ABSTRACT
An 11-year-old boy experienced right flank pain on October 12, 2005. The pain was once alleviated but recurred on the following day, and the patient visited our hospital on October 13, 2005. An imaging study revealed a tumor, sized approximately 12.0 × 7.5 × 8.0 cm, in the right kidney without metastases, for which right nephrectomy was performed. The tumor was solid, although degenerative necrosis and hemorrhage were partially observed inside the tumor. A histopathological study revealed poorly-defined, almost round tumor cells which were strongly stained with vimentin but not with cytokeratin or epithelial membrane antigen (EMA). Based on these findings, a diagnosis of clear cell sarcoma of the kidney in Stage II was made. A review of 10 previous cases reported in Japan during the past 10 years revealed that the affected patients were mostly aged 1 month to 4 years, while our case, occurring in an 11-year-old patient, was uncommon in respect to age.