Clear Cell Sarcoma of Kidney : Introduction
Introduction: Clear cell sarcoma of kidney (CCSK) is a rare malignant mesenchymal neoplasm that is seen predominantly in pediatric patients. Although rare, it is the second most common pediatric renal tumor after Wilms tumor. It is characterized by aggressive behavior, late recurrences, and a tendency to metastasize to bones (hence the previous name - bone metastasizing renal tumor of childhood). The cell of origin is still a mystery, but it is thought to arise from a non-organ-specific mesenchymal cell. It shows diverse morphologic patterns which have no prognostic significance. It is distinct from and should not be confused with clear cell sarcoma of soft tissues. Discovery of two specific, mutually exclusive genetic alterations has greatly improved diagnostic accuracy. About 85% of cases show internal tandem duplications in BCL-6 coreceptor (BCOR). Another 10% of cases have a translocation t(10;17) creating the fusion gene YWHAE-NUTM2B/E. The remaining 5% carry neither genetic alteration. The image shows classic pattern of CCSK consisting of nests of small uniform polygonal to ovoid cells with clear cytoplasm, separated by fibrovascular septae.