Primary renal sarcoma in adults are rare, representing approximately 1% of all primary tumors of the kidney. Sarcomatoid components can be seen in approximately 5% of RCC, including clear cell, papillary, chromophobe, and CDCs. It should not be confused with primary renal sarcomas, as the two entities have entirely different biology, pathology, and clinical features.
Pathology
Any sarcomas that arise in other parts of the body can occur in the kidney, including leiomyosarcoma, osteosarcoma, malignant fibrous histiocytoma (MFH), angiosarcoma, rhabdomyosarcoma, and synovial sarcoma. As in other parts of the body, the diagnosis, and classification are traditionally based on H&E histology and immunohistochemistry. However, molecular studies have been increasingly used in the classification of sarcomas. For example, synovial sarcoma of the kidney, has a characteristic chromosomal translocation t (X;18) between the SYT gene on chromosome 18 and a member of the SSX family gene on chromosome X. Leiomyosarcoma constitutes the majority of primary renal sarcomas, and fewer than 50 cases of renal MFH have been described. Tumor grade, which is recognized as an important prognostic factor in soft tissue sarcomas, is also believed to be prognostic in primary renal sarcomas.
Clinical Presentation
Pain and a palpable mass are the most common presenting complaints. They can spread along tissue spaces and attain a large size before they are symptomatic, similar to retroperitoneal sarcomas. Gross hematuria may be present. Systemic symptoms are less commonly reported. The prevalence of primary renal sarcomas increases with age. Metastasis is generally hematogenous to involve the lungs, liver, and bone. CT and MRI scans are used in the evaluation of these tumors to define the local extent, vascular relations, and involvement of adjacent organs. Preoperative radiographic imaging of the chest should also be performed since this is one of the most common sites of metastatic disease.
Treatment and Prognosis
Complete surgical excision is the mainstay of treatment of soft tissue sarcomas at any location. Adjuvant radiation therapy, although used in locally extensive disease, has not been proven to prevent local recurrence or increase survival. The use of adjuvant chemotherapy in sarcomas other than extremity sarcomas is still experimental. Because of the rarity of this disease in the kidney, the role of either chemotherapy or radiation should be considered investigational. On the basis of case reports, complete surgical extirpation of the organ-confined tumor appears to offer patients the only reasonable chance for prolonged survival. The best outcome is seen with small tumors (<5cm) of low histological grade that are confined to the kidneys. Surgical resection of locally recurrent or oligo-metastatic disease may be beneficial in select patients.
Pathology
Any sarcomas that arise in other parts of the body can occur in the kidney, including leiomyosarcoma, osteosarcoma, malignant fibrous histiocytoma (MFH), angiosarcoma, rhabdomyosarcoma, and synovial sarcoma. As in other parts of the body, the diagnosis, and classification are traditionally based on H&E histology and immunohistochemistry. However, molecular studies have been increasingly used in the classification of sarcomas. For example, synovial sarcoma of the kidney, has a characteristic chromosomal translocation t (X;18) between the SYT gene on chromosome 18 and a member of the SSX family gene on chromosome X. Leiomyosarcoma constitutes the majority of primary renal sarcomas, and fewer than 50 cases of renal MFH have been described. Tumor grade, which is recognized as an important prognostic factor in soft tissue sarcomas, is also believed to be prognostic in primary renal sarcomas.
Clinical Presentation
Pain and a palpable mass are the most common presenting complaints. They can spread along tissue spaces and attain a large size before they are symptomatic, similar to retroperitoneal sarcomas. Gross hematuria may be present. Systemic symptoms are less commonly reported. The prevalence of primary renal sarcomas increases with age. Metastasis is generally hematogenous to involve the lungs, liver, and bone. CT and MRI scans are used in the evaluation of these tumors to define the local extent, vascular relations, and involvement of adjacent organs. Preoperative radiographic imaging of the chest should also be performed since this is one of the most common sites of metastatic disease.
Treatment and Prognosis
Complete surgical excision is the mainstay of treatment of soft tissue sarcomas at any location. Adjuvant radiation therapy, although used in locally extensive disease, has not been proven to prevent local recurrence or increase survival. The use of adjuvant chemotherapy in sarcomas other than extremity sarcomas is still experimental. Because of the rarity of this disease in the kidney, the role of either chemotherapy or radiation should be considered investigational. On the basis of case reports, complete surgical extirpation of the organ-confined tumor appears to offer patients the only reasonable chance for prolonged survival. The best outcome is seen with small tumors (<5cm) of low histological grade that are confined to the kidneys. Surgical resection of locally recurrent or oligo-metastatic disease may be beneficial in select patients.