Renal Clear Cell Sarcoma

Childhood renal tumors account for 7% of all pediatric cancers. Most cases (90%) are Wilms tumor. Renal Clear Cell Sarcoma (RCCS) is a rare and very aggressive pediatric tumor characterized for its tendency to metastasize to bone often called the bone metastasis renal tumor of children. The term clear cell sarcoma relates to the presence of numerous intracytoplasmic vesicles present in the tumor histology. Other features that differentiate RCCS from Wilms tumor are that they are unicentric in the medullary region of the kidney with foci of necrosis and cyst formation. RCCS is the second most common malignant kidney tumor in children after Wilms tumor comprising approximately 4-6% of all pediatric renal tumors. RCCS is not associated with genetic predisposition syndrome and familial cases have not been reported. RCCS is rare below the age of one year, have a peak incidence between three and five years of age and are more common in males patients. Metastasis from RCCS can also occur to lymph nodes, lungs, liver and brain. RCCS occurs in the same age range as Wilms tumor with no specific radiological features to help distinguish one from the other. Grossly RCCS include large tumor size (more than 10 cm in diameter), mucoid texture, foci of necrosis and prominent cyst formation. Nine histologic different patterns of RCCS have been described. The four important prognostic factors associated with RCCS include treatment with doxorubin, beyond stage I, age at diagnosis greater than two years and tumor necrosis. Management of RCCS at all stages requires aggressive surgical approach followed by chemotherapy and radiotherapy as per NWTS-5 protocols.  Overall survival after treatment is 69%. Relapse rates are high and often occur late. Adverse prognostic factors identified are young age, advanced stage IV disease and those with relapse disease.

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