Renal sarcomas are rare malignant tumors of the kidney, which are derived from mesenchymal cells.
1–2% of all malignant renal tumors. Peak incidence in the fifth decade of life.
Pathology of Renal Sarcomas
Leiomyosarcomas are the most common renal sarcoma, followed by liposarcomas. 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 from 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 already have spread beyond the capsule. This explains the frequent local recurrences after radical surgery.
High-grade sarcomas metastasize most commonly to the lungs, lymph nodes and less often to the 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 very fast.
Computed tomography (CT) scans of abdomen and thorax:
CT scans reveal a large soft tissue mass originating from the kidney [fig. renal sarcoma]. Osteosarcomas show extensive calcifications and liposarcomas contain adipose tissue. Scans of the thorax are done to complete staging.
CT scans of a large renal sarcoma (left horizontal, middle frontal and right sagittal plane). By courtesy Prof. Dr. K. Bohndorf, Augsburg.
Angiography is not indicated any more for the evaluation of renal masses. Sarcomas most often present as a hypovascular mass (exception: malignant hemangiopericytoma).
Therapy of Renal Sarcomas
Radical nephrectomy with en bloc resection of adjacent organs (e.g. splen, 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 ajduvant therapy is not as well defined as for sarcomas of the extremity. The reponse rates of chemotherapy for metastatic sarcoma are low.
Renal sarcomas have a poor prognosis compared to sarcomas in other localizations. Major prognostic factors are the grading (differentiation) and margin status after resection. In the retrospective serie from Wang et al, the overall 1-, 3-, and 5-year survival rate was 86%, 41%, and 15%. 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 (Wang et al, 2011).
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- 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.
renal sarcoma: clinical features and survival in a series of patients
treated at a high-volume institution.
Urology 2011, 77, 836-841.