth decade of life.

Pathology of Renal Sarcomas

Histology:

Leiomyosarcoma is the most common renal sarcoma, followed by liposarcoma. Less common sarcomas are, e.g., fibrosarcoma, rhabdomyosarcoma, osteosarcoma, malignant fibrous histiocytoma, and angiosarcoma. The pathological distinction between renal sarcoma and sarcomatoid renal cell carcinoma may be difficult.

Origin and growth:

Renal sarcomas typically arise from the organ capsule or the perisinuous space. They grow rapidly to a large size without lymphadenopathy. Due to their origin from mesenchymal cells, renal sarcomas easily cross anatomical boundaries like fascias. Although surrounded by a pseudo-capsule, the tumor may have spread beyond the capsule, explaining the frequent local recurrences after radical surgery.

Metastasis:

High-grade sarcomas metastasize most commonly to the lungs, lymph nodes, and liver.

Signs and Symptoms of Renal Sarcomas

Renal sarcomas often present with signs of an advanced tumor: flank pain, flank tumor, and hematuria. Tumor growth is fast.

Diagnostic Workup

Abdominal CT:

Large soft tissue mass originating from the kidney [fig. renal sarcoma]. Osteosarcomas show extensive calcifications and liposarcomas contain adipose tissue.

Chest CT:

To complete staging.

Abdominal CT of a large renal sarcoma (left horizontal, middle frontal and right sagittal plane). With kind permission, Prof. Dr. K. Bohndorf, Augsburg.

Differential Diagnosis

Retroperitoneal sarcoma.

Therapy of Renal Sarcomas

Radical nephrectomy:

Radical nephrectomy with en bloc resection of adjacent organs (e.g., spleen, pancreatic tail, or colon) offers the best chance for cure. Despite maximum resection, local recurrences are common, and repeat resections may be necessary.

Adjuvant radiotherapy and chemotherapy:

Adjuvant therapy is often applied since the prognosis is poor. The benefit of adjuvant therapy is not as well defined as for sarcomas of the extremity. The response rate of chemotherapy for metastatic sarcoma is low.

Prognosis

Renal sarcomas have a poor prognosis compared to sarcomas in other localizations. The grading (differentiation) and margin status after resection are significant prognostic factors. The overall 1-, 3-, and 5-year survival rate was 86%, 41%, and 15% (Wang et al., 2011). The median survival was 28 months. After two years, only 10% were free of disease. The median survival with metastases or after recurrence was 8–10 months.

References

Wang, X.; Xu, R.; Yan, L.; Zhuang, J.; Wei, B.; Kang, D.; Wu, K.; Xie, L.; Xie, Z.; Wei, Q.; Li, X.; Zeng, H. & Lu, Y. Adult renal sarcoma: clinical features and survival in a series of patients treated at a high-volume institution.
Urology 2011, 77, 836-841.

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