Introduction

Clear cell sarcoma of the kidney (CCSK), once considered a variant of Wilms tumor, was recognized as a distinct renal tumor of childhood in the 1970s [1][2]. Although surgical management of CCSK is guided by the same principles as Wilms, CCSK, along with anaplastic Wilms and rhabdoid tumor of the kidney, are considered to possess unfavorable histology and carry a worse prognosis relative to favorable histology Wilms [3][4]. As such, the metastatic work up, adjuvant treatment, surveillance, follow-up and clinical outcomes associated with CCSK are unique.

CCSK is a malignant tumor with an unusual tendency for bony metastasis. It generally appears as a large unifocal and unilateral tumor with a homogeneous mucoid, tan or gray/tan cut surface, often with foci of necrosis or prominent cyst formation [5][6]. Unlike WT, which compresses the margin of surrounding renal parenchyma into a pseudocapsule, CCSK invades the surrounding kidney. The classic histologic appearance is uniform oval nuclei with a delicate chromatin pattern, prominent nuclear membrane, and sparse, poorly stained vacuolated “water-clear” cytoplasm with indistinct cell membranes. Recently, a translocation t(10;17) and deletion 14q have been described in CCSK suggesting that they may play a role in its pathogenesis [7]. The cell of origin of this tumor is not known. In addition to osseous metastases, clear cell sarcomas also have a significant incidence of metastases to the brain. Clinical trials must consider results after an extended interval of follow up since as many as thirty percent of relapses occur more than two years after diagnosis [8].